backend/x11: report adaptive sync as enabled

All we can do to influence adaptive sync on the X11 backend is set the
_VARIABLE_REFRESH window property like mesa automatically does. We don't
have any control beyond that, so we set the state to enabled on creating
the output and never allow changing it (just like the Wayland backend).

backend/x11/output.c

@@ -113,6 +113,17 @@ static bool output_test(struct wlr_output *wlr_output,
 		return false;
 	}
 
+	// All we can do to influence adaptive sync on the X11 backend is set the
+	// _VARIABLE_REFRESH window property like mesa automatically does. We don't
+	// have any control beyond that, so we set the state to enabled on creating
+	// the output and never allow changing it (just like the Wayland backend).
+	assert(wlr_output->adaptive_sync_status == WLR_OUTPUT_ADAPTIVE_SYNC_ENABLED);
+	if (state->committed & WLR_OUTPUT_STATE_ADAPTIVE_SYNC_ENABLED) {
+		if (!state->adaptive_sync_enabled) {
+			return false;
+		}
+	}
+
 	if (state->committed & WLR_OUTPUT_STATE_MODE) {
 		assert(state->mode_type == WLR_OUTPUT_STATE_MODE_CUSTOM);
 	}
@@ -335,21 +346,6 @@ static bool output_commit(struct wlr_output *wlr_output,
 		}
 	}
 
-	if (state->committed & WLR_OUTPUT_STATE_ADAPTIVE_SYNC_ENABLED &&
-			x11->atoms.variable_refresh != XCB_ATOM_NONE) {
-		if (state->adaptive_sync_enabled) {
-			uint32_t enabled = 1;
-			xcb_change_property(x11->xcb, XCB_PROP_MODE_REPLACE, output->win,
-				x11->atoms.variable_refresh, XCB_ATOM_CARDINAL, 32, 1,
-				&enabled);
-			wlr_output->adaptive_sync_status = WLR_OUTPUT_ADAPTIVE_SYNC_UNKNOWN;
-		} else {
-			xcb_delete_property(x11->xcb, output->win,
-				x11->atoms.variable_refresh);
-			wlr_output->adaptive_sync_status = WLR_OUTPUT_ADAPTIVE_SYNC_DISABLED;
-		}
-	}
-
 	if (state->committed & WLR_OUTPUT_STATE_BUFFER) {
 		if (!output_commit_buffer(output, state)) {
 			return false;
@@ -574,6 +570,12 @@ struct wlr_output *wlr_x11_output_create(struct wlr_backend *backend) {
 		x11->atoms.wm_protocols, XCB_ATOM_ATOM, 32, 1,
 		&x11->atoms.wm_delete_window);
 
+	uint32_t enabled = 1;
+	xcb_change_property(x11->xcb, XCB_PROP_MODE_REPLACE, output->win,
+		x11->atoms.variable_refresh, XCB_ATOM_CARDINAL, 32, 1,
+		&enabled);
+	wlr_output->adaptive_sync_status = WLR_OUTPUT_ADAPTIVE_SYNC_ENABLED;
+
 	wlr_x11_output_set_title(wlr_output, NULL);
 
 	xcb_map_window(x11->xcb, output->win);