Add post_frame event to wlr_output, use wlr_drm_plane_make_current in…

… wlr_drm_output_read_pixels

backend/drm/drm.c

@@ -636,9 +636,9 @@ static bool wlr_drm_connector_move_cursor(struct wlr_output *output,
 
 static void wlr_drm_connector_read_pixels(struct wlr_output *_output,
 		void *out_data) {
-	struct wlr_drm_output *output = (struct wlr_drm_output *)_output;
-	struct wlr_drm_crtc *crtc = output->crtc;
-	struct wlr_drm_plane *plane = crtc->primary;
+	struct wlr_drm_connector *conn = (struct wlr_drm_connector *)output;
+	struct wlr_drm_plane *plane = conn->crtc->primary;
+	wlr_drm_plane_make_current(conn->renderer, plane);
 	glReadPixels(0, 0, plane->width, plane->height, GL_BGRA_EXT, GL_UNSIGNED_BYTE,
 		out_data);
 }
@@ -846,6 +846,7 @@ static void page_flip_handler(int fd, unsigned seq,
 
 	if (drm->session->active) {
 		wl_signal_emit(&conn->output.events.frame, &conn->output);
+		wl_signal_emit(&conn->output.events.post_frame, &conn->output);
 	}
 }
 

include/wlr/types/wlr_output.h

@@ -37,6 +37,7 @@ struct wlr_output {
 
 	struct {
 		struct wl_signal frame;
+		struct wl_signal post_frame;
 		struct wl_signal resolution;
 		struct wl_signal destroy;
 	} events;

types/wlr_output.c

@@ -105,6 +105,7 @@ void wlr_output_init(struct wlr_output *output,
 	output->transform = WL_OUTPUT_TRANSFORM_NORMAL;
 	output->scale = 1;
 	wl_signal_init(&output->events.frame);
+	wl_signal_init(&output->events.post_frame);
 	wl_signal_init(&output->events.resolution);
 	wl_signal_init(&output->events.destroy);
 }

types/wlr_screenshooter.c

@@ -59,7 +59,7 @@ static void screenshooter_shoot(struct wl_client *client,
 	state->output = output;
 	state->screenshot = screenshot;
 	state->frame_listener.notify = output_frame_notify;
-	wl_signal_add(&output->events.frame, &state->frame_listener);
+	wl_signal_add(&output->events.post_frame, &state->frame_listener);
 }
 
 static struct orbital_screenshooter_interface screenshooter_impl = {