backend/drm: extract post-commit logic into functions

It's more readable, and we'll soon call this from a loop for
multi-connector commits.

backend/drm/drm.c

@@ -449,24 +449,11 @@ static struct wlr_drm_page_flip *drm_page_flip_create(struct wlr_drm_connector *
 	return page_flip;
 }
 
-static bool drm_crtc_commit(struct wlr_drm_connector *conn,
-		const struct wlr_drm_connector_state *state,
-		uint32_t flags, bool test_only) {
-	// Disallow atomic-only flags
-	assert((flags & ~DRM_MODE_PAGE_FLIP_FLAGS) == 0);
-
-	struct wlr_drm_page_flip *page_flip = NULL;
-	if (flags & DRM_MODE_PAGE_FLIP_EVENT) {
-		page_flip = drm_page_flip_create(conn);
-		if (page_flip == NULL) {
-			return false;
-		}
-	}
-
-	struct wlr_drm_backend *drm = conn->backend;
+static void drm_connector_apply_commit(const struct wlr_drm_connector_state *state,
+		struct wlr_drm_page_flip *page_flip) {
+	struct wlr_drm_connector *conn = state->connector;
 	struct wlr_drm_crtc *crtc = conn->crtc;
-	bool ok = drm->iface->crtc_commit(conn, state, page_flip, flags, test_only);
-	if (ok && !test_only) {
+
 	drm_fb_copy(&crtc->primary->queued_fb, state->primary_fb);
 	if (crtc->cursor != NULL) {
 		drm_fb_copy(&crtc->cursor->queued_fb, state->cursor_fb);
@@ -483,7 +470,11 @@ static bool drm_crtc_commit(struct wlr_drm_connector *conn,
 	if (state->base->committed & WLR_OUTPUT_STATE_MODE) {
 		conn->refresh = calculate_refresh_rate(&state->mode);
 	}
-	} else {
+}
+
+static void drm_connector_rollback_commit(const struct wlr_drm_connector_state *state) {
+	struct wlr_drm_crtc *crtc = state->connector->crtc;
+
 	// The set_cursor() hook is a bit special: it's not really synchronized
 	// to commit() or test(). Once set_cursor() returns true, the new
 	// cursor is effectively committed. So don't roll it back here, or we
@@ -495,7 +486,28 @@ static bool drm_crtc_commit(struct wlr_drm_connector *conn,
 	wl_list_for_each(layer, &crtc->layers, link) {
 		drm_fb_clear(&layer->pending_fb);
 	}
+}
 
+static bool drm_crtc_commit(struct wlr_drm_connector *conn,
+		const struct wlr_drm_connector_state *state,
+		uint32_t flags, bool test_only) {
+	// Disallow atomic-only flags
+	assert((flags & ~DRM_MODE_PAGE_FLIP_FLAGS) == 0);
+
+	struct wlr_drm_page_flip *page_flip = NULL;
+	if (flags & DRM_MODE_PAGE_FLIP_EVENT) {
+		page_flip = drm_page_flip_create(conn);
+		if (page_flip == NULL) {
+			return false;
+		}
+	}
+
+	struct wlr_drm_backend *drm = conn->backend;
+	bool ok = drm->iface->crtc_commit(conn, state, page_flip, flags, test_only);
+	if (ok && !test_only) {
+		drm_connector_apply_commit(state, page_flip);
+	} else {
+		drm_connector_rollback_commit(state);
 		drm_page_flip_destroy(page_flip);
 	}
 	return ok;