[RFC] mesa: drop current draw/read buffer when ctx is released

[Rob Clark]

So, not quite sure if this is the *correct* solution, but it is at least
*a* solution to a problem with android wallpaper vs mesa that I've been
debugging.  Basically, what happens is:

   EGLSurface tmpSurface = mEgl.eglCreatePbufferSurface(mEglDisplay, mEglConfig, attribs);
   mEgl.eglMakeCurrent(mEglDisplay, tmpSurface, tmpSurface, mEglContext);

   int[] maxSize = new int[1];
   Rect frame = surfaceHolder.getSurfaceFrame();
   glGetIntegerv(GL_MAX_TEXTURE_SIZE, maxSize, 0);

   mEgl.eglMakeCurrent(mEglDisplay, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
   mEgl.eglDestroySurface(mEglDisplay, tmpSurface);

   ... check maxSize vs frame size and bail if needed ...

   mEglSurface = mEgl.eglCreateWindowSurface(mEglDisplay, mEglConfig, surfaceHolder, null);
   ... error checking ...
   mEgl.eglMakeCurrent(mEglDisplay, mEglSurface, mEglSurface, mEglContext);

When the window-surface is created, it ends up with the same ptr address
as the recently freed tmpSurface pbuffer surface.  Which after many
levels of indirection, results in st_framebuffer_validate() ending up with
the same/old framebuffer object, and in the end never calling the
DRIimageLoaderExtension::getBuffers().  Then in droid_swap_buffers(), the
dri2_surf is still the old pbuffer surface (with dri2_surf->buffer being
NULL, obviously, so when wallpaper app calls eglSwapBuffers() nothing
gets enqueued to the compositor).

Maybe instead, eglDestroySurface() should clear any references the ctx
has to the surface.  Not sure how that would work.  Did I mention there
are many levels of indirection?
---
 src/mesa/main/context.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/mesa/main/context.c b/src/mesa/main/context.c
index 5e52065..83b8cc1 100644
--- a/src/mesa/main/context.c
+++ b/src/mesa/main/context.c
@@ -1646,6 +1646,10 @@ ALOGE("%s:%d, drawBuffer=%p, readBuffer=%p", __func__, __LINE__, drawBuffer, rea
 
    if (!newCtx) {
       _glapi_set_dispatch(NULL);  /* none current */
+      if (curCtx) {
+         _mesa_reference_framebuffer(&curCtx->WinSysDrawBuffer, NULL);
+         _mesa_reference_framebuffer(&curCtx->WinSysReadBuffer, NULL);
+      }
    }
    else {
       _glapi_set_dispatch(newCtx->CurrentDispatch);
-- 
2.1.0