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docs: Update the developer section of egl.html. 

Mainly to add a subsection about EGL_RENDER_BUFFER.
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Chia-I Wu 2010-02-05 12:44:45 +08:00
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@ -267,6 +267,41 @@ uninitialized display.</p>
resources. The drivers are responsible to the correct behavior as defined by
EGL.</p>
<h3><code>EGL_RENDER_BUFFER</code></h3>
<p>In EGL, the color buffer a context should try to render to is decided by the
binding surface. It should try to render to the front buffer if the binding
surface has <code>EGL_RENDER_BUFFER</code> set to
<code>EGL_SINGLE_BUFFER</code>; If the same context is later bound to a
surface with <code>EGL_RENDER_BUFFER</code> set to
<code>EGL_BACK_BUFFER</code>, the context should try to render to the back
buffer. However, the context is allowed to make the final decision as to which
color buffer it wants to or is able to render to.</p>
<p>For pbuffer surfaces, the render buffer is always
<code>EGL_BACK_BUFFER</code>. And for pixmap surfaces, the render buffer is
always <code>EGL_SINGLE_BUFFER</code>. Unlike window surfaces, EGL spec
requires their <code>EGL_RENDER_BUFFER</code> values to be honored. As a
result, a driver should never set <code>EGL_PIXMAP_BIT</code> or
<code>EGL_PBUFFER_BIT</code> bits of a config if the contexts created with the
config won't be able to honor the <code>EGL_RENDER_BUFFER</code> of pixmap or
pbuffer surfaces.</p>
<p>It should also be noted that pixmap and pbuffer surfaces are assumed to be
single-buffered, in that <code>eglSwapBuffers</code> has no effect on them. It
is desirable that a driver allocates a private color buffer for each pbuffer
surface created. If the window system the driver supports has native pbuffers,
or if the native pixmaps have more than one color buffers, the driver should
carefully attach the native color buffers to the EGL surfaces, re-route them if
required.</p>
<p>There is no defined behavior as to, for example, how
<code>glDrawBuffer</code> interacts with <code>EGL_RENDER_BUFFER</code>. Right
now, it is desired that the draw buffer in a client API be fixed for pixmap and
pbuffer surfaces. Therefore, the driver is responsible to guarantee that the
client API renders to the specified render buffer for pixmap and pbuffer
surfaces.</p>
<h3>TODOs</h3>
<ul>