Qt GUI theme looks old-fashioned

Question

When I cross-compile Qt 5.8.0 from source myself and use it to build the Qt \"Dynamic Layouts\" example from Qt Widgets for Microsoft Windows, it looks old-fashioned, as if it w

Answer 1

If you look in the src/widgets/configure.json file from Qt 5.8.0, you can see that it checks for the existence of uxtheme.h, and that uxtheme.h is a precondition for compiling the windowsxp style, which is a precondition for compiling the windowsvista style. By looking in Qt's config.log, I saw that the uxtheme.h test failed. I am not sure why, but it's probably because uxtheme.h cannot be included on its own; you need to include windows.h beforehand. I verified that the windowsxp and windowsvista styles were indeed not enabled by looking in the src/widgets/qtwidgets-config.pri file after configuring Qt. It has a list of styles that are going to get compiled, and windowsvista is not the list.

I tried adding the -style-windowsxp -style-windowsvista options to Qt's configure command, but those options just cause errors because the uxtheme.h test is failing and it is a prerequisite for compiling those themes.

My solution was to apply this patch to Qt 5.8.0 to skip the uxtheme test altogether:

diff -ur qt58-orig/src/widgets/configure.json qt58/src/widgets/configure.json
--- qt58-orig/src/widgets/configure.json        2017-05-28 02:07:07.625626151 -0700
+++ qt58/src/widgets/configure.json     2017-06-27 21:25:52.752628339 -0700
@@ -28,11 +28,6 @@
     },

     "tests": {
-        "uxtheme": {
-            "label": "uxtheme.h",
-            "type": "files",
-            "files": [ "uxtheme.h" ]
-        }
     },

     "features": {
@@ -57,7 +52,7 @@
         },
         "style-windowsxp": {
             "label": "WindowsXP",
-            "condition": "features.style-windows && config.win32 && !config.winrt && tests.uxtheme",
+            "condition": "features.style-windows && config.win32 && !config.winrt",
             "output": [ "styles" ]
         },
         "style-windowsvista": {

I'm not sure why the MSYS2 package worked well, since I don't see any patch like this in their build script.

Answer 2

Widgets

Qt-based GUIs will automatically select the default theme depending on your OS. If you want to override it, you are looking for QApplication's setStyle method, which lets you define the style used for your application, regardless of the OS it runs on.

QApplication::setStyle("fusion");

From the documentation, the following are supported:

• "windows"
• "fusion"
• "windowsxp"
• "macintosh"

The supported themes depend on your platform, and can be extended with plugins.

---

EDIT: This answer targets situations where the OS is correctly detected by Qt configuration step, and you just want to change the theme used. In the situation described, the incorrect theme was selected, which is fixed in OP's answer.

Qt Quick

If your GUI is based on QtQuick instead of Widgets, you can use QQuickStyle::setStyle("Material"); instead to customize the theme that you want to see used.

For more details, you can look at that documentation page:

• https://doc.qt.io/qt-5/qtquickcontrols2-styles.html#using-styles-in-qt-quick-controls-2

Answer 3

I had this same issue when upgrading from a static Qt 5.6.3 to static 5.12.0. I solved it after I tried to manually set the "windowsvista" style with QApplication::setStyle() and noticed that it returned null when debugging. It turns out in 5.12.0 the windowsvista style is its own separate plugin and you need to link against plugins/styles/qwindowsvistastyle.lib and add Q_IMPORT_PLUGIN(QWindowsVistaStylePlugin) to the cpp file containing your main function. After that there is no need to manually set the style, it is chosen automatically.

Answer 4

I had the same issue after upgrading from Qt5.9.1 to Qt5.12.

Placing qwindowsvistastyle.dll, which I found to be in Qt\5.12.0\msvc2017_64\plugins\styles, needed to be placed in my applicationDir\styles directory.