Optimize resetOptimalWidth()

Don't call this method directly on every demand, but schedule
a call instead and invoke it once after the current call
returns back to the main loop.

The single call may cost up to ~20ms, and when we call it for
every target having 5000 targets, the total cost is up to ~10 seconds
(every call removes one items, so subsequent calls take a bit
less time). This happens on shutdown when Qt6 project was loaded.
The shutdown time went down from ~15 seconds to ~4 seconds with
this patch.

Change-Id: Id821d72cd8e1dd949112d9167b7736a267b221fc
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/projectexplorer/miniprojecttargetselector.cpp

@@ -238,6 +238,18 @@ public:
 protected:
     void resetOptimalWidth()
     {
+        if (m_resetScheduled)
+            return;
+        m_resetScheduled = true;
+        QMetaObject::invokeMethod(this, &SelectorView::doResetOptimalWidth, Qt::QueuedConnection);
+    }
+
+private:
+    void keyPressEvent(QKeyEvent *event) override;
+    void keyReleaseEvent(QKeyEvent *event) override;
+    void doResetOptimalWidth()
+    {
+        m_resetScheduled = false;
         int width = 0;
         QFontMetrics fn(font());
         theModel()->forItemsAtLevel<1>([this, &width, &fn](const GenericItem *item) {
@@ -246,12 +258,9 @@ protected:
         setOptimalWidth(width);
     }
 
-private:
-    void keyPressEvent(QKeyEvent *event) override;
-    void keyReleaseEvent(QKeyEvent *event) override;
-
     int m_maxCount = 0;
     int m_optimalWidth = 0;
+    bool m_resetScheduled = false;
 };
 
 class ProjectListView : public SelectorView