output: trigger frame/present events on all commits on enabled output

Up until now, frame/present events were only triggered when the
user submitted a buffer. Change the wlr_output API so that these
events are triggered when any commit is applied on an enabled
output.

Closes: https://gitlab.freedesktop.org/wlroots/wlroots/-/issues/3708

backend/drm/drm.c

@@ -715,12 +715,10 @@ bool drm_connector_commit_state(struct wlr_drm_connector *conn,
 		}
 	}
 
-	uint32_t flags = 0;
 	if (pending.base->committed & WLR_OUTPUT_STATE_BUFFER) {
 		if (!drm_connector_state_update_primary_fb(conn, &pending)) {
 			goto out;
 		}
-		flags |= DRM_MODE_PAGE_FLIP_EVENT;
 
 		// wlr_drm_interface.crtc_commit will perform either a non-blocking
 		// page-flip, either a blocking modeset. When performing a blocking modeset
@@ -732,9 +730,6 @@ bool drm_connector_commit_state(struct wlr_drm_connector *conn,
 			goto out;
 		}
 	}
-	if (pending.modeset && pending.active) {
-		flags |= DRM_MODE_PAGE_FLIP_EVENT;
-	}
 	if (pending.base->committed & WLR_OUTPUT_STATE_LAYERS) {
 		if (!drm_connector_set_pending_layer_fbs(conn, pending.base)) {
 			return false;
@@ -751,6 +746,8 @@ bool drm_connector_commit_state(struct wlr_drm_connector *conn,
 		}
 	}
 
+	uint32_t flags = pending.active ? DRM_MODE_PAGE_FLIP_EVENT : 0;
+
 	ok = drm_crtc_commit(conn, &pending, flags, false);
 	if (!ok) {
 		goto out;

backend/headless/output.c

@@ -5,6 +5,7 @@
 #include <wlr/types/wlr_output_layer.h>
 #include <wlr/util/log.h>
 #include "backend/headless.h"
+#include "types/wlr_output.h"
 
 static const uint32_t SUPPORTED_OUTPUT_STATE =
 	WLR_OUTPUT_STATE_BACKEND_OPTIONAL |
@@ -65,7 +66,7 @@ static bool output_commit(struct wlr_output *wlr_output,
 		output_update_refresh(output, state->custom_mode.refresh);
 	}
 
-	if (state->committed & WLR_OUTPUT_STATE_BUFFER) {
+	if (output_pending_enabled(wlr_output, state)) {
 		struct wlr_output_event_present present_event = {
 			.commit_seq = wlr_output->commit_seq + 1,
 			.presented = true,

backend/wayland/output.c

@@ -19,6 +19,7 @@
 #include "backend/wayland.h"
 #include "render/pixel_format.h"
 #include "render/wlr_renderer.h"
+#include "types/wlr_output.h"
 
 #include "linux-dmabuf-unstable-v1-client-protocol.h"
 #include "presentation-time-client-protocol.h"
@@ -555,7 +556,7 @@ static bool output_commit(struct wlr_output *wlr_output,
 		return false;
 	}
 
-	if (state->committed & (WLR_OUTPUT_STATE_BUFFER | WLR_OUTPUT_STATE_LAYERS)) {
+	if (output_pending_enabled(wlr_output, state)) {
 		if (output->frame_callback != NULL) {
 			wl_callback_destroy(output->frame_callback);
 		}

backend/x11/output.c

@@ -22,6 +22,7 @@
 
 #include "backend/x11.h"
 #include "util/time.h"
+#include "types/wlr_output.h"
 
 static const uint32_t SUPPORTED_OUTPUT_STATE =
 	WLR_OUTPUT_STATE_BACKEND_OPTIONAL |
@@ -375,6 +376,10 @@ static bool output_commit(struct wlr_output *wlr_output,
 		if (!output_commit_buffer(output, state)) {
 			return false;
 		}
+	} else if (output_pending_enabled(wlr_output, state)) {
+		uint32_t serial = output->wlr_output.commit_seq;
+		uint64_t target_msc = output->last_msc ? output->last_msc + 1 : 0;
+		xcb_present_notify_msc(x11->xcb, output->win, serial, target_msc, 0, 0);
 	}
 
 	xcb_flush(x11->xcb);

include/types/wlr_output.h

@@ -6,6 +6,8 @@
 
 void output_pending_resolution(struct wlr_output *output,
 	const struct wlr_output_state *state, int *width, int *height);
+bool output_pending_enabled(struct wlr_output *output,
+	const struct wlr_output_state *state);
 
 bool output_pick_format(struct wlr_output *output,
 	const struct wlr_drm_format_set *display_formats,

include/wlr/types/wlr_output.h

@@ -170,7 +170,8 @@ struct wlr_output {
 		struct wl_signal precommit; // struct wlr_output_event_precommit
 		// Emitted right after commit
 		struct wl_signal commit; // struct wlr_output_event_commit
-		// Emitted right after the buffer has been presented to the user
+		// Emitted right after a commit has been presented to the user for
+		// enabled outputs
 		struct wl_signal present; // struct wlr_output_event_present
 		// Emitted after a client bound the wl_output global
 		struct wl_signal bind; // struct wlr_output_event_bind

types/output/output.c

@@ -319,7 +319,7 @@ static void output_apply_state(struct wlr_output *output,
 		output->cursor_swapchain = NULL;
 	}
 
-	if (state->committed & WLR_OUTPUT_STATE_BUFFER) {
+	if (output_pending_enabled(output, state)) {
 		output->frame_pending = true;
 		output->needs_frame = false;
 	}
@@ -592,6 +592,14 @@ void output_pending_resolution(struct wlr_output *output,
 	}
 }
 
+bool output_pending_enabled(struct wlr_output *output,
+		const struct wlr_output_state *state) {
+	if (state->committed & WLR_OUTPUT_STATE_ENABLED) {
+		return state->enabled;
+	}
+	return output->enabled;
+}
+
 /**
  * Compare a struct wlr_output_state with the current state of a struct
  * wlr_output.