Qt Designer: Add command line option for AA_DisableHighDpiScaling

Pick-to: 5.15
Fixes: QTBUG-83858
Change-Id: Ib0663aa7c98c8f0ae47907f87665c564e5b96186
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>

2 files changed, 20 insertions, 2 deletions

diff --git a/src/designer/src/designer/main.cpp b/src/designer/src/designer/main.cpp
index e5e31ca16..cd428bd4f 100644
--- a/src/designer/src/designer/main.cpp
+++ b/src/designer/src/designer/main.cpp
@@ -34,12 +34,26 @@
 
 QT_USE_NAMESPACE
 
+static bool isOptionSet(int argc, char *argv[], const char *option)
+{
+    for (int i = 1; i < argc; ++i) {
+        if (qstrcmp(argv[i], option) == 0)
+            return true;
+    }
+    return false;
+}
+
 int main(int argc, char *argv[])
 {
     Q_INIT_RESOURCE(designer);
 
-    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
-    QCoreApplication::setAttribute(Qt::AA_UseHighDpiPixmaps);
+    // Attributes to be set before QApplication is constructed.
+    if (isOptionSet(argc, argv, "--no-scaling")) {
+        QCoreApplication::setAttribute(Qt::AA_DisableHighDpiScaling);
+    } else {
+        QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
+        QCoreApplication::setAttribute(Qt::AA_UseHighDpiPixmaps);
+    }
 
     // required for QWebEngineView
     QCoreApplication::setAttribute(Qt::AA_ShareOpenGLContexts);
diff --git a/src/designer/src/designer/qdesigner.cpp b/src/designer/src/designer/qdesigner.cpp
index 4344b1c07..75ab2b01b 100644
--- a/src/designer/src/designer/qdesigner.cpp
+++ b/src/designer/src/designer/qdesigner.cpp
@@ -188,6 +188,10 @@ static inline QDesigner::ParseArgumentsResult
     const QCommandLineOption internalDynamicPropertyOption(QStringLiteral("enableinternaldynamicproperties"),
                                           QStringLiteral("Enable internal dynamic properties"));
     parser.addOption(internalDynamicPropertyOption);
+    const QCommandLineOption noScalingOption(QStringLiteral("no-scaling"),
+                                             QStringLiteral("Disable High DPI scaling"));
+    parser.addOption(noScalingOption);
+
     parser.addPositionalArgument(QStringLiteral("files"),
                                  QStringLiteral("The UI files to open."));