output: don't emit the mode event if it hasn't changed

This also fixes #535.

backend/drm/drm.c

@@ -496,11 +496,15 @@ static bool wlr_drm_connector_set_mode(struct wlr_output *output,
 	conn->state = WLR_DRM_CONN_CONNECTED;
 	wlr_output_update_mode(&conn->output, mode);
 
+	// When switching VTs, the mode is not updated but the buffers become
+	// invalid, so we need to manually damage the output here
+	wlr_output_damage_whole(&conn->output);
+
 	// Since realloc_crtcs can deallocate planes on OTHER outputs,
-	// we actually need to reinitialize any than has changed
+	// we actually need to reinitialize any that has changed
 	ssize_t output_index = -1;
 	wl_list_for_each(conn, &drm->outputs, link) {
-		output_index += 1;
+		output_index++;
 		struct wlr_output_mode *mode = conn->output.current_mode;
 		struct wlr_drm_crtc *crtc = conn->crtc;
 

include/wlr/interfaces/wlr_output.h

@@ -33,6 +33,7 @@ void wlr_output_update_custom_mode(struct wlr_output *output, int32_t width,
 	int32_t height, int32_t refresh);
 void wlr_output_update_enabled(struct wlr_output *output, bool enabled);
 void wlr_output_update_needs_swap(struct wlr_output *output);
+void wlr_output_damage_whole(struct wlr_output *output);
 void wlr_output_send_frame(struct wlr_output *output);
 
 #endif

types/wlr_output.c

@@ -178,6 +178,11 @@ void wlr_output_update_mode(struct wlr_output *output,
 
 void wlr_output_update_custom_mode(struct wlr_output *output, int32_t width,
 		int32_t height, int32_t refresh) {
+	if (output->width == width && output->height == height &&
+			output->refresh == refresh) {
+		return;
+	}
+
 	output->width = width;
 	output->height = height;
 	wlr_output_update_matrix(output);
@@ -563,7 +568,7 @@ void wlr_output_update_needs_swap(struct wlr_output *output) {
 	wlr_signal_emit_safe(&output->events.needs_swap, output);
 }
 
-static void output_damage_whole(struct wlr_output *output) {
+void wlr_output_damage_whole(struct wlr_output *output) {
 	int width, height;
 	wlr_output_transformed_resolution(output, &width, &height);
 
@@ -577,7 +582,7 @@ static void output_fullscreen_surface_reset(struct wlr_output *output) {
 		wl_list_remove(&output->fullscreen_surface_commit.link);
 		wl_list_remove(&output->fullscreen_surface_destroy.link);
 		output->fullscreen_surface = NULL;
-		output_damage_whole(output);
+		wlr_output_damage_whole(output);
 	}
 }
 
@@ -591,7 +596,7 @@ static void output_fullscreen_surface_handle_commit(
 			output->fullscreen_height != surface->current->height) {
 		output->fullscreen_width = surface->current->width;
 		output->fullscreen_height = surface->current->height;
-		output_damage_whole(output);
+		wlr_output_damage_whole(output);
 		return;
 	}
 
@@ -627,7 +632,7 @@ void wlr_output_set_fullscreen_surface(struct wlr_output *output,
 	output_fullscreen_surface_reset(output);
 
 	output->fullscreen_surface = surface;
-	output_damage_whole(output);
+	wlr_output_damage_whole(output);
 
 	if (surface == NULL) {
 		return;