FLTK 1.4.0: Drawing functions

FLTK global graphics and GUI drawing functions. More...

Enumerations
enum	{ FL_SOLID = 0 , FL_DASH = 1 , FL_DOT = 2 , FL_DASHDOT = 3 , FL_DASHDOTDOT = 4 , FL_CAP_FLAT = 0x100 , FL_CAP_ROUND = 0x200 , FL_CAP_SQUARE = 0x300 , FL_JOIN_MITER = 0x1000 , FL_JOIN_ROUND = 0x2000 , FL_JOIN_BEVEL = 0x3000 }
	More...

Functions
int	fl_add_symbol (const char name, void(drawit)(Fl_Color), int scalable)
	Adds a symbol to the system. More...

int	fl_antialias ()
	Return whether line drawings are currently antialiased.

void	fl_antialias (int state)
	Turn antialiased line drawings ON or OFF, if supported by platform. More...

void	fl_arc (double x, double y, double r, double start, double end)
	Add a series of points to the current path on the arc of a circle. More...

void	fl_arc (int x, int y, int w, int h, double a1, double a2)
	Draw ellipse sections using integer coordinates. More...

void	fl_begin_complex_polygon ()
	Start drawing a complex filled polygon. More...

void	fl_begin_line ()
	Start drawing a list of lines.

void	fl_begin_loop ()
	Start drawing a closed sequence of lines.

void	fl_begin_offscreen (Fl_Offscreen ctx)
	Send all subsequent drawing commands to this offscreen buffer. More...

void	fl_begin_points ()
	Start drawing a list of points. More...

void	fl_begin_polygon ()
	Start drawing a convex filled polygon.

char	fl_can_do_alpha_blending ()
	Check whether platform supports true alpha blending for RGBA images. More...

Fl_RGB_Image *	fl_capture_window (Fl_Window *win, int x, int y, int w, int h)
	Captures the content of a rectangular zone of a mapped window. More...

void	fl_chord (int x, int y, int w, int h, double a1, double a2)
	fl_chord declaration is a place holder - the function does not yet exist

void	fl_circle (double x, double y, double r)
	fl_circle(x,y,r) is equivalent to fl_arc(x,y,r,0,360), but may be faster. More...

void	fl_clip (int x, int y, int w, int h)
	Intersect the current clip region with a rectangle and push this new region onto the stack (deprecated). More...

int	fl_clip_box (int x, int y, int w, int h, int &X, int &Y, int &W, int &H)
	Intersect a rectangle with the current clip region and return the bounding box of the result. More...

Fl_Region	fl_clip_region ()
	Return the current clipping region. More...

void	fl_clip_region (Fl_Region r)
	Replace the top of the clipping stack with a clipping region of any shape. More...

void	fl_copy_offscreen (int x, int y, int w, int h, Fl_Offscreen pixmap, int srcx, int srcy)
	Copy a rectangular area of the given offscreen buffer into the current drawing destination. More...

Fl_Offscreen	fl_create_offscreen (int w, int h)
	Creation of an offscreen graphics buffer. More...

void	fl_cursor (Fl_Cursor)
	Sets the cursor for the current window to the specified shape and colors. More...

void	fl_cursor (Fl_Cursor, Fl_Color fg, Fl_Color bg=FL_WHITE)

void	fl_curve (double X0, double Y0, double X1, double Y1, double X2, double Y2, double X3, double Y3)
	Add a series of points on a Bézier curve to the path. More...

void	fl_delete_offscreen (Fl_Offscreen ctx)
	Deletion of an offscreen graphics buffer. More...

void	fl_draw (const char *str, int n, int x, int y)
	Draws starting at the given `x`, `y` location a UTF-8 string of length `n` bytes.

void	fl_draw (const char *str, int x, int y)
	Draw a nul-terminated UTF-8 string starting at the given `x`, `y` location. More...

void	fl_draw (const char str, int x, int y, int w, int h, Fl_Align align, Fl_Image img=0, int draw_symbols=1, int spacing=0)
	Fancy string drawing function which is used to draw all the labels. More...

void	fl_draw (const char str, int x, int y, int w, int h, Fl_Align align, void(callthis)(const char , int, int, int), Fl_Image img=0, int draw_symbols=1, int spacing=0)
	The same as fl_draw(const char,int,int,int,int,Fl_Align,Fl_Image,int) with the addition of the `callthis` parameter, which is a pointer to a text drawing function such as fl_draw(const char*, int, int, int) to do the real work. More...

void	fl_draw (int angle, const char *str, int n, int x, int y)
	Draw at the given `x`, `y` location a UTF-8 string of length `n` bytes rotating `angle` degrees counter-clockwise. More...

void	fl_draw (int angle, const char *str, int x, int y)
	Draw a nul-terminated UTF-8 string starting at the given `x`, `y` location and rotating `angle` degrees counter-clockwise. More...

void	fl_draw_arrow (Fl_Rect bb, Fl_Arrow_Type t, Fl_Orientation o, Fl_Color color)
	Draw an "arrow like" GUI element for the selected scheme. More...

void	fl_draw_box (Fl_Boxtype, int x, int y, int w, int h, Fl_Color)
	Draws a box using given type, position, size and color. More...

void	fl_draw_box_focus (Fl_Boxtype, int x, int y, int w, int h, Fl_Color, Fl_Color)
	Draws the focus rectangle inside a box using given type, position, size and color. More...

void	fl_draw_check (Fl_Rect bb, Fl_Color col)
	Draw a check mark inside the given bounding box. More...

void	fl_draw_circle (int x, int y, int d, Fl_Color color)
	Draw a potentially small, filled circle using a given color. More...

void	fl_draw_image (const uchar *buf, int X, int Y, int W, int H, int D=3, int L=0)
	Draw an 8-bit per color RGB or luminance image. More...

void	fl_draw_image (Fl_Draw_Image_Cb cb, void *data, int X, int Y, int W, int H, int D=3)
	Draw an image using a callback function to generate image data. More...

void	fl_draw_image_mono (const uchar *buf, int X, int Y, int W, int H, int D=1, int L=0)
	Draw a gray-scale (1 channel) image. More...

void	fl_draw_image_mono (Fl_Draw_Image_Cb cb, void *data, int X, int Y, int W, int H, int D=1)
	Draw a gray-scale image using a callback function to generate image data. More...

int	fl_draw_pixmap (char const data, int x, int y, Fl_Color bg=FL_GRAY)
	Draw XPM image data, with the top-left corner at the given position. More...

int	fl_draw_pixmap (const char const data, int x, int y, Fl_Color bg=FL_GRAY)
	Draw XPM image data, with the top-left corner at the given position. More...

void	fl_draw_radio (int x, int y, int d, Fl_Color color)
	Draw a round check mark (circle) of a radio button. More...

int	fl_draw_symbol (const char *label, int x, int y, int w, int h, Fl_Color)
	Draw the named symbol in the given rectangle using the given color. More...

void	fl_end_complex_polygon ()
	End complex filled polygon, and draw.

void	fl_end_line ()
	End list of lines, and draw.

void	fl_end_loop ()
	End closed sequence of lines, and draw.

void	fl_end_offscreen ()
	Quit sending drawing commands to the current offscreen buffer.

void	fl_end_points ()
	End list of points, and draw.

void	fl_end_polygon ()
	End convex filled polygon, and draw.

const char *	fl_expand_text (const char from, char buf, int maxbuf, double maxw, int &n, double &width, int wrap, int draw_symbols=0)
	Copy `from` to `buf`, replacing control characters with ^X. More...

void	fl_focus_rect (int x, int y, int w, int h)
	Draw a dotted rectangle, used to indicate keyboard focus on a widget. More...

void	fl_frame (const char *s, int x, int y, int w, int h)
	Draws a series of line segments around the given box. More...

void	fl_frame2 (const char *s, int x, int y, int w, int h)
	Draws a series of line segments around the given box. More...

void	fl_gap ()
	Separate loops of the path. More...

void	fl_line (int x, int y, int x1, int y1)
	Draw a line from (x,y) to (x1,y1)

void	fl_line (int x, int y, int x1, int y1, int x2, int y2)
	Draw a line from (x,y) to (x1,y1) and another from (x1,y1) to (x2,y2)

void	fl_line_style (int style, int width=0, char *dashes=0)
	Set how to draw lines (the "pen"). More...

void	fl_load_identity ()
	Set the transformation matrix to identity.

void	fl_load_matrix (double a, double b, double c, double d, double x, double y)
	Set the current transformation matrix. More...

void	fl_loop (int x, int y, int x1, int y1, int x2, int y2)
	Outline a 3-sided polygon with lines.

void	fl_loop (int x, int y, int x1, int y1, int x2, int y2, int x3, int y3)
	Outline a 4-sided polygon with lines.

void	fl_measure (const char *str, int &x, int &y, int draw_symbols=1)
	Measure how wide and tall the string will be when printed by the fl_draw() function with `align` parameter. More...

int	fl_measure_pixmap (char const data, int &w, int &h)
	Get the dimensions of a pixmap. More...

int	fl_measure_pixmap (const char const cdata, int &w, int &h)
	Get the dimensions of a pixmap. More...

void	fl_mult_matrix (double a, double b, double c, double d, double x, double y)
	Concatenate another transformation onto the current one. More...

int	fl_not_clipped (int x, int y, int w, int h)
	Does the rectangle intersect the current clip region? More...

unsigned int	fl_old_shortcut (const char *s)
	Emulation of XForms named shortcuts. More...

void	fl_overlay_clear ()
	Erase a selection rectangle without drawing a new one. More...

void	fl_overlay_rect (int x, int y, int w, int h)
	Draw a transient dotted selection rectangle. More...

float	fl_override_scale ()
	Removes any GUI scaling factor in subsequent drawing operations. More...

void	fl_pie (int x, int y, int w, int h, double a1, double a2)
	Draw filled ellipse sections using integer coordinates. More...

void	fl_point (int x, int y)
	Draw a single pixel at the given coordinates.

void	fl_polygon (int x, int y, int x1, int y1, int x2, int y2)
	Fill a 3-sided polygon.

void	fl_polygon (int x, int y, int x1, int y1, int x2, int y2, int x3, int y3)
	Fill a 4-sided polygon. More...

void	fl_pop_clip ()
	Restore the previous clip region. More...

void	fl_pop_matrix ()
	Restore the current transformation matrix from the stack.

void	fl_push_clip (int x, int y, int w, int h)
	Intersect the current clip region with a rectangle and push this new region onto the stack. More...

void	fl_push_matrix ()
	Save the current transformation matrix on the stack. More...

void	fl_push_no_clip ()
	Push an empty clip region onto the stack so nothing will be clipped.

uchar *	fl_read_image (uchar *p, int X, int Y, int W, int H, int alpha=0)
	Reads an RGB(A) image from the current window or off-screen buffer. More...

void	fl_rect (Fl_Rect r)
	Draw a border inside the given bounding box. More...

void	fl_rect (int x, int y, int w, int h)
	Draw a border inside the given bounding box. More...

void	fl_rect (int x, int y, int w, int h, Fl_Color c)
	Draw with passed color a border inside the given bounding box. More...

void	fl_rectf (Fl_Rect bb, uchar r, uchar g, uchar b)
	Color a rectangle with "exactly" the passed `r,g,b` color. More...

void	fl_rectf (Fl_Rect r)
	Color with current color a rectangle that exactly fills the given bounding box.

void	fl_rectf (Fl_Rect r, Fl_Color c)
	Color with passed color a rectangle that exactly fills the given bounding box. More...

void	fl_rectf (int x, int y, int w, int h)
	Color with current color a rectangle that exactly fills the given bounding box.

void	fl_rectf (int x, int y, int w, int h, Fl_Color c)
	Color with passed color a rectangle that exactly fills the given bounding box. More...

void	fl_rectf (int x, int y, int w, int h, uchar r, uchar g, uchar b)
	Color a rectangle with "exactly" the passed `r,g,b` color. More...

void	fl_rescale_offscreen (Fl_Offscreen &ctx)
	Adapts an offscreen buffer to a changed value of the scale factor. More...

void	fl_reset_spot (void)
	Resets marked text. More...

void	fl_restore_clip ()
	Undo any clobbering of the clip region done by your program.

void	fl_restore_scale (float s)
	Restores the GUI scaling factor and the clipping region in subsequent drawing operations. More...

void	fl_rotate (double d)
	Concatenate rotation transformation onto the current one. More...

void	fl_rounded_rect (int x, int y, int w, int h, int r)
	Draw a rounded border inside the given bounding box. More...

void	fl_rounded_rectf (int x, int y, int w, int h, int r)
	Color with current color a rounded rectangle that exactly fills the given bounding box. More...

void	fl_rtl_draw (const char *str, int n, int x, int y)
	Draw a UTF-8 string of length `n` bytes right to left starting at the given `x`, `y` location.

void	fl_scale (double x)
	Concatenate scaling transformation onto the current one. More...

void	fl_scale (double x, double y)
	Concatenate scaling transformation onto the current one. More...

void	fl_scroll (int X, int Y, int W, int H, int dx, int dy, void(draw_area)(void , int, int, int, int), void *data)
	Scroll a rectangle and draw the newly exposed portions. More...

void	fl_set_spot (int font, int size, int X, int Y, int W, int H, Fl_Window *win=0)
	Inform text input methods about the current text insertion cursor. More...

void	fl_set_status (int X, int Y, int W, int H)
	Related to text input methods under X11. More...

const char *	fl_shortcut_label (unsigned int shortcut)
	Get a human-readable string from a shortcut value. More...

const char *	fl_shortcut_label (unsigned int shortcut, const char **eom)
	Get a human-readable string from a shortcut value. More...

double	fl_transform_dx (double x, double y)
	Transform distance using current transformation matrix. More...

double	fl_transform_dy (double x, double y)
	Transform distance using current transformation matrix. More...

double	fl_transform_x (double x, double y)
	Transform coordinate using the current transformation matrix. More...

double	fl_transform_y (double x, double y)
	Transform coordinate using the current transformation matrix. More...

void	fl_transformed_vertex (double xf, double yf)
	Add coordinate pair to the vertex list without further transformations. More...

void	fl_translate (double x, double y)
	Concatenate translation transformation onto the current one. More...

void	fl_vertex (double x, double y)
	Add a single vertex to the current path. More...

void	fl_xyline (int x, int y, int x1)
	Draw a horizontal line from (x,y) to (x1,y).

void	fl_xyline (int x, int y, int x1, int y2)
	Draw a horizontal line from (x,y) to (x1,y), then vertical from (x1,y) to (x1,y2).

void	fl_xyline (int x, int y, int x1, int y2, int x3)
	Draw a horizontal line from (x,y) to (x1,y), then a vertical from (x1,y) to (x1,y2) and then another horizontal from (x1,y2) to (x3,y2).

void	fl_yxline (int x, int y, int y1)
	Draw a vertical line from (x,y) to (x,y1)

void	fl_yxline (int x, int y, int y1, int x2)
	Draw a vertical line from (x,y) to (x,y1), then a horizontal from (x,y1) to (x2,y1).

void	fl_yxline (int x, int y, int y1, int x2, int y3)
	Draw a vertical line from (x,y) to (x,y1), then a horizontal from (x,y1) to (x2,y1), then another vertical from (x2,y1) to (x2,y3).

Detailed Description

FLTK global graphics and GUI drawing functions.

These functions are declared in <FL/fl_draw.H>, and in <FL/platform.H> for offscreen buffer-related ones.

Enumeration Type Documentation

◆ anonymous enum

anonymous enum

fl_line_style() styles

Enumerator
FL_SOLID	line style: solid line
FL_DASH	line style: 75% dashed line
FL_DOT	line style: 50% pixel dotted
FL_DASHDOT	line style: dash / dot pattern
FL_DASHDOTDOT	line style: dash / two dot pattern
FL_CAP_FLAT	cap style: end is flat
FL_CAP_ROUND	cap style: end is round
FL_CAP_SQUARE	cap style: end wraps end point
FL_JOIN_MITER	join style: line join extends to a point
FL_JOIN_ROUND	join style: line join is rounded
FL_JOIN_BEVEL	join style: line join is tidied

Function Documentation

◆ fl_add_symbol()

int fl_add_symbol	(	const char *	name,
		void(*)(Fl_Color)	drawit,
		int	scalable
	)

Adds a symbol to the system.

Parameters

[in]	name	name of symbol (without the "@")
[in]	drawit	function to draw symbol
[in]	scalable	set to 1 if `drawit` uses scalable vector drawing

Returns: 1 on success, 0 on failure

◆ fl_antialias()

void fl_antialias ( int state )

inline

Turn antialiased line drawings ON or OFF, if supported by platform.

Currently, only the Windows platform allows to change whether line drawings are antialiased. Turning it OFF may accelerate heavy drawing operations.

◆ fl_arc() [1/2]

void fl_arc	(	double	x,
		double	y,
		double	r,
		double	start,
		double	end
	)

inline

Add a series of points to the current path on the arc of a circle.

The arc is drawn counter-clockwise from 3 o'clock. If end is less than start then it draws the arc in a clockwise direction. To draw an arc across the 3 o'clock line, start and end can be greater than 360 or less than 0. For example, to draw a counter-clockwise arc from 6 to 12 o'clock, start would be -90 deg, and end would be at +90 deg.

You can get elliptical paths by using scale and rotate before calling fl_arc().

Parameters

[in]	x,y,r	center and radius of circular arc
[in]	start,end	angles of start and end of arc measured in degrees

fl_arc(x,y,r,a1,a2)

Examples:

// Draw an arc of points
fl_begin_points();
fl_arc(100.0, 100.0, 50.0, 0.0, 180.0);
fl_end_points();
 
// Draw arc with a line
fl_begin_line();
fl_arc(200.0, 100.0, 50.0, 0.0, 180.0);
fl_end_line();
 
// Draw filled arc
fl_begin_polygon();
fl_arc(300.0, 100.0, 50.0, 0.0, 180.0);
fl_end_polygon();

◆ fl_arc() [2/2]

void fl_arc	(	int	x,
		int	y,
		int	w,
		int	h,
		double	a1,
		double	a2
	)

inline

Draw ellipse sections using integer coordinates.

These functions match the rather limited circle drawing code provided by X and Windows. The advantage over using fl_arc with floating point coordinates is that they are faster because they often use the hardware, and they draw much nicer small circles, since the small sizes are often hard-coded bitmaps.

If a complete circle is drawn it will fit inside the passed bounding box. The two angles are measured in degrees counter-clockwise from 3 o'clock and are the starting and ending angle of the arc, a2 must be greater or equal to a1.

fl_arc() draws a series of lines to approximate the arc. Notice that the integer version of fl_arc() has a different number of arguments than the double version fl_arc(double x, double y, double r, double start, double end)

Parameters

[in]	x,y,w,h	bounding box of complete circle
[in]	a1,a2	start and end angles of arc measured in degrees counter-clockwise from 3 o'clock. `a2` must be greater than or equal to `a1`.

fl_pie() and fl_arc()

◆ fl_begin_complex_polygon()

void fl_begin_complex_polygon ( )

inline

Start drawing a complex filled polygon.

The polygon may be concave, may have holes in it, or may be several disconnected pieces. Call fl_gap() to separate loops of the path.

To outline the polygon, use fl_begin_loop() and replace each fl_gap() with fl_end_loop();fl_begin_loop() pairs.

Note: For portability, you should only draw polygons that appear the same whether "even/odd" or "non-zero" winding rules are used to fill them. Holes should be drawn in the opposite direction to the outside loop.

◆ fl_begin_offscreen()

void fl_begin_offscreen ( Fl_Offscreen ctx )

Send all subsequent drawing commands to this offscreen buffer.

Parameters

ctx	the offscreen buffer.

Note: The ctx argument must have been created by fl_create_offscreen().

◆ fl_begin_points()

void fl_begin_points ( )

inline

Start drawing a list of points.

Points are added to the list with fl_vertex().

◆ fl_can_do_alpha_blending()

char fl_can_do_alpha_blending ( )

inline

Check whether platform supports true alpha blending for RGBA images.

Returns: 1 if true alpha blending supported by platform; 0 not supported so FLTK will use screen door transparency

◆ fl_capture_window()

Fl_RGB_Image * fl_capture_window	(	Fl_Window *	win,
		int	x,
		int	y,
		int	w,
		int	h
	)

Captures the content of a rectangular zone of a mapped window.

Parameters

win	a mapped Fl_Window (derived types including Fl_Gl_Window are also possible)
x,y,w,h	window area to be captured. Intersecting sub-windows are captured too.

Returns: The captured pixels as an Fl_RGB_Image. The raw and drawing sizes of the image can differ. Returns NULL when capture was not successful. The image depth may differ between platforms.

Version: 1.4

◆ fl_circle()

void fl_circle	(	double	x,
		double	y,
		double	r
	)

inline

fl_circle(x,y,r) is equivalent to fl_arc(x,y,r,0,360), but may be faster.

Parameters

[in] x,y,r center and radius of circle

Note: fl_circle() is best used as part of the Drawing Complex Shapes API, that is, flanked by fl_begin_XXX() and fl_end_XXX() calls where XXX can be 'loop' or 'polygon' to draw, respectively a circle or a disk. Transformation functions (e.g., fl_scale(double, double)) can be also used for fl_circle() to draw empty of filled ellipses. It must be the only thing in the path: if you want a circle as part of a complex polygon you must use fl_arc().
Nevertheless, fl_circle() can also be used by itself to draw circles.

◆ fl_clip()

void fl_clip	(	int	x,
		int	y,
		int	w,
		int	h
	)

inline

Intersect the current clip region with a rectangle and push this new region onto the stack (deprecated).

Parameters

[in] x,y,w,h position and size

Deprecated:: Please use fl_push_clip(int x, int y, int w, int h) instead. fl_clip(int, int, int, int) will be removed in FLTK 1.5.

◆ fl_clip_box()

int fl_clip_box	(	int	x,
		int	y,
		int	w,
		int	h,
		int &	X,
		int &	Y,
		int &	W,
		int &	H
	)

inline

Intersect a rectangle with the current clip region and return the bounding box of the result.

Returns non-zero if the resulting rectangle is different to the original. The given rectangle (x, y, w, h) should be entirely inside its window, otherwise the result may be unexpected, i.e. this function may not clip the rectangle to the window coordinates and size. In particular x and y should not be negative.

The resulting bounding box can be used to limit the necessary drawing to this rectangle.

Example:

void MyGroup::draw() {
  int X = 0, Y = 0, W = 0, H = 0;
  int ret = fl_clip_box(x(), y(), w(), h(), X, Y, W, H);
  if (ret == 0) { // entire group is visible (not clipped)
    // full drawing code here
  } else { // parts of this group are clipped
    // partial drawing code here (uses X, Y, W, and H to test)
  }
}

W and H are set to zero if the rectangle is completely outside the clipping region. In this case X and Y are undefined and should not be used. Possible values are (0, 0), (x, y), or anything else (platform dependent).

Note: This function is platform-dependent. If the given rectangle is not entirely inside the window, the results are not guaranteed to be the same on all platforms.

Parameters

[in]	x,y,w,h	position and size of rectangle
[out]	X,Y,W,H	position and size of resulting bounding box.

Returns: Non-zero if the resulting rectangle is different to the original.

See also: fl_not_clipped()

◆ fl_clip_region() [1/2]

Fl_Region fl_clip_region ( )

inline

Return the current clipping region.

Note: This function is mostly intended for internal use by the FLTK library when drawing to the display. Its return value can be always NULL if the current drawing surface is not the display.

◆ fl_clip_region() [2/2]

void fl_clip_region ( Fl_Region r )

inline

Replace the top of the clipping stack with a clipping region of any shape.

Fl_Region is an operating system specific type.

Note: This function is mostly intended for internal use by the FLTK library when drawing to the display. Its effect can be null if the current drawing surface is not the display.

Parameters

[in] r clipping region

◆ fl_copy_offscreen()

void fl_copy_offscreen	(	int	x,
		int	y,
		int	w,
		int	h,
		Fl_Offscreen	pixmap,
		int	srcx,
		int	srcy
	)

inline

Copy a rectangular area of the given offscreen buffer into the current drawing destination.

Parameters

x,y	position where to draw the copied rectangle
w,h	size of the copied rectangle
pixmap	offscreen buffer containing the rectangle to copy
srcx,srcy	origin in offscreen buffer of rectangle to copy

◆ fl_create_offscreen()

Fl_Offscreen fl_create_offscreen	(	int	w,
		int	h
	)

Creation of an offscreen graphics buffer.

Parameters

w,h	width and height in FLTK units of the buffer.

Returns: the created graphics buffer.

The pixel size of the created graphics buffer is equal to the number of pixels in an area of the screen containing the current window sized at w,h FLTK units. This pixel size varies with the value of the scale factor of this screen.

Note

Work with the fl_XXX_offscreen() functions is equivalent to work with an Fl_Image_Surface object, as follows :

Fl_Offscreen-based approach	Fl_Image_Surface-based approach
Fl_Offscreen off = fl_create_offscreen(w, h)	Fl_Image_Surface *surface = new Fl_Image_Surface(w, h, 1)
fl_begin_offscreen(off)	Fl_Surface_Device::push_current(surface)
fl_end_offscreen()	Fl_Surface_Device::pop_current()
fl_copy_offscreen(x,y,w,h, off, sx,sy)	fl_copy_offscreen(x,y,w,h, surface->offscreen(), sx,sy)
fl_rescale_offscreen(off)	surface->rescale()
fl_delete_offscreen(off)	delete surface

◆ fl_cursor()

void fl_cursor ( Fl_Cursor c )

Sets the cursor for the current window to the specified shape and colors.

The cursors are defined in the <FL/Enumerations.H> header file.

◆ fl_curve()

void fl_curve	(	double	X0,
		double	Y0,
		double	X1,
		double	Y1,
		double	X2,
		double	Y2,
		double	X3,
		double	Y3
	)

inline

Add a series of points on a Bézier curve to the path.

The curve ends (and two of the points) are at X0,Y0 and X3,Y3.

Parameters

[in]	X0,Y0	curve start point
[in]	X1,Y1	curve control point
[in]	X2,Y2	curve control point
[in]	X3,Y3	curve end point

◆ fl_delete_offscreen()

void fl_delete_offscreen ( Fl_Offscreen ctx )

Deletion of an offscreen graphics buffer.

Parameters

ctx	the buffer to be deleted.

Note: The ctx argument must have been created by fl_create_offscreen().

◆ fl_draw() [1/5]

void fl_draw	(	const char *	str,
		int	x,
		int	y
	)

Draw a nul-terminated UTF-8 string starting at the given x, y location.

Text is aligned to the left and to the baseline of the font. To align to the bottom, subtract fl_descent() from y. To align to the top, subtract fl_descent() and add fl_height(). This version of fl_draw provides direct access to the text drawing function of the underlying OS. It does not apply any special handling to control characters.

◆ fl_draw() [2/5]

void fl_draw	(	const char *	str,
		int	x,
		int	y,
		int	w,
		int	h,
		Fl_Align	align,
		Fl_Image *	img = `0`,
		int	draw_symbols = `1`,
		int	spacing = `0`
	)

Fancy string drawing function which is used to draw all the labels.

The string is formatted and aligned inside the passed box. Handles '\t' and '\n', expands all other control characters to '^X', and aligns inside or against the edges of the box. See Fl_Widget::align() for values of align. The value FL_ALIGN_INSIDE is ignored, as this function always prints inside the box. If img is provided and is not NULL, the image is drawn above or below the text as specified by the align value. The draw_symbols argument specifies whether or not to look for symbol names starting with the '@' character'

Parameters

[in]	str	UTF-8 string, can start and end with an '@sym' symbol, can contain '\n'
[in]	x,y,w,h	bounding box
[in]	align	label and image alignment in bounding box
[in]	img	pointer to image
[in]	draw_symbols	if true, interprete leading and trailing '@sym' as graphical symbols
[in]	spacing	spacing between text and image

◆ fl_draw() [3/5]

void fl_draw	(	const char *	str,
		int	x,
		int	y,
		int	w,
		int	h,
		Fl_Align	align,
		void()(const char , int, int, int)	callthis,
		Fl_Image *	img = `0`,
		int	draw_symbols = `1`,
		int	spacing = `0`
	)

The same as fl_draw(const char*,int,int,int,int,Fl_Align,Fl_Image*,int) with the addition of the callthis parameter, which is a pointer to a text drawing function such as fl_draw(const char*, int, int, int) to do the real work.

Parameters

[in]	str	UTF-8 string, can start and end with an '@sym' symbol, can contain '\n'
[in]	x,y,w,h	bounding box
[in]	align	label and image alignment in bounding box
[in]	callthis	pointer to text drawing function
[in]	img	pointer to image
[in]	draw_symbols	if true, interprete leading and trailing '@sym' as graphical symbols
[in]	spacing	spacing between text and image

◆ fl_draw() [4/5]

void fl_draw	(	int	angle,
		const char *	str,
		int	n,
		int	x,
		int	y
	)

inline

Draw at the given x, y location a UTF-8 string of length n bytes rotating angle degrees counter-clockwise.

Note: When using X11 (Unix, Linux, Cygwin et al.) this needs Xft to work. Under plain X11 (w/o Xft) rotated text is not supported by FLTK. A warning will be issued to stderr at runtime (only once) if you use this method with an angle other than 0.

◆ fl_draw() [5/5]

void fl_draw	(	int	angle,
		const char *	str,
		int	x,
		int	y
	)

Draw a nul-terminated UTF-8 string starting at the given x, y location and rotating angle degrees counter-clockwise.

This version of fl_draw provides direct access to the text drawing function of the underlying OS and is supported by all fltk platforms except X11 without Xft.

◆ fl_draw_arrow()

void fl_draw_arrow	(	Fl_Rect	r,
		Fl_Arrow_Type	t,
		Fl_Orientation	o,
		Fl_Color	col
	)

Draw an "arrow like" GUI element for the selected scheme.

In the future this function should be integrated in Fl_Scheme as a virtual method, i.e. it would call a method like ...

Fl_Scheme::current()->draw_arrow(r, t, o, col);

Parameters

[in]	r	bounding box
[in]	t	arrow type
[in]	o	orientation
[in]	col	arrow color

Since: 1.4.0

◆ fl_draw_box()

void fl_draw_box	(	Fl_Boxtype	t,
		int	x,
		int	y,
		int	w,
		int	h,
		Fl_Color	c
	)

Draws a box using given type, position, size and color.

Parameters

[in]	t	box type
[in]	x,y,w,h	position and size
[in]	c	color

◆ fl_draw_box_focus()

void fl_draw_box_focus	(	Fl_Boxtype	bt,
		int	x,
		int	y,
		int	w,
		int	h,
		Fl_Color	fg,
		Fl_Color	bg
	)

Draws the focus rectangle inside a box using given type, position, size and color.

Boxes can set their own focus drawing callback. The focus frame does not need to be a rectangle at all, but should fit inside the shape of the box.

Parameters

[in]	bt	box type
[in]	x,y,w,h	position and size
[in]	fg,bg	foreground and background color

◆ fl_draw_check()

void fl_draw_check	(	Fl_Rect	bb,
		Fl_Color	col
	)

Draw a check mark inside the given bounding box.

The check mark is allowed to fill the entire box but the algorithm used makes sure that a 1-pixel border is kept free if the box is large enough. You need to calculate margins for box borders etc. yourself.

The check mark size is limited (minimum and maximum size) and the check mark is always centered in the given box.

Note: If the box is too small (bad GUI design) the check mark will be drawn over the box borders. This is intentional for better user experience. Otherwise users might not be able to recognize if a box is checked.

The size limits are implementation details and may be changed at any time.

Parameters

[in]	bb	rectangle that defines the bounding box
[in]	col	Fl_Color to draw the check mark

Since: 1.4.0

◆ fl_draw_circle()

void fl_draw_circle	(	int	x,
		int	y,
		int	d,
		Fl_Color	color
	)

Draw a potentially small, filled circle using a given color.

This function draws a filled circle bounded by rectangle (x, y, d, d) using color color

This function is the same as fl_pie(x, y, d, d, 0, 360) except with some systems that don't draw small circles well. In that situation, the circle diameter d is converted from FLTK units to pixels and this function approximates a filled circle by drawing several filled rectangles if the converted diameter is ≤ 6 pixels.

The current drawing color fl_color() is preserved across the call.

Parameters

[in]	x,y	coordinates of top left of the bounding box
[in]	d	diameter == width and height of the bounding box in FLTK units
[in]	color	the color used to draw the circle

Since: 1.4.0

◆ fl_draw_image() [1/2]

void fl_draw_image	(	const uchar *	buf,
		int	X,
		int	Y,
		int	W,
		int	H,
		int	D = `3`,
		int	L = `0`
	)

inline

Draw an 8-bit per color RGB or luminance image.

Parameters

[in]	buf	points at the "r" data of the top-left pixel. Color data must be in `r,g,b` order. Luminance data is only one `gray` byte.
[in]	X,Y	position where to put top-left corner of image
[in]	W,H	size of the image
[in]	D	delta to add to the pointer between pixels. It may be any value greater than or equal to 1, or it can be negative to flip the image horizontally
[in]	L	delta to add to the pointer between lines (if 0 is passed it uses `W` * `D`), and may be larger than `W` * `D` to crop data, or negative to flip the image vertically

It is highly recommended that you put the following code before the first show() of any window in your program to get rid of the dithering if possible:

Fl::visual(FL_RGB);

Fl::visual

static int visual(int)

Selects a visual so that your graphics are drawn correctly.

Definition: Fl_visual.cxx:49

Gray scale (1-channel) images may be drawn. This is done if abs(D) is less than 3, or by calling fl_draw_image_mono(). Only one 8-bit sample is used for each pixel, and on screens with different numbers of bits for red, green, and blue only gray colors are used. Setting D greater than 1 will let you display one channel of a color image.

Note:: The X version does not support all possible visuals. If FLTK cannot draw the image in the current visual it will abort. FLTK supports any visual of 8 bits or less, and all common TrueColor visuals up to 32 bits.

◆ fl_draw_image() [2/2]

void fl_draw_image	(	Fl_Draw_Image_Cb	cb,
		void *	data,
		int	X,
		int	Y,
		int	W,
		int	H,
		int	D = `3`
	)

inline

Draw an image using a callback function to generate image data.

You can generate the image as it is being drawn, or do arbitrary decompression of stored data, provided it can be decompressed to individual scan lines.

Parameters

[in]	cb	callback function to generate scan line data
[in]	data	user data passed to callback function
[in]	X,Y	screen position of top left pixel
[in]	W,H	image width and height
[in]	D	data size per pixel in bytes (must be greater than 0)

See also: fl_draw_image(const uchar* buf, int X, int Y, int W, int H, int D, int L)

The callback function cb is called with the void* data user data pointer to allow access to a structure of information about the image, and the x, y, and w of the scan line desired from the image. 0,0 is the upper-left corner of the image, not x, y. A pointer to a buffer to put the data into is passed. You must copy w pixels from scanline y, starting at pixel x, to this buffer.

Due to cropping, less than the whole image may be requested. So x may be greater than zero, the first y may be greater than zero, and w may be less than W. The buffer is long enough to store the entire W * D pixels, this is for convenience with some decompression schemes where you must decompress the entire line at once: decompress it into the buffer, and then if x is not zero, copy the data over so the x'th pixel is at the start of the buffer.

You can assume the y's will be consecutive, except the first one may be greater than zero.

If D is 4 or more, you must fill in the unused bytes with zero.

◆ fl_draw_image_mono() [1/2]

void fl_draw_image_mono	(	const uchar *	buf,
		int	X,
		int	Y,
		int	W,
		int	H,
		int	D = `1`,
		int	L = `0`
	)

inline

Draw a gray-scale (1 channel) image.

See also: fl_draw_image(const uchar* buf, int X,int Y,int W,int H, int D, int L)

◆ fl_draw_image_mono() [2/2]

void fl_draw_image_mono	(	Fl_Draw_Image_Cb	cb,
		void *	data,
		int	X,
		int	Y,
		int	W,
		int	H,
		int	D = `1`
	)

inline

Draw a gray-scale image using a callback function to generate image data.

See also: fl_draw_image(Fl_Draw_Image_Cb cb, void* data, int X,int Y,int W,int H, int D)

◆ fl_draw_pixmap() [1/2]

int fl_draw_pixmap	(	char const	data,
		int	x,
		int	y,
		Fl_Color	bg = `FL_GRAY`
	)

inline

Draw XPM image data, with the top-left corner at the given position.

See also: fl_draw_pixmap(const char* const* data, int x, int y, Fl_Color bg)

◆ fl_draw_pixmap() [2/2]

int fl_draw_pixmap	(	const char const	data,
		int	x,
		int	y,
		Fl_Color	bg = `FL_GRAY`
	)

Draw XPM image data, with the top-left corner at the given position.

The image is dithered on 8-bit displays so you won't lose color space for programs displaying both images and pixmaps.

Parameters

[in]	data	pointer to XPM image data
[in]	x,y	position of top-left corner
[in]	bg	background color

Returns: 0 if there was any error decoding the XPM data.

◆ fl_draw_radio()

void fl_draw_radio	(	int	x,
		int	y,
		int	d,
		Fl_Color	color
	)

Draw a round check mark (circle) of a radio button.

This draws only the round "radio button mark", it does not draw the (also typically round) box of the radio button.

Call this only if the radio button is ON.

This method draws a scheme specific "circle" with a particular light effect if the scheme is gtk+. For all other schemes this function draws a simple, small circle.

The color must be chosen by the caller so it has enough contrast with the background.

The bounding box of the circle is the rectangle (x, y, d, d).

The current drawing color fl_color() is preserved across the call.

Parameters

[in]	x,y	coordinates of top left of the bounding box
[in]	d	diameter == width and height of the bounding box in FLTK units
[in]	color	the base color used to draw the circle

Since: 1.4.0

◆ fl_draw_symbol()

int fl_draw_symbol	(	const char *	label,
		int	x,
		int	y,
		int	w,
		int	h,
		Fl_Color	col
	)

Draw the named symbol in the given rectangle using the given color.

Parameters

[in]	label	name of symbol
[in]	x,y	position of symbol
[in]	w,h	size of symbol
[in]	col	color of symbox

Returns: 1 on success, 0 on failure

◆ fl_expand_text()

const char * fl_expand_text	(	const char *	from,
		char *	buf,
		int	maxbuf,
		double	maxw,
		int &	n,
		double &	width,
		int	wrap,
		int	draw_symbols
	)

Copy from to buf, replacing control characters with ^X.

Stop at a newline or if maxbuf characters written to buffer. Also word-wrap if width exceeds maxw. Returns a pointer to the start of the next line of characters. Sets n to the number of characters put into the buffer. Sets width to the width of the string in the current font.

Parameters

[in]	from	input text, can contain ' ' and single or double '@' characters
[out]	buf	buffer for the output text segment
[in]	maxbuf	size of the buffer, or 0 to use the internal buffer allocated in this function
[in]	maxw	maximum width in pixels of the output text
[out]	n	number of characters in the output text segment
[out]	width	actual width in pixels of the output text
[in]	wrap	if true, wrap at maxw, else wrap at newlines
[in]	draw_symbols	if true, double '@' characters are escaped into a single '@'

Returns: pointer to the next character in the input text

◆ fl_focus_rect()

void fl_focus_rect	(	int	x,
		int	y,
		int	w,
		int	h
	)

inline

Draw a dotted rectangle, used to indicate keyboard focus on a widget.

This method draws the rectangle in the current color and independent of the Fl::visible_focus() option. You may need to set the current color with fl_color() before you call this.

◆ fl_frame()

void fl_frame	(	const char *	s,
		int	x,
		int	y,
		int	w,
		int	h
	)

Draws a series of line segments around the given box.

The string s must contain groups of 4 letters which specify one of 24 standard grayscale values, where 'A' is black and 'X' is white. The order of each set of 4 characters is: top, left, bottom, right. The result of calling fl_frame() with a string that is not a multiple of 4 characters in length is undefined. The only difference between this function and fl_frame2() is the order of the line segments.

Parameters

[in]	s	sets of 4 grayscale values in top, left, bottom, right order
[in]	x,y,w,h	position and size

◆ fl_frame2()

void fl_frame2	(	const char *	s,
		int	x,
		int	y,
		int	w,
		int	h
	)

Draws a series of line segments around the given box.

The string s must contain groups of 4 letters which specify one of 24 standard grayscale values, where 'A' is black and 'X' is white. The order of each set of 4 characters is: bottom, right, top, left. The result of calling fl_frame2() with a string that is not a multiple of 4 characters in length is undefined. The only difference between this function and fl_frame() is the order of the line segments.

Parameters

[in]	s	sets of 4 grayscale values in bottom, right, top, left order
[in]	x,y,w,h	position and size

◆ fl_gap()

void fl_gap ( )

inline

Separate loops of the path.

It is unnecessary but harmless to call fl_gap() before the first vertex, after the last vertex, or several times in a row.

◆ fl_line_style()

void fl_line_style	(	int	style,
		int	width = `0`,
		char *	dashes = `0`
	)

inline

Set how to draw lines (the "pen").

If you change this it is your responsibility to set it back to the default using fl_line_style(0).

fl_line_style() styles

Parameters

[in]	style	A bitmask which is a bitwise-OR of Line Styles, a cap style, and a join style. If you don't specify a dash type you will get a solid line. If you don't specify a cap or join type you will get a system-defined default of whatever value is fastest.
[in]	width	The thickness of the lines in pixels. Zero results in the system defined default, which on both X and Windows is somewhat different and nicer than 1.
[in]	dashes	A pointer to an array of dash lengths, measured in pixels. The first location is how long to draw a solid portion, the next is how long to draw the gap, then the solid, etc. It is terminated with a zero-length entry. A `NULL` pointer or a zero-length array results in a solid line. Odd array sizes are not supported and result in undefined behavior.

Note: Because of how line styles are implemented on Win32 systems, you must set the line style after setting the drawing color. If you set the color after the line style you will lose the line style settings.; The dashes array does not work under the (unsupported!) operating systems Windows 95, 98 or Me, since those operating systems do not support complex line styles.

◆ fl_load_matrix()

void fl_load_matrix	(	double	a,
		double	b,
		double	c,
		double	d,
		double	x,
		double	y
	)

inline

Set the current transformation matrix.

Parameters

[in] a,b,c,d,x,y transformation matrix elements

◆ fl_measure()

void fl_measure	(	const char *	str,
		int &	w,
		int &	h,
		int	draw_symbols
	)

Measure how wide and tall the string will be when printed by the fl_draw() function with align parameter.

If the incoming w is non-zero it will wrap to that width.

The current font is used to do the width/height calculations, so unless its value is known at the time fl_measure() is called, it is advised to first set the current font with fl_font(). With event-driven GUI programming you can never be sure which widget was exposed and redrawn last, nor which font it used. If you have not called fl_font() explicitly in your own code, the width and height may be set to unexpected values, even zero!

Note: In the general use case, it's a common error to forget to set w to 0 before calling fl_measure() when wrap behavior isn't needed.

Parameters

[in]	str	nul-terminated string
[in,out]	w	call with w=0, or with the prefered width for word wrapping, returns with the width of the string in current font
[out]	h	height of string in current font
[in]	draw_symbols	non-zero to enable @symbol handling [default=1]

// Example: Common use case for fl_measure()
const char *s = "This is a test";
int wi=0, hi=0;              // initialize to zero before calling fl_measure()
fl_font(FL_HELVETICA, 14);   // set current font face/size to be used for measuring
fl_measure(s, wi, hi);       // returns pixel width/height of string in current font

◆ fl_measure_pixmap() [1/2]

int fl_measure_pixmap	(	char const	data,
		int &	w,
		int &	h
	)

Get the dimensions of a pixmap.

An XPM image contains the dimensions in its data. This function returns the width and height.

Parameters

[in]	data	pointer to XPM image data.
[out]	w,h	width and height of image

Returns: non-zero if the dimensions were parsed OK; 0 if there were any problems

◆ fl_measure_pixmap() [2/2]

int fl_measure_pixmap	(	const char const	cdata,
		int &	w,
		int &	h
	)

Get the dimensions of a pixmap.

See also: fl_measure_pixmap(char* const* data, int &w, int &h)

◆ fl_mult_matrix()

void fl_mult_matrix	(	double	a,
		double	b,
		double	c,
		double	d,
		double	x,
		double	y
	)

inline

Concatenate another transformation onto the current one.

Parameters

[in] a,b,c,d,x,y transformation matrix elements such that X' = aX + cY + x and Y' = bX +dY + y

◆ fl_not_clipped()

int fl_not_clipped	(	int	x,
		int	y,
		int	w,
		int	h
	)

inline

Does the rectangle intersect the current clip region?

Parameters

[in] x,y,w,h position and size of rectangle

Returns: non-zero if any of the rectangle intersects the current clip region. If this returns 0 you don't have to draw the object.

Note: Under X this returns 2 if the rectangle is partially clipped and 1 if it is entirely inside the clip region.

See also: fl_clip_box()

◆ fl_old_shortcut()

unsigned int fl_old_shortcut ( const char * s )

Emulation of XForms named shortcuts.

Converts ASCII shortcut specifications (eg. "^c") into the FLTK integer equivalent (eg. FL_CTRL+'c')

These ASCII characters are used to specify the various keyboard modifier keys:

 # - Alt
 + - Shift
 ^ - Control
 ! - Meta
 @ - Command (Ctrl on linux/win, Meta on OSX)

These special characters can be combined to form chords of modifier keys. (See 'Remarks' below)

After the optional modifier key prefixes listed above, one can either specify a single keyboard character to use as the shortcut, or a numeric sequence in hex, decimal or octal.

Examples:

 "c"      -- Uses 'c' as the shortcut
 "#^c"    -- Same as FL_ALT|FL_CTRL|'c'
 "#^!c"   -- Same as FL_ALT|FL_CTRL|FL_META|'c'
 "@c"     -- Same as FL_COMMAND|'c' (see FL_COMMAND for platform specific behavior)
 "0x63"   -- Same as "c" (hex 63=='c')
 "99"     -- Same as "c" (dec 99=='c')
 "0143"   -- Same as "c" (octal 0143=='c')
 "^0x63"  -- Same as (FL_CTRL|'c'), or (FL_CTRL|0x63)
 "^99"    -- Same as (FL_CTRL|'c'), or (FL_CTRL|99)
 "^0143"  -- Same as (FL_CTRL|'c'), or (FL_CTRL|0143)

Remarks

Due to XForms legacy, there are some odd things to consider when using the modifier characters.

(1) You can use the special modifier keys for chords only if the modifiers are provided in this order: #, +, ^, !, @. Other ordering can yield undefined results.

So for instance, Ctrl-Alt-c must be specified as "#^c" (and not "^#c"), due to the above ordering rule.

(2) If you want to make a shortcut that uses one of the special modifier characters (as the character being modified), then to avoid confusion, specify the numeric equivalent, e.g.

 If you want..                    Then use..
 -----------------------------    ------------------------------
 '#' as the shortcut..            "0x23"  (instead of just "#").
 '+' as the shortcut..            "0x2b"  (instead of just "+").
 '^' as the shortcut..            "0x5e"  (instead of just "^").
 Alt-+ as the shortcut..          "#0x2b" (instead of "#+").
 Alt-^ as the shortcut..          "#0x5e" (instead of "#^").
 ..etc..

As a general rule that's easy to remember, unless the shortcut key to be modified is a single alpha-numeric character [A-Z,a-z,0-9), it's probably best to use the numeric equivalents.

Don't fix these silly legacy issues in a future release. Nobody is using this anymore.

◆ fl_overlay_clear()

void fl_overlay_clear ( )

Erase a selection rectangle without drawing a new one.

See also: fl_overlay_rect(int x, int y, int w, int h)

◆ fl_overlay_rect()

void fl_overlay_rect	(	int	x,
		int	y,
		int	w,
		int	h
	)

Draw a transient dotted selection rectangle.

This function saves the current screen content and then draws a dotted selection rectangle into the front screen buffer. If another selection rectangle was drawn earlier, the previous screen graphics are restored first.

To clear the selection rectangle, call fl_overlay_clear().

The typical (and only) use for this function is to draw a selection rectangle during a mouse drag event sequence without having to redraw the entire content of the widget.

Your event handle should look similar to this (also see test/mandelbrot.cxx):

int MyWidget::handle(int event) {
  static int ix, iy;
  switch (event) {
    case FL_PUSH:
      ix = Fl::event_x(); iy = Fl::event_y();
      return 1;
    case FL_DRAG:
      this->make_current();
      fl_overlay_rect(ix, iy, ix-Fl::event_x(), iy-Fl::event_y());
      return 1;
    case FL_RELEASE:
      this->make_current();
      fl_overlay_clear();
      // select the element under the rectangle
      return 1;
  }
  return MySuperWidget::handle(event);
}

Note: Between drawing an overlay rect and clearing it, the content of the widget must not change.; fl_overlay_rect() and fl_overlay_clear() should be called when the actual event occurs, and not within MyWidget::draw().; fl_overlay_rect() and fl_overlay_clear() should not be mixed with Fl_Overlay_Window. Fl_Overlay_Window provides an entirely different way of drawing selection outlines and is not limited to rectangles.

Parameters

x,y,w,h position and size of the overlay rectangle.

See also: fl_overlay_clear()

◆ fl_override_scale()

float fl_override_scale ( )

Removes any GUI scaling factor in subsequent drawing operations.

This must be matched by a later call to fl_restore_scale(). This function can be used to transiently perform drawing operations that are not rescaled by the current value of the GUI scaling factor. The resulting drawing context has no clipping region.

Returns: The GUI scaling factor value that was in place when the function started.

◆ fl_pie()

void fl_pie	(	int	x,
		int	y,
		int	w,
		int	h,
		double	a1,
		double	a2
	)

inline

Draw filled ellipse sections using integer coordinates.

Like fl_arc(), but fl_pie() draws a filled-in pie slice. This slice may extend outside the line drawn by fl_arc(); to avoid this use w - 1 and h - 1.

Parameters

[in]	x,y,w,h	bounding box of complete circle
[in]	a1,a2	start and end angles of arc measured in degrees counter-clockwise from 3 o'clock. `a2` must be greater than or equal to `a1`.

fl_pie() and fl_arc()

◆ fl_polygon()

void fl_polygon	(	int	x,
		int	y,
		int	x1,
		int	y1,
		int	x2,
		int	y2,
		int	x3,
		int	y3
	)

inline

Fill a 4-sided polygon.

The polygon must be convex.

◆ fl_pop_clip()

void fl_pop_clip ( )

inline

Restore the previous clip region.

You must call fl_pop_clip() once for every time you call fl_push_clip(). Unpredictable results may occur if the clip stack is not empty when you return to FLTK.

◆ fl_push_clip()

void fl_push_clip	(	int	x,
		int	y,
		int	w,
		int	h
	)

inline

Intersect the current clip region with a rectangle and push this new region onto the stack.

Parameters

[in] x,y,w,h position and size

◆ fl_push_matrix()

void fl_push_matrix ( )

inline

Save the current transformation matrix on the stack.

The maximum depth of the stack is 32.

◆ fl_read_image()

uchar * fl_read_image	(	uchar *	p,
		int	X,
		int	Y,
		int	w,
		int	h,
		int	alpha
	)

Reads an RGB(A) image from the current window or off-screen buffer.

Parameters

[in]	p	pixel buffer, or NULL to allocate one
[in]	X,Y	position of top-left of image to read
[in]	w,h	width and height of image to read
[in]	alpha	alpha value for image (0 for none)

Returns: pointer to pixel buffer, or NULL if allocation failed.

The p argument points to a buffer that can hold the image and must be at least w*h*3 bytes when reading RGB images, or w*h*4 bytes when reading RGBA images. If NULL, fl_read_image() will create an array of the proper size which can be freed using delete[].

The alpha parameter controls whether an alpha channel is created and the value that is placed in the alpha channel. If 0, no alpha channel is generated.

See also: fl_capture_window()

◆ fl_rect() [1/3]

void fl_rect ( Fl_Rect r )

inline

Draw a border inside the given bounding box.

This is the same as fl_rect(int x, int y, int w, int h) but with Fl_Rect r as input argument.

◆ fl_rect() [2/3]

void fl_rect	(	int	x,
		int	y,
		int	w,
		int	h
	)

inline

Draw a border inside the given bounding box.

This function is meant for quick drawing of simple boxes. The behavior is undefined for line widths that are not 1.

◆ fl_rect() [3/3]

void fl_rect	(	int	x,
		int	y,
		int	w,
		int	h,
		Fl_Color	c
	)

inline

Draw with passed color a border inside the given bounding box.

Warning: The current color is changed to c upon return.

◆ fl_rectf() [1/4]

void fl_rectf	(	Fl_Rect	bb,
		uchar	r,
		uchar	g,
		uchar	b
	)

inline

Color a rectangle with "exactly" the passed r,g,b color.

This is the same as fl_rectf(int x, int y, int w, int h, uchar r, uchar g, uchar b) but with Fl_Rect bb (bounding box) as argument instead of (x, y, w, h).

See also: fl_rectf(int x, int y, int w, int h, uchar r, uchar g, uchar b)

◆ fl_rectf() [2/4]

void fl_rectf	(	Fl_Rect	r,
		Fl_Color	c
	)

inline

Color with passed color a rectangle that exactly fills the given bounding box.

Warning: The current color is changed to c upon return.

◆ fl_rectf() [3/4]

void fl_rectf	(	int	x,
		int	y,
		int	w,
		int	h,
		Fl_Color	c
	)

inline

Color with passed color a rectangle that exactly fills the given bounding box.

Warning: The current color is changed to c upon return.

◆ fl_rectf() [4/4]

void fl_rectf	(	int	x,
		int	y,
		int	w,
		int	h,
		uchar	r,
		uchar	g,
		uchar	b
	)

inline

Color a rectangle with "exactly" the passed r,g,b color.

On screens with less than 24 bits of color this is done by drawing a solid-colored block using fl_draw_image() so that the correct color shade is produced. On other screens, the current color is changed to fl_color(r,g,b) upon return.

◆ fl_rescale_offscreen()

void fl_rescale_offscreen ( Fl_Offscreen & ctx )

Adapts an offscreen buffer to a changed value of the scale factor.

The ctx argument must have been created by fl_create_offscreen() and the calling context must not be between fl_begin_offscreen() and fl_end_offscreen(). The graphical content of the offscreen is preserved. The current scale factor value is given by Fl_Graphics_Driver::default_driver().scale().

Version: 1.4

◆ fl_reset_spot()

void fl_reset_spot ( void )

Resets marked text.

In many languages, typing a character can involve multiple keystrokes. For example, the Ä can be composed of two dots (¨) on top of the character, followed by the letter A (on a Mac with U.S. keyboard, you'd type Alt-U, Shift-A. To inform the user that the dots may be followed by another character, the ¨ is underlined).

Call this function if character composition needs to be aborted for some reason. One such example would be the text input widget losing focus.

◆ fl_restore_scale()

void fl_restore_scale ( float s )

Restores the GUI scaling factor and the clipping region in subsequent drawing operations.

Parameters

s	Value returned by a previous call to fl_override_scale().

◆ fl_rotate()

void fl_rotate ( double d )

inline

Concatenate rotation transformation onto the current one.

Parameters

[in] d - rotation angle, counter-clockwise in degrees (not radians)

◆ fl_rounded_rect()

void fl_rounded_rect	(	int	x,
		int	y,
		int	w,
		int	h,
		int	r
	)

inline

Draw a rounded border inside the given bounding box.

The radius code is optimized for speed and works best for values between 5 and 15 units.

◆ fl_rounded_rectf()

void fl_rounded_rectf	(	int	x,
		int	y,
		int	w,
		int	h,
		int	r
	)

inline

Color with current color a rounded rectangle that exactly fills the given bounding box.

The radius code is optimized for speed and works best for values between 5 and 15 units.

◆ fl_scale() [1/2]

void fl_scale ( double x )

inline

Concatenate scaling transformation onto the current one.

Parameters

[in] x scale factor in both x-direction and y-direction

◆ fl_scale() [2/2]

void fl_scale	(	double	x,
		double	y
	)

inline

Concatenate scaling transformation onto the current one.

Parameters

[in] x,y scale factors in x-direction and y-direction

◆ fl_scroll()

void fl_scroll	(	int	X,
		int	Y,
		int	W,
		int	H,
		int	dx,
		int	dy,
		void()(void , int, int, int, int)	draw_area,
		void *	data
	)

Scroll a rectangle and draw the newly exposed portions.

Parameters

[in]	X,Y	position of top-left of rectangle
[in]	W,H	size of rectangle
[in]	dx,dy	pixel offsets for shifting rectangle
[in]	draw_area	callback function to draw rectangular areas
[in]	data	pointer to user data for callback The contents of the rectangular area is first shifted by `dx` and `dy` pixels. The `draw_area` callback is then called for every newly exposed rectangular area.

◆ fl_set_spot()

void fl_set_spot	(	int	font,
		int	size,
		int	X,
		int	Y,
		int	W,
		int	H,
		Fl_Window *	win = `0`
	)

Inform text input methods about the current text insertion cursor.

Parameters

font	Font currently in use in text input.
size	Size of the current font.
X,Y	Position of the bottom of the current text insertion cursor.
W,H	Width and height of the current text insertion cursor.
win	Points to the Fl_Window object containing the current text widget, or NULL.

◆ fl_set_status()

void fl_set_status	(	int	X,
		int	Y,
		int	W,
		int	H
	)

Related to text input methods under X11.

This function is presently used only by the utf8 test application and only for the X11 platform. This function is apparently not indispensable for text input to work correctly as suggested by other apps that don't use it (e.g., editor).

◆ fl_shortcut_label() [1/2]

const char * fl_shortcut_label ( unsigned int shortcut )

Get a human-readable string from a shortcut value.

Unparse a shortcut value as used by Fl_Button or Fl_Menu_Item into a human-readable string like "Alt+N". This only works if the shortcut is a character key or a numbered function key. If the shortcut is zero then an empty string is returned. The return value points at a static buffer that is overwritten with each call.

Since: FLTK 1.3.4 modifier key names can be localized, but key names can not yet be localized. This may be added to a future FLTK version.

Modifier key names (human-readable shortcut names) can be defined with the following global const char * pointer variables:

fl_local_ctrl => name of FL_CTRL
fl_local_alt => name of FL_ALT
fl_local_shift => name of FL_SHIFT
fl_local_meta => name of FL_META

fl_local_ctrl = "Strg"; // German for "Ctrl"

fl_local_shift = "Umschalt"; // German for "Shift"

fl_local_shift

const char * fl_local_shift

string pointer used in shortcuts, you can change it to another language

Definition: Fl.cxx:2388

fl_local_ctrl

const char * fl_local_ctrl

string pointer used in shortcuts, you can change it to another language

Definition: Fl.cxx:2391

Note: Due to random static initialization order this should always be done from code in main() or called by main() as opposed to static initialization since the default strings in the FLTK library are set by static initializers. Otherwise this might result in the wrong order so FLTK's internal initialization overwrites your strings.

The shortcut name will be constructed by adding all modifier names in the order defined above plus the name of the key. A '+' character is added to each modifier name unless it has a trailing '\' or a trailing '+'.

Example:

Ctrl+Alt+Shift+Meta+F12

The default values for modifier key names are as given above for all platforms except macOS. macOS uses graphical characters that represent the typical macOS modifier names in menus, e.g. cloverleaf, saucepan, etc. You may, however, redefine macOS modifier names as well.

Parameters

[in] shortcut the integer value containing the ASCII character or extended keystroke plus modifiers

Returns: a pointer to a static buffer containing human readable text for the shortcut

◆ fl_shortcut_label() [2/2]

const char * fl_shortcut_label	(	unsigned int	shortcut,
		const char **	eom
	)

Get a human-readable string from a shortcut value.

Parameters

[in]	shortcut	the integer value containing the ASCII character or extended keystroke plus modifiers
[in]	eom	if this pointer is set, it will receive a pointer to the end of the modifier text

Returns: a pointer to a static buffer containing human readable text for the shortcut

See also: fl_shortcut_label(unsigned int shortcut)

◆ fl_transform_dx()

double fl_transform_dx	(	double	x,
		double	y
	)

inline

Transform distance using current transformation matrix.

Parameters

[in] x,y coordinate

◆ fl_transform_dy()

double fl_transform_dy	(	double	x,
		double	y
	)

inline

Transform distance using current transformation matrix.

Parameters

[in] x,y coordinate

◆ fl_transform_x()

double fl_transform_x	(	double	x,
		double	y
	)

inline

Transform coordinate using the current transformation matrix.

Parameters

[in] x,y coordinate

◆ fl_transform_y()

double fl_transform_y	(	double	x,
		double	y
	)

inline

Transform coordinate using the current transformation matrix.

Parameters

[in] x,y coordinate

◆ fl_transformed_vertex()

void fl_transformed_vertex	(	double	xf,
		double	yf
	)

inline

Add coordinate pair to the vertex list without further transformations.

Parameters

[in] xf,yf transformed coordinate

◆ fl_translate()

void fl_translate	(	double	x,
		double	y
	)

inline

Concatenate translation transformation onto the current one.

Parameters

[in] x,y translation factor in x-direction and y-direction

◆ fl_vertex()

void fl_vertex	(	double	x,
		double	y
	)

inline

Add a single vertex to the current path.

Parameters

[in] x,y coordinate

Enumerations

Functions

Detailed Description

Enumeration Type Documentation

◆ anonymous enum

Function Documentation

◆ fl_add_symbol()

◆ fl_antialias()

◆ fl_arc() [1/2]

◆ fl_arc() [2/2]

◆ fl_begin_complex_polygon()

◆ fl_begin_offscreen()

◆ fl_begin_points()

◆ fl_can_do_alpha_blending()

◆ fl_capture_window()

◆ fl_circle()

◆ fl_clip()

◆ fl_clip_box()

◆ fl_clip_region() [1/2]

◆ fl_clip_region() [2/2]

◆ fl_copy_offscreen()

◆ fl_create_offscreen()

◆ fl_cursor()

◆ fl_curve()

◆ fl_delete_offscreen()

◆ fl_draw() [1/5]

◆ fl_draw() [2/5]

◆ fl_draw() [3/5]

◆ fl_draw() [4/5]

◆ fl_draw() [5/5]

◆ fl_draw_arrow()

◆ fl_draw_box()

◆ fl_draw_box_focus()

◆ fl_draw_check()

◆ fl_draw_circle()

◆ fl_draw_image() [1/2]

◆ fl_draw_image() [2/2]

◆ fl_draw_image_mono() [1/2]

◆ fl_draw_image_mono() [2/2]

◆ fl_draw_pixmap() [1/2]

◆ fl_draw_pixmap() [2/2]

◆ fl_draw_radio()

◆ fl_draw_symbol()

◆ fl_expand_text()

◆ fl_focus_rect()

◆ fl_frame()

◆ fl_frame2()

◆ fl_gap()

◆ fl_line_style()

◆ fl_load_matrix()

◆ fl_measure()

◆ fl_measure_pixmap() [1/2]

◆ fl_measure_pixmap() [2/2]

◆ fl_mult_matrix()

◆ fl_not_clipped()

◆ fl_old_shortcut()

◆ fl_overlay_clear()

◆ fl_overlay_rect()

◆ fl_override_scale()

◆ fl_pie()

◆ fl_polygon()

◆ fl_pop_clip()

◆ fl_push_clip()

◆ fl_push_matrix()

◆ fl_read_image()

◆ fl_rect() [1/3]

◆ fl_rect() [2/3]

◆ fl_rect() [3/3]

◆ fl_rectf() [1/4]

◆ fl_rectf() [2/4]

◆ fl_rectf() [3/4]

◆ fl_rectf() [4/4]

◆ fl_rescale_offscreen()

◆ fl_reset_spot()

◆ fl_restore_scale()

◆ fl_rotate()

◆ fl_rounded_rect()

◆ fl_rounded_rectf()

◆ fl_scale() [1/2]

◆ fl_scale() [2/2]