i965: Drop broken front_buffer_reading/drawing optimization.

The flag wasn't getting updated correctly when the ctx->DrawBuffer or
ctx->ReadBuffer changed.  It usually ended up working out because most
apps only have one window system framebuffer, or if they have more than
one and they have any front read/drawing, they will have called
glReadBuffer()/glDrawBuffer() on it when they get started on the new
buffer.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>

1 files changed, 27 insertions, 17 deletions

diff --git a/src/mesa/drivers/dri/i965/intel_buffers.c b/src/mesa/drivers/dri/i965/intel_buffers.c
index 1ece875..23d936f 100644
--- a/src/mesa/drivers/dri/i965/intel_buffers.c
+++ b/src/mesa/drivers/dri/i965/intel_buffers.c
@@ -53,22 +53,36 @@ intel_check_front_buffer_rendering(struct brw_context *brw)
    }
 }
 
+bool
+brw_is_front_buffer_reading(struct gl_framebuffer *fb)
+{
+   if (!fb || _mesa_is_user_fbo(fb))
+      return false;
+
+   return fb->_ColorReadBufferIndex == BUFFER_FRONT_LEFT;
+}
+
+bool
+brw_is_front_buffer_drawing(struct gl_framebuffer *fb)
+{
+   if (!fb || _mesa_is_user_fbo(fb))
+      return false;
+
+   return (fb->_NumColorDrawBuffers >= 1 &&
+           fb->_ColorDrawBufferIndexes[0] == BUFFER_FRONT_LEFT);
+}
+
 static void
 intelDrawBuffer(struct gl_context * ctx, GLenum mode)
 {
-   if (ctx->DrawBuffer && _mesa_is_winsys_fbo(ctx->DrawBuffer)) {
+   if (brw_is_front_buffer_drawing(ctx->DrawBuffer)) {
       struct brw_context *const brw = brw_context(ctx);
-      const bool was_front_buffer_rendering = brw->is_front_buffer_rendering;
 
-      brw->is_front_buffer_rendering = (mode == GL_FRONT_LEFT)
-	|| (mode == GL_FRONT) || (mode == GL_FRONT_AND_BACK);
-
-      /* If we weren't front-buffer rendering before but we are now,
-       * invalidate our DRI drawable so we'll ask for new buffers
+      /* If we might be front-buffer rendering on this buffer for the first
+       * time, invalidate our DRI drawable so we'll ask for new buffers
        * (including the fake front) before we start rendering again.
        */
-      if (!was_front_buffer_rendering && brw->is_front_buffer_rendering)
-	 dri2InvalidateDrawable(brw->driContext->driDrawablePriv);
+      dri2InvalidateDrawable(brw->driContext->driDrawablePriv);
    }
 }
 
@@ -76,18 +90,14 @@ intelDrawBuffer(struct gl_context * ctx, GLenum mode)
 static void
 intelReadBuffer(struct gl_context * ctx, GLenum mode)
 {
-   if (ctx->ReadBuffer && _mesa_is_winsys_fbo(ctx->ReadBuffer)) {
+   if (brw_is_front_buffer_reading(ctx->ReadBuffer)) {
       struct brw_context *const brw = brw_context(ctx);
-      const bool was_front_buffer_reading = brw->is_front_buffer_reading;
-
-      brw->is_front_buffer_reading = mode == GL_FRONT_LEFT || mode == GL_FRONT;
 
-      /* If we weren't front-buffer reading before but we are now,
-       * invalidate our DRI drawable so we'll ask for new buffers
+      /* If we might be front-buffer reading on this buffer for the first
+       * time, invalidate our DRI drawable so we'll ask for new buffers
        * (including the fake front) before we start reading again.
        */
-      if (!was_front_buffer_reading && brw->is_front_buffer_reading)
-	 dri2InvalidateDrawable(brw->driContext->driReadablePriv);
+      dri2InvalidateDrawable(brw->driContext->driReadablePriv);
    }
 }