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Added some example code to Fl_Gl_Window::draw() docs..

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git-svn-id: file:///fltk/svn/fltk/branches/branch-1.4@12235 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
This commit is contained in:
Greg Ercolano 2017-05-11 11:44:06 +00:00
parent 39b2976f88
commit 039beaf26a
1 changed files with 39 additions and 1 deletions
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40
src/Fl_Gl_Window.cxx
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@ -342,7 +342,7 @@ void Fl_Gl_Window::draw_overlay() {}
#endif // HAVE_GL
/** Draws the Fl_Gl_Window.
/** Draws the Fl_Gl_Window.
You \e \b must subclass Fl_Gl_Window and provide an implementation for
draw(). You may also provide an implementation of draw_overlay()
if you want to draw into the overlay planes. You can avoid
@ -356,6 +356,44 @@ void Fl_Gl_Window::draw_overlay() {}
If double-buffering is enabled in the window, the back and front
buffers are swapped after this function is completed.
The following pseudo-code shows how to use "if (!valid())"
to initialize the viewport:
\code
void mywindow::draw() {
if (!valid()) {
glViewport(0,0,pixel_w(),pixel_h());
glFrustum(...) or glOrtho(...)
...other initialization...
}
if (!context_valid()) {
...load textures, etc. ...
}
// clear screen
glClearColor(...);
glClear(...);
... draw your geometry here ...
}
\endcode
Actual example code to clear screen to black and draw a 2D white "X":
\code
void mywindow::draw() {
if (!valid()) {
glLoadIdentity();
glViewport(0,0,w(),h());
glOrtho(-w(),w(),-h(),h(),-1,1);
}
// Clear screen
glClear(GL_COLOR_BUFFER_BIT);
// Draw white 'X'
glColor3f(1.0, 1.0, 1.0);
glBegin(GL_LINE_STRIP); glVertex2f(w(), h()); glVertex2f(-w(),-h()); glEnd();
glBegin(GL_LINE_STRIP); glVertex2f(w(),-h()); glVertex2f(-w(), h()); glEnd();
}
\endcode
*/
void Fl_Gl_Window::draw() {
#ifdef FL_CFG_GFX_OPENGL