Gui: Respect both content size and minimum width for buttons

This is a hacky fix for https://github.com/FreeCAD/FreeCAD/issues/23607

Basically after widget is shown or polished we enforce it's minimum size to at
least cover the minimum size hint - something that QSS ignores if min-width is
specified.

src/Gui/Application.cpp

@@ -39,6 +39,7 @@
 #include <QTextStream>
 #include <QTimer>
 #include <QWindow>
+#include <QStyleFactory>
 
 #include <QLoggingCategory>
 #include <fmt/format.h>
@@ -141,6 +142,7 @@
 #include "Inventor/SoFCPlacementIndicatorKit.h"
 #include "QtWidgets.h"
 
+#include <FreeCADStyle.h>
 #include <OverlayManager.h>
 #include <ParamHandler.h>
 #include <Base/ServiceProvider.h>
@@ -2768,6 +2770,38 @@ QString Application::replaceVariablesInQss(const QString& qssText)
     return QString::fromStdString(d->styleParameterManager->replacePlaceholders(qssText.toStdString()));
 }
 
+void Application::setStyle(const QString& name)
+{
+    const auto createStyleFromName = [](const QString& name) -> QStyle* {
+        if (name == "FreeCAD") {
+            return new FreeCADStyle();
+        }
+
+        if (name.compare("System", Qt::CaseInsensitive) == 0) {
+            return nullptr;
+        }
+
+        return QStyleFactory::create(name);
+    };
+
+    const auto requiresEventFilter = [](QStyle* style) {
+        // for now only FreeCAD style requires additional event processing
+        return qobject_cast<FreeCADStyle*>(style) != nullptr;
+    };
+
+    if (auto* current = qApp->style(); current != nullptr && requiresEventFilter(current)) {
+        qApp->removeEventFilter(current);
+    }
+
+    if (auto* style = createStyleFromName(name)) {
+        qApp->setStyle(style);
+
+        if (requiresEventFilter(style)) {
+            qApp->installEventFilter(style);
+        }
+    }
+}
+
 void Application::checkForDeprecatedSettings()
 {
     // From 0.21, `FCBak` will be the intended default backup format