Stop showing then hiding windows on starting designer in top-level mode.

We've had this since 4.5 and it's very annoying to see the window show
and quickly hide itself. I was hoping it wasn't a bug in Qt, and it
turns it isn't and it was happening on all platforms.

Reviewed-by: Friedemann Kleint
Shout outs: João for testing.

1 files changed, 2 insertions, 3 deletions

diff --git a/tools/designer/src/designer/qdesigner_workbench.cpp b/tools/designer/src/designer/qdesigner_workbench.cpp
index 923687a2..ce8dde6 100644
--- a/tools/designer/src/designer/qdesigner_workbench.cpp
+++ b/tools/designer/src/designer/qdesigner_workbench.cpp
@@ -462,8 +462,7 @@ void QDesignerWorkbench::switchToTopLevelMode()
     // make sure that the widgetbox is visible if it is different from neutral.
     QDesignerToolWindow *widgetBoxWrapper = widgetBoxToolWindow();
     Q_ASSERT(widgetBoxWrapper);
-    if (!widgetBoxWrapper->action()->isChecked())
-        widgetBoxWrapper->action()->trigger();
+    const bool needWidgetBoxWrapperVisible = widgetBoxWrapper->action()->isChecked();
 
     switchToNeutralMode();
     const QPoint desktopOffset = desktopGeometry().topLeft();
@@ -502,7 +501,7 @@ void QDesignerWorkbench::switchToTopLevelMode()
         found_visible_window |= tw->isVisible();
     }
 
-    if (!widgetBoxWrapper->action()->isChecked())
+    if (needWidgetBoxWrapperVisible)
         widgetBoxWrapper->action()->trigger();
 
     if (!m_toolWindows.isEmpty() && !found_visible_window)