Fix flickering when switching VT

backend/drm/drm.c

@@ -192,6 +192,9 @@ static bool wlr_drm_connector_make_current(struct wlr_output *output,
 static bool wlr_drm_connector_swap_buffers(struct wlr_output *output) {
 	struct wlr_drm_connector *conn = (struct wlr_drm_connector *)output;
 	struct wlr_drm_backend *drm = (struct wlr_drm_backend *)output->backend;
+	if (!drm->session->active) {
+		return false;
+	}
 
 	struct wlr_drm_crtc *crtc = conn->crtc;
 	if (!crtc) {
@@ -516,6 +519,10 @@ static bool wlr_drm_connector_set_cursor(struct wlr_output *output,
 	struct wlr_drm_backend *drm = (struct wlr_drm_backend *)output->backend;
 	struct wlr_drm_renderer *renderer = &drm->renderer;
 
+	if (!drm->session->active) {
+		return false;
+	}
+
 	struct wlr_drm_crtc *crtc = conn->crtc;
 	if (!crtc) {
 		return false;
@@ -644,6 +651,9 @@ static bool wlr_drm_connector_move_cursor(struct wlr_output *output,
 		int x, int y) {
 	struct wlr_drm_connector *conn = (struct wlr_drm_connector *)output;
 	struct wlr_drm_backend *drm = (struct wlr_drm_backend *)output->backend;
+	if (!drm->session->active) {
+		return false;
+	}
 	if (!conn->crtc) {
 		return false;
 	}

rootston/output.c

@@ -419,8 +419,6 @@ static void render_output(struct roots_output *output) {
 		goto renderer_end;
 	}
 
-	wlr_renderer_clear(output->desktop->server->renderer, 1, 1, 1, 1);
-
 	int nrects;
 	pixman_box32_t *rects = pixman_region32_rectangles(&damage, &nrects);
 	for (int i = 0; i < nrects; ++i) {

types/wlr_output.c

@@ -184,11 +184,6 @@ 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);