perf(bar): 仅在 bar 需要绘制新内容时才重绘并 flush 后端

src/bar/bar.c

@@ -302,8 +302,6 @@ static inline bool bar_output_is_dirty(bar_output_t *bar_output) {
 }
 
 static void bar_output_draw(bar_output_t *bar_output, text_context_t *ctx) {
-  if (!bar_output_is_dirty(bar_output)) return;
-
   auto cr = bar_output->cr;
 
   auto left = &bar_output->left;
@@ -318,12 +316,19 @@ static void bar_output_draw(bar_output_t *bar_output, text_context_t *ctx) {
   bar_item_draw(cr, &bar_output->center, ctx, bar_output->height);
 }
 
-void bar_draw(bar_t *bar) {
+bool bar_draw(bar_t *bar) {
   auto ctx = bar->ctx;
 
+  bool changed = false;
+
   for (size_t i = 0; i < bar->count; ++i) {
     auto bar_output = &bar->bars[i];
+    if (!bar_output_is_dirty(bar_output)) continue;
+
     bar_output_layout(bar_output, ctx);
     bar_output_draw(bar_output, ctx);
+    changed = true;
   }
+
+  return changed;
 }

src/bar/bar.h

@@ -41,4 +41,4 @@ typedef struct bar_t {
 void bar_init(bar_t *bar, listeners_t *listeners);
 void bar_cleanup(bar_t *bar);
 void bar_update(bar_t *bar);
-void bar_draw(bar_t *bar);
+bool bar_draw(bar_t *bar);

src/runtime/runtime.c

@@ -487,8 +487,7 @@ static inline void runtime_update_bar(runtime_t *runtime) {
   if (!bar->visible) return;
 
   bar_update(bar);
-  bar_draw(bar);
+  if (bar_draw(bar)) backend_flush(runtime->backend);
-  backend_flush(runtime->backend);
 }
 
 static void runtime_run_event_loop(runtime_t *runtime) {