output: atomic mode, enabled, scale and transform

This commit makes more output properties (mode, enabled, scale and transform)
atomic. This means that they are double-buffered and only applied on commit.

Compositors now need to call wlr_output_commit after setting any of those
properties.

Internally, backends still apply properties sequentially. The behaviour should
be exactly the same as before. Future commits will update some backends to take
advantage of the atomic interface. Some backends are non-atomic by design, e.g.
the X11 backend or the legacy DRM backend.

Updates: https://github.com/swaywm/wlroots/issues/1640

1 files changed, 32 insertions, 6 deletions

diff --git a/backend/drm/drm.c b/backend/drm/drm.c
index eef7beb5..730240c8 100644
--- a/backend/drm/drm.c
+++ b/backend/drm/drm.c
@@ -328,12 +328,9 @@ static bool drm_connector_attach_render(struct wlr_output *output,
 	return make_drm_surface_current(&conn->crtc->primary->surf, buffer_age);
 }
 
-static bool drm_connector_commit(struct wlr_output *output) {
+static bool drm_connector_commit_buffer(struct wlr_output *output) {
 	struct wlr_drm_connector *conn = get_drm_connector_from_output(output);
 	struct wlr_drm_backend *drm = get_drm_backend_from_backend(output->backend);
-	if (!drm->session->active) {
-		return false;
-	}
 
 	struct wlr_drm_crtc *crtc = conn->crtc;
 	if (!crtc) {
@@ -404,6 +401,37 @@ static bool drm_connector_commit(struct wlr_output *output) {
 	return true;
 }
 
+static bool drm_connector_commit(struct wlr_output *output) {
+	struct wlr_drm_backend *drm = get_drm_backend_from_backend(output->backend);
+
+	if (!drm->session->active) {
+		return false;
+	}
+
+	if (output->pending.committed & WLR_OUTPUT_STATE_ENABLED) {
+		if (!enable_drm_connector(output, output->pending.enabled)) {
+			return false;
+		}
+	}
+
+	if (output->pending.committed & WLR_OUTPUT_STATE_MODE) {
+		if (output->pending.mode_type != WLR_OUTPUT_STATE_MODE_FIXED) {
+			return false;
+		}
+		if (!drm_connector_set_mode(output, output->pending.mode)) {
+			return false;
+		}
+	}
+
+	if (output->pending.committed & WLR_OUTPUT_STATE_BUFFER) {
+		if (!drm_connector_commit_buffer(output)) {
+			return false;
+		}
+	}
+
+	return true;
+}
+
 static void fill_empty_gamma_table(size_t size,
 		uint16_t *r, uint16_t *g, uint16_t *b) {
 	for (uint32_t i = 0; i < size; ++i) {
@@ -922,8 +950,6 @@ static void drm_connector_destroy(struct wlr_output *output) {
 }
 
 static const struct wlr_output_impl output_impl = {
-	.enable = enable_drm_connector,
-	.set_mode = drm_connector_set_mode,
 	.set_cursor = drm_connector_set_cursor,
 	.move_cursor = drm_connector_move_cursor,
 	.destroy = drm_connector_destroy,