path: root/docs
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authorChia-I Wu <>2010-02-05 12:44:45 +0800
committerChia-I Wu <>2010-02-05 12:48:49 +0800
commit1b2b08c5f3a5941151a2f4a8c5da7f214ee979e4 (patch)
treed9b9e927c6ac367bbb2a7740e72e5b05244ea809 /docs
parent5f08eff2a769e27df37fc00e46797e70a54727bb (diff)
docs: Update the developer section of egl.html.
Mainly to add a subsection about EGL_RENDER_BUFFER.
Diffstat (limited to 'docs')
1 files changed, 35 insertions, 0 deletions
diff --git a/docs/egl.html b/docs/egl.html
index cdfae044a8a..9eba402411d 100644
--- a/docs/egl.html
+++ b/docs/egl.html
@@ -267,6 +267,41 @@ uninitialized display.</p>
resources. The drivers are responsible to the correct behavior as defined by
+<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
+<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