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Cairo: introduce Fl::cairo_flush() in FLTK API

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Flushing the Cairo context is necessary on Windows to make Cairo
drawings appear on the device (screen). This new method makes it easy
for user code to do this correctly after using Cairo drawings.

- add Fl::cairo_flush(cairo_t *)
- document Fl::cairo_flush(cairo_t *)
- reformat Cairo doxygen docs and code (partially)
- use the new method in Fl_Cairo_Window
- use the new method in test/cairo_test.cxx
- other minor (text) changes in test/cairo_test.cxx
- add test/cairo_test to the demo menu (test/demo.menu)
This commit is contained in:
Albrecht Schlosser 2023-03-14 18:46:56 +01:00
parent 0eb6a0e193
commit 0f41797b7a
5 changed files with 94 additions and 42 deletions
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110
FL/Fl.H
View File

@ -1399,42 +1399,96 @@ public:
*/
public:
// Cairo support API
static cairo_t * cairo_make_current(Fl_Window* w);
/** when FLTK_HAVE_CAIRO is defined and cairo_autolink_context() is true,
any current window dc is linked to a current cairo context.
This is not the default, because it may not be necessary
to add cairo support to all fltk supported windows.
When you wish to associate a cairo context in this mode,
you need to call explicitly in your draw() overridden method,
Fl::cairo_make_current(Fl_Window*). This will create a cairo context
but only for this Window.
Still in custom cairo application it is possible to handle
completely this process automatically by setting \p alink to true.
In this last case, you don't need anymore to call Fl::cairo_make_current().
You can use Fl::cairo_cc() to get the current cairo context anytime.
\note Only available when configure has the --enable-cairo option
static cairo_t *cairo_make_current(Fl_Window *w);
/** When FLTK_HAVE_CAIRO is defined and cairo_autolink_context() is true,
any current window dc is linked to a current Cairo context.
This is not the default, because it may not be necessary
to add Cairo support to all fltk supported windows.
When you wish to associate a Cairo context in this mode,
you need to call explicitly in your draw() overridden method,
Fl::cairo_make_current(Fl_Window*). This will create a Cairo context
only for this Window.
Still in custom Cairo application it is possible to handle
completely this process automatically by setting \p alink to true.
In this last case, you don't need anymore to call Fl::cairo_make_current().
You can use Fl::cairo_cc() to get the current Cairo context anytime.
\note Only available when configure has the --enable-cairo option
*/
static void cairo_autolink_context(bool alink) {cairo_state_.autolink(alink);}
static void cairo_autolink_context(bool alink) {
cairo_state_.autolink(alink);
}
/**
Gets the current autolink mode for cairo support.
\retval false if no cairo context autolink is made for each window.
\retval true if any fltk window is attached a cairo context when it
Gets the current autolink mode for Cairo support.
\retval false if no Cairo context autolink is made for each window.
\retval true if any fltk window is attached a Cairo context when it
is current. \see void cairo_autolink_context(bool alink)
\note Only available when configure has the --enable-cairo option
*/
static bool cairo_autolink_context() {return cairo_state_.autolink();}
/** Gets the current cairo context linked with a fltk window. */
static cairo_t * cairo_cc() { return cairo_state_.cc(); }
/** Sets the current cairo context to \p c.
Set \p own to true if you want fltk to handle this cc deletion.
\note Only available when configure has the --enable-cairo option
*/
static void cairo_cc(cairo_t * c, bool own=false){ cairo_state_.cc(c, own); }
static bool cairo_autolink_context() {
return cairo_state_.autolink();
}
/** Gets the current Cairo context linked with a fltk window. */
static cairo_t *cairo_cc() {
return cairo_state_.cc();
}
/** Sets the current Cairo context to \p c.
Set \p own to true if you want fltk to handle this cc deletion.
\note Only available when configure has the --enable-Cairo option
*/
static void cairo_cc(cairo_t *c, bool own=false) {
cairo_state_.cc(c, own);
}
/** Flush Cairo drawings on Cairo context \p c.
This is \b required on Windows if you use the Cairo context provided
by the "Cairo autolink" option. Call this when all your drawings on
the Cairo context are finished. This is maybe not necessary on other
platforms than Windows but it does no harm if you call it always.
You don't need to use this if you use an Fl_Cairo_Window which does
this automatically after the draw callback returns.
Code example for "Cairo autolink" mode:
In the overridden draw() method of your subclass of Fl_Window or any
widget:
\code
cairo_t *cc = Fl::cairo_cc(); // get the "autolink" Cairo context
// ... your Cairo drawings are here ...
Fl::cairo_flush(cc); // flush Cairo drawings to the device
\endcode
If you configure FLTK with \c '--enable-cairo' or CMake option
\c 'OPTION_CAIRO' (i.e. without \c '--enable-cairoext' or CMake option
\c 'OPTION_CAIROEXT') or if you don't enable the \c 'autolink' Cairo
context you may do the equivalent to use Cairo drawings in an
overridden draw() method of derived classes by using
\code
// get the Cairo context for the \c window
cairo_t *cc = Fl::cairo_make_current(window);
// ... your Cairo drawings are here ...
Fl::cairo_flush(cc); // flush Cairo drawings to the device
\endcode
\see Fl::cairo_autolink_context(bool)
\see Fl::cairo_make_current(Fl_Window*);
*/
static void cairo_flush(cairo_t *c) {
// flush Cairo drawings: necessary at least for Windows
cairo_surface_t *s = cairo_get_target(Fl::cairo_cc());
cairo_surface_flush(s);
}
private:
static cairo_t * cairo_make_current(void* gc);
static cairo_t * cairo_make_current(void* gc, int W, int H);
static cairo_t *cairo_make_current(void *gc);
static cairo_t *cairo_make_current(void *gc, int W, int H);
static Fl_Cairo_State cairo_state_;
public:
/** @} */

4
FL/Fl_Cairo.H
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@ -1,7 +1,7 @@
//
// Main Cairo header file for the Fast Light Tool Kit (FLTK).
// Main Cairo support header file for the Fast Light Tool Kit (FLTK).
//
// Copyright 1998-2022 by Bill Spitzak and others.
// Copyright 1998-2023 by Bill Spitzak and others.
//
// This library is free software. Distribution and use rights are outlined in
// the file "COPYING" which should have been included with this file. If this

3
FL/Fl_Cairo_Window.H
View File

@ -102,8 +102,7 @@ protected:
Fl::cairo_make_current(this);
draw_cb_(this, Fl::cairo_cc());
// flush Cairo drawings: necessary at least for Windows
cairo_surface_t *s = cairo_get_target(Fl::cairo_cc());
cairo_surface_flush(s);
Fl::cairo_flush(Fl::cairo_cc());
}
}

18
test/cairo_test.cxx
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@ -1,7 +1,7 @@
//
// Cairo drawing test program for the Fast Light Tool Kit (FLTK).
//
// Copyright 1998-2022 by Bill Spitzak and others.
// Copyright 1998-2023 by Bill Spitzak and others.
//
// This library is free software. Distribution and use rights are outlined in
// the file "COPYING" which should have been included with this file. If this
@ -155,15 +155,17 @@ typedef Fl_Cairo_Window cairo_using_window;
class cairo_using_window : public Fl_Double_Window {
void (*draw_with_cairo_)(cairo_using_window*, cairo_t*);
public:
cairo_using_window(int w, int h, const char *title) : Fl_Double_Window(w, h, title) {
Fl_Box *box = new Fl_Box(FL_NO_BOX, 0, 0, w, 25,
"use Cairo and the FLTK API in Fl_Double_Window");
"Cairo and FLTK API in Fl_Double_Window");
box->labelfont(FL_TIMES_BOLD);
box->labelsize(12);
box->labelcolor(FL_BLUE);
}
void draw() {
void draw() FL_OVERRIDE {
Fl_Window::draw(); // perform drawings with the FLTK API
#ifndef FLTK_HAVE_CAIROEXT
Fl::cairo_make_current(this); // announce Cairo will be used in this window
@ -172,13 +174,9 @@ public:
draw_with_cairo_(this, cc); // draw in this window using Cairo
// flush Cairo drawings: necessary at least for Windows
// see also FL/Fl_Cairo_Window.H
// FIXME: this should be simplified with an FLTK API, for instance:
// Fl::cairo_flush(cc);
cairo_surface_t *s = cairo_get_target(cc);
cairo_surface_flush(s);
Fl::cairo_flush(cc);
}
void set_draw_cb( void (*cb)(cairo_using_window*, cairo_t*)) {
draw_with_cairo_ = cb;
}
@ -196,7 +194,7 @@ int main(int argc, char **argv) {
#ifdef FLTK_HAVE_CAIROEXT
Fl::cairo_autolink_context(true);
#endif
cairo_using_window window(300, 300, "FLTK loves Cairo");
cairo_using_window window(350, 350, "FLTK loves Cairo");
window.resizable(&window);
window.color(FL_WHITE);

1
test/demo.menu
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@ -66,6 +66,7 @@
@e:Mandelbrot:mandelbrot
@e:Fractals:fractals
@e:Puzzle:glpuzzle
@e:Cairo\nSupport:cairo_test
@e:Block\nAttack!:blocks
@e:Checkers:checkers
@e:Sudoku:sudoku