i965: Do not set front_buffer_dirty if there is no front buffer

Otherwise there will be a warning:
 "libEGL warning: FIXME: egl/x11 doesn't support front buffer rendering."

Happens with EGL_KHR_surfaceless_context:

 eglMakeCurrent(egl_display, EGL_NO_SURFACE, EGL_NO_SURFACE, egl_context)
 eglMakeCurrent(egl_display, egl_surface, egl_surface, egl_context)
 glFlush() // Here will be a warning

Cc: <mesa-stable@lists.freedesktop.org>
Closes: https://gitlab.freedesktop.org/mesa/mesa/issues/1525
Signed-off-by: Danylo Piliaiev <danylo.piliaiev@globallogic.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3628>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3628>

diff --git a/src/mesa/drivers/dri/i965/brw_context.c b/src/mesa/drivers/dri/i965/brw_context.c
index 2676382..16f9878 100644 (file)
--- a/src/mesa/drivers/dri/i965/brw_context.c
+++ b/src/mesa/drivers/dri/i965/brw_context.c
@@ -1523,8 +1523,10 @@ intel_prepare_render(struct brw_context *brw)
     * that will happen next will probably dirty the front buffer.  So
     * mark it as dirty here.
     */
-   if (_mesa_is_front_buffer_drawing(ctx->DrawBuffer))
+   if (_mesa_is_front_buffer_drawing(ctx->DrawBuffer) &&
+       ctx->DrawBuffer != _mesa_get_incomplete_framebuffer()) {
       brw->front_buffer_dirty = true;
+   }
 
    if (brw->is_shared_buffer_bound) {
       /* Subsequent rendering will probably dirty the shared buffer. */