backend-drm: Move overlay vs. primary plane check earlier

For views which cover the entire output, we always attempt to place them
on the primary plane, to avoid a situation where we place a fullscreen
view into an overlay plane and then have to disable the primary plane,
which doesn't always work.

Move this check earlier, so we don't consider overlay planes to be
candidates for fullscreen views. This check should be changed in future
to only filter for opaque views, but that's for another time.

Signed-off-by: Daniel Stone <daniels@collabora.com>

libweston/backend-drm/state-propose.c

@@ -378,9 +378,6 @@ drm_output_try_view_on_plane(struct drm_plane *plane,
 			     struct drm_fb *fb, uint64_t zpos)
 {
 	struct drm_backend *b = state->pending_state->backend;
-	struct weston_output *wet_output = &state->output->base;
-	bool view_matches_entire_output, scanout_has_view_assigned;
-	struct drm_plane *scanout_plane = state->output->scanout_plane;
 	struct drm_plane_state *ps = NULL;
 	const char *p_name = drm_output_get_plane_type_name(plane);
 	struct weston_surface *surface = ev->surface;
@@ -402,20 +399,6 @@ drm_output_try_view_on_plane(struct drm_plane *plane,
 			availability = PLACED_ON_PLANE;
 		break;
 	case WDRM_PLANE_TYPE_OVERLAY:
-		/* do not attempt to place it in the overlay if we don't have
-		 * anything in the scanout/primary and the view doesn't cover
-		 * the entire output  */
-		view_matches_entire_output =
-			weston_view_matches_output_entirely(ev, wet_output);
-		scanout_has_view_assigned =
-			drm_output_check_plane_has_view_assigned(scanout_plane,
-								 state);
-
-		if (view_matches_entire_output && !scanout_has_view_assigned) {
-			availability = NO_PLANES_ACCEPTED;
-			goto out;
-		}
-
 		ps = drm_output_prepare_overlay_view(plane, state, ev, mode,
 						     fb, zpos);
 		if (ps)
@@ -432,7 +415,6 @@ drm_output_try_view_on_plane(struct drm_plane *plane,
 		break;
 	}
 
-out:
 	switch (availability) {
 	case NO_PLANES:
 		/* set initial to this catch-all case, such that
@@ -618,6 +600,7 @@ drm_output_prepare_plane_view(struct drm_output_state *state,
 	struct wl_shm_buffer *shmbuf;
 	struct drm_fb *fb = NULL;
 
+	bool view_matches_entire_output, scanout_has_view_assigned;
 	uint32_t possible_plane_mask = 0;
 
 	/* check view for valid buffer, doesn't make sense to even try */
@@ -660,6 +643,12 @@ drm_output_prepare_plane_view(struct drm_output_state *state,
 		possible_plane_mask = fb->plane_mask;
 	}
 
+	view_matches_entire_output =
+		weston_view_matches_output_entirely(ev, &output->base);
+	scanout_has_view_assigned =
+		drm_output_check_plane_has_view_assigned(output->scanout_plane,
+							 state);
+
 	/* assemble a list with possible candidates */
 	wl_list_for_each(plane, &b->plane_list, link) {
 		const char *p_name = drm_output_get_plane_type_name(plane);
@@ -688,6 +677,11 @@ drm_output_prepare_plane_view(struct drm_output_state *state,
 		case WDRM_PLANE_TYPE_OVERLAY:
 			assert(fb);
 			assert(mode != DRM_OUTPUT_PROPOSE_STATE_RENDERER_ONLY);
+			/* if the view covers the whole output, put it in the
+			 * scanout plane, not overlay */
+			if (view_matches_entire_output &&
+			    !scanout_has_view_assigned)
+				continue;
 			break;
 		default:
 			assert(false && "unknown plane type");