From cf83c0b651790446c73dae29f68cec9e2ba6af9e Mon Sep 17 00:00:00 2001
From: Eike Ziller <eike.ziller@qt.io>
Date: Wed, 23 Apr 2025 16:31:05 +0200
Subject: [PATCH] QmlDesigner: Fix crash when switching to first .ui.qml file

if Qt Creator is already in Design mode.

QmlDesignerPlugin::showDesigner() was only called on a switch to Design
mode while the editor is a .ui.qml file. So it wasn't called when opening
a .ui file in Design mode and then switching to a .ui.qml file. But
showDesigner() creates the QmlDesigner widgets, so it must be called.

Fixes: QTCREATORBUG-32854
Change-Id: I02a498ce00fc1afdee900752ade7af6c62b787b7
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>
---
 src/plugins/qmldesigner/designmodewidget.cpp  |  5 +++++
 src/plugins/qmldesigner/designmodewidget.h    |  2 ++
 src/plugins/qmldesigner/qmldesignerplugin.cpp | 11 +++++++++--
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/plugins/qmldesigner/designmodewidget.cpp b/src/plugins/qmldesigner/designmodewidget.cpp
index 34183af8b26..3dea9e15762 100644
--- a/src/plugins/qmldesigner/designmodewidget.cpp
+++ b/src/plugins/qmldesigner/designmodewidget.cpp
@@ -651,6 +651,11 @@ void DesignModeWidget::setMinimumSizeHintFromContentMinimumSize(bool value)
         dockContainer->layout()->update();
 }
 
+bool DesignModeWidget::isInitialized() const
+{
+    return m_initStatus == Initialized;
+}
+
 void DesignModeWidget::dragEnterEvent(QDragEnterEvent *event)
 {
     event->accept();
diff --git a/src/plugins/qmldesigner/designmodewidget.h b/src/plugins/qmldesigner/designmodewidget.h
index 881335da75c..38be692b109 100644
--- a/src/plugins/qmldesigner/designmodewidget.h
+++ b/src/plugins/qmldesigner/designmodewidget.h
@@ -75,6 +75,8 @@ public:
 
     void setMinimumSizeHintFromContentMinimumSize(bool value);
 
+    bool isInitialized() const;
+
 signals:
     void navigationHistoryChanged();
     void initialized();
diff --git a/src/plugins/qmldesigner/qmldesignerplugin.cpp b/src/plugins/qmldesigner/qmldesignerplugin.cpp
index 61dfb8adf45..b0f7c7f0891 100644
--- a/src/plugins/qmldesigner/qmldesignerplugin.cpp
+++ b/src/plugins/qmldesigner/qmldesignerplugin.cpp
@@ -529,8 +529,15 @@ void QmlDesignerPlugin::hideDesigner()
 
 void QmlDesignerPlugin::changeEditor()
 {
-    clearDesigner();
-    setupDesigner();
+    if (d->mainWidget.isInitialized()) {
+        // showDesigner was already already called
+        clearDesigner();
+        setupDesigner();
+    } else {
+        // we are already in Design mode, but showDesigner wasn't called yet,
+        // so we need to call that to set up the widgets
+        showDesigner();
+    }
 }
 
 void QmlDesignerPlugin::jumpTextCursorToSelectedModelNode()