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Added a section on damage() for widget writers.

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git-svn-id: file:///fltk/svn/fltk/trunk@266 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
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Michael R Sweet
1999-02-01 20:38:57 +00:00
parent 3377e6e0d5
commit 44f8e8e32a
1 changed files with 22 additions and 5 deletions
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documentation/opengl.html
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@@ -17,13 +17,31 @@ include the file <TT>&lt;GL/gl.h&gt;</TT>, define some extra drawing
functions provided by FLTK, and include the <TT>&lt;windows.h&gt;</TT> header functions provided by FLTK, and include the <TT>&lt;windows.h&gt;</TT> header
file needed by WIN32 applications. </P> file needed by WIN32 applications. </P>
<H2>Making a Subclass of Fl_Gl_Window</H2> <H2>Making a Subclass of Fl_Gl_Window</H2>
To make a subclass of Fl_Gl_Window, you must provide: To make a subclass of Fl_Gl_Window, you must provide:
<UL> <UL>
<LI>A class definition. </LI> <LI>A class definition. </LI>
<LI>A <TT>draw()</TT> method. </LI> <LI>A <TT>draw()</TT> method. </LI>
<LI>A <TT>handle()</TT> method (if you need to recieve input from the <LI>A <TT>handle()</TT> method (if you need to recieve input from the
user). </LI> user). </LI>
</UL> </UL>
If your subclass provides static controls in the window, they must be
redrawn whenever the <tt>FL_DAMAGE_ALL</tt> bit is set in the value
returned by <tt>damage()</tt>. For double-buffered windows you will
need to surround the drawing code with the following code to make sure
that both buffers are redrawn:
<ul><pre>
#ifndef MESA
glDrawBuffer(GL_FRONT_AND_BACK);
#endif // !MESA
... draw stuff here ...
#ifndef MESA
glDrawBuffer(GL_BACK);
#endif // !MESA
</pre></ul>
<B>Note:</B> If you are using the Mesa graphics library, the call to
<tt>glDrawBuffer()</tt> is not required and will slow down drawing
considerably. The preprocessor instructions shown above will optimize
your code based upon the graphics library used.
<H3>Defining the Subclass</H3> <H3>Defining the Subclass</H3>
To define the subclass you just subclass the <TT>Fl_Gl_Window</TT> class: To define the subclass you just subclass the <TT>Fl_Gl_Window</TT> class:
<UL> <UL>
@@ -163,12 +181,11 @@ for maximum portability: </P>
<UL> <UL>
<LI>You must choose a default visual with <A href=functions.html#gl_visual> <LI>You must choose a default visual with <A href=functions.html#gl_visual>
<TT>Fl::gl_visual()</TT></A>. </LI> <TT>Fl::gl_visual()</TT></A>. </LI>
<LI>You cannot pass <TT>FL_DOUBLE</TT> to <TT>Fl::gl_visual()</TT>. </LI> <LI>You cannot pass <TT>FL_DOUBLE</TT> to <TT>Fl::gl_visual()</TT>.</LI>
<LI>You cannot use <TT>Fl_Double_Window</TT> or <TT>Fl_Overlay_Window</TT> <LI>You cannot use <TT>Fl_Double_Window</TT> or <TT>Fl_Overlay_Window</TT>.</LI>
. </LI>
</UL> </UL>
Do <I>not</I> call <TT>gl_start()</TT> or <TT>gl_finish()</TT> when Do <I>not</I> call <TT>gl_start()</TT> or <TT>gl_finish()</TT> when
drawing into an <TT>Fl_Gl_Window</TT>! drawing into an <TT>Fl_Gl_Window</TT>!
<H2>OpenGL Drawing Functions</H2> <H2>OpenGL Drawing Functions</H2>
FLTK provides some useful OpenGL drawing functions. They can be FLTK provides some useful OpenGL drawing functions. They can be
freely mixed with any OpenGL calls, and are defined by including <TT> freely mixed with any OpenGL calls, and are defined by including <TT>