output: fail commits if adaptive sync cannot be enabled

Previously, adaptive sync was just a hint and wouldn't make any
atomic commit fail if the backend didn't support it. The main reason
is wlr_output_test wasn't supported at the time.

Now that we have a way for compositors to test whether a change can
work, let's remove the exception for adaptive sync and convert it to
a regular output state field.

backend/drm/atomic.c

@@ -254,8 +254,10 @@ static bool atomic_crtc_commit(struct wlr_drm_connector *conn,
 	bool prev_vrr_enabled =
 		output->adaptive_sync_status == WLR_OUTPUT_ADAPTIVE_SYNC_ENABLED;
 	bool vrr_enabled = prev_vrr_enabled;
-	if ((state->base->committed & WLR_OUTPUT_STATE_ADAPTIVE_SYNC_ENABLED) &&
-			drm_connector_supports_vrr(conn)) {
+	if ((state->base->committed & WLR_OUTPUT_STATE_ADAPTIVE_SYNC_ENABLED)) {
+		if (!drm_connector_supports_vrr(conn)) {
+			return false;
+		}
 		vrr_enabled = state->base->adaptive_sync_enabled;
 	}
 

backend/drm/drm.c

@@ -36,7 +36,8 @@ static const uint32_t COMMIT_OUTPUT_STATE =
 	WLR_OUTPUT_STATE_BUFFER |
 	WLR_OUTPUT_STATE_MODE |
 	WLR_OUTPUT_STATE_ENABLED |
-	WLR_OUTPUT_STATE_GAMMA_LUT;
+	WLR_OUTPUT_STATE_GAMMA_LUT |
+	WLR_OUTPUT_STATE_ADAPTIVE_SYNC_ENABLED;
 
 static const uint32_t SUPPORTED_OUTPUT_STATE =
 	WLR_OUTPUT_STATE_BACKEND_OPTIONAL | COMMIT_OUTPUT_STATE;
@@ -489,6 +490,12 @@ static bool drm_connector_test(struct wlr_output *output,
 		}
 	}
 
+	if ((state->committed & WLR_OUTPUT_ADAPTIVE_SYNC_ENABLED) &&
+			state->adaptive_sync_enabled &&
+			!drm_connector_supports_vrr(conn)) {
+		return false;
+	}
+
 	struct wlr_drm_connector_state pending = {0};
 	drm_connector_state_init(&pending, conn, state);
 

backend/drm/legacy.c

@@ -115,8 +115,10 @@ static bool legacy_crtc_commit(struct wlr_drm_connector *conn,
 		}
 	}
 
-	if ((state->base->committed & WLR_OUTPUT_STATE_ADAPTIVE_SYNC_ENABLED) &&
-			drm_connector_supports_vrr(conn)) {
+	if (state->base->committed & WLR_OUTPUT_STATE_ADAPTIVE_SYNC_ENABLED) {
+		if (!drm_connector_supports_vrr(conn)) {
+			return false;
+		}
 		if (drmModeObjectSetProperty(drm->fd, crtc->id, DRM_MODE_OBJECT_CRTC,
 				crtc->props.vrr_enabled,
 				state->base->adaptive_sync_enabled) != 0) {

backend/x11/output.c

@@ -26,7 +26,8 @@
 static const uint32_t SUPPORTED_OUTPUT_STATE =
 	WLR_OUTPUT_STATE_BACKEND_OPTIONAL |
 	WLR_OUTPUT_STATE_BUFFER |
-	WLR_OUTPUT_STATE_MODE;
+	WLR_OUTPUT_STATE_MODE |
+	WLR_OUTPUT_STATE_ADAPTIVE_SYNC_ENABLED;
 
 static void parse_xcb_setup(struct wlr_output *output,
 		xcb_connection_t *xcb) {

include/wlr/interfaces/wlr_output.h

@@ -22,7 +22,6 @@
 	WLR_OUTPUT_STATE_SCALE | \
 	WLR_OUTPUT_STATE_TRANSFORM | \
 	WLR_OUTPUT_STATE_RENDER_FORMAT | \
-	WLR_OUTPUT_STATE_ADAPTIVE_SYNC_ENABLED | \
 	WLR_OUTPUT_STATE_SUBPIXEL)
 
 /**

include/wlr/types/wlr_output.h

@@ -301,7 +301,10 @@ void wlr_output_set_transform(struct wlr_output *output,
 	enum wl_output_transform transform);
 /**
  * Enables or disables adaptive sync (ie. variable refresh rate) on this
- * output. This is just a hint, the backend is free to ignore this setting.
+ * output. On some backends, this is just a hint and may be ignored.
+ * Compositors can inspect `wlr_output.adaptive_sync_status` to query the
+ * effective status. Backends that don't support adaptive sync will reject
+ * the output commit.
  *
  * When enabled, compositors can submit frames a little bit later than the
  * deadline without dropping a frame.