is not available in GLX or GLX extensions.</p>
</li>
-<li><code>egl_xdri</code>
+<li><code>egl_dri2</code>
<p>This driver supports the X Window System as its window system. It functions
-as a DRI driver loader and can load DRI/DRI2/DRISW drivers. Unlike
-<code>egl_glx</code>, it has no dependency on <code>libGL</code>. It talks to
-the X server directly using DRI or DRI2 protocols. It also talks minimal GLX
-protocol for things like available visuals or fbconfigs. With direct access to
-the DRI drivers, it has the potential to support more EGL functions that are
-not possible with <code>egl_glx</code>.</p>
+as a DRI2 driver loader. Unlike <code>egl_glx</code>, it has no dependency on
+<code>libGL</code>. It talks to the X server directly using DRI2 protocol.</p>
</li>
<li><code>egl_dri</code>
<p>This driver lacks maintenance and does <em>not</em> build. It is similiar
-to <code>egl_xdri</code> in that it functions as a DRI driver loader. But
-unlike <code>egl_xdri</code>, it supports Linux framebuffer devices as its
-window system and supports EGL_MESA_screen_surface extension. It loads only
-DRI1 drivers. As DRI1 drivers is phasing out, it might be better to rewrite
-the driver to support KMS and DRI2.</p>
+to <code>egl_dri2</code> in that it functions as a DRI(1) driver loader. But
+unlike <code>egl_dri2</code>, it supports Linux framebuffer devices as its
+window system and supports EGL_MESA_screen_surface extension. As DRI1 drivers
+are phasing out, it might eventually be replaced by <code>egl_dri2</code>.</p>
</li>
</ul>
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><code>EGLDisplay</code> Mutex</h3>
+
+The <code>EGLDisplay</code> will be locked before calling any of the dispatch
+functions (well, except for GetProcAddress which does not take an
+<code>EGLDisplay</code>). This guarantees that the same dispatch function will
+not be called with the sample display at the same time. If a driver has access
+to an <code>EGLDisplay</code> without going through the EGL APIs, the driver
+should as well lock the display before using it.
+
<h3>TODOs</h3>
<ul>
-<li>Thread safety</li>
<li>Pass the conformance tests</li>
<li>Better automatic driver selection: <code>EGL_DISPLAY</code> loads all
drivers and might eat too much memory.</li>
-<li>Stop using <code>glxinit.c</code> and sources from <code>src/glx/x11/</code></li>
</ul>
projects / mesa.git / blobdiff