QWindowsTheme: Fix the available file icon sizes

Previously, QWindowsTheme had a hardcoded list of of available file icon sizes.
As the sizes depend on the Windows display scale factor, this can lead to
undesired scaling of icons.

Maintain an array of the standard sizes against which the sizes are
matched; refresh in display change.

Task-number: QTBUG-54561
Change-Id: If36de2f30c8a230cc7bd8eeb4dfc9f201aeda5e4
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>

src/plugins/platforms/windows/qwindowscontext.cpp

@@ -41,6 +41,7 @@
 #include "qwindowsmime.h"
 #include "qwindowsinputcontext.h"
 #include "qwindowstabletsupport.h"
+#include "qwindowstheme.h"
 #include <private/qguiapplication_p.h>
 #ifndef QT_NO_ACCESSIBILITY
 # include "accessible/qwindowsaccessibility.h"
@@ -1007,6 +1008,8 @@ bool QWindowsContext::windowsProc(HWND hwnd, UINT message,
 #endif
     case QtWindows::DisplayChangedEvent:
         return d->m_screenManager.handleDisplayChange(wParam, lParam);
+        if (QWindowsTheme *t = QWindowsTheme::instance())
+            t->displayChanged();
     case QtWindows::SettingChangedEvent:
         return d->m_screenManager.handleScreenChanges();
     default:

src/plugins/platforms/windows/qwindowstheme.cpp

@@ -329,6 +329,7 @@ QWindowsTheme::QWindowsTheme()
     std::fill(m_fonts, m_fonts + NFonts, static_cast<QFont *>(0));
     std::fill(m_palettes, m_palettes + NPalettes, static_cast<QPalette *>(0));
     refresh();
+    refreshIconPixmapSizes();
 }
 
 QWindowsTheme::~QWindowsTheme()
@@ -394,16 +395,8 @@ QVariant QWindowsTheme::themeHint(ThemeHint hint) const
         return QVariant(int(WindowsKeyboardScheme));
     case UiEffects:
         return QVariant(uiEffects());
-    case IconPixmapSizes: {
-        QList<int> sizes;
-        sizes << 16 << 32;
-#ifdef USE_IIMAGELIST
-        sizes << 48; // sHIL_EXTRALARGE
-        if (QSysInfo::WindowsVersion >= QSysInfo::WV_VISTA)
-            sizes << 256; // SHIL_JUMBO
-#endif // USE_IIMAGELIST
-        return QVariant::fromValue(sizes);
-    }
+    case IconPixmapSizes:
+        return m_fileIconSizes;
     case DialogSnapToDefaultButton:
         return QVariant(booleanSystemParametersInfo(SPI_GETSNAPTODEFBUTTON, false));
     case ContextMenuOnMouseRelease:
@@ -473,6 +466,15 @@ void QWindowsTheme::refreshFonts()
 #endif // !Q_OS_WINCE
 }
 
+enum FileIconSize {
+    // Standard icons obtainable via shGetFileInfo(), SHGFI_SMALLICON, SHGFI_LARGEICON
+    SmallFileIcon, LargeFileIcon,
+    // Larger icons obtainable via SHGetImageList()
+    ExtraLargeFileIcon,
+    JumboFileIcon, // Vista onwards
+    FileIconSizeCount
+};
+
 bool QWindowsTheme::usePlatformNativeDialog(DialogType type) const
 {
     return QWindowsDialogs::useHelper(type);
@@ -489,6 +491,27 @@ void QWindowsTheme::windowsThemeChanged(QWindow * window)
     QWindowSystemInterface::handleThemeChange(window);
 }
 
+static int fileIconSizes[FileIconSizeCount];
+
+void QWindowsTheme::refreshIconPixmapSizes()
+{
+    // Standard sizes: 16, 32, 48, 256
+    fileIconSizes[SmallFileIcon] = GetSystemMetrics(SM_CXSMICON); // corresponds to SHGFI_SMALLICON);
+    fileIconSizes[LargeFileIcon] = GetSystemMetrics(SM_CXICON); // corresponds to SHGFI_LARGEICON
+    fileIconSizes[ExtraLargeFileIcon] =
+        fileIconSizes[LargeFileIcon] + fileIconSizes[LargeFileIcon] / 2;
+    fileIconSizes[JumboFileIcon] = 8 * fileIconSizes[LargeFileIcon]; // empirical, has not been observed to work
+    QList<int> sizes;
+    sizes << fileIconSizes[SmallFileIcon] << fileIconSizes[LargeFileIcon];
+#ifdef USE_IIMAGELIST
+    sizes << fileIconSizes[ExtraLargeFileIcon]; // sHIL_EXTRALARGE
+    if (QSysInfo::WindowsVersion >= QSysInfo::WV_VISTA)
+        sizes << fileIconSizes[JumboFileIcon]; // SHIL_JUMBO
+#endif // USE_IIMAGELIST
+    qCDebug(lcQpaWindows) << __FUNCTION__ << sizes;
+    m_fileIconSizes = QVariant::fromValue(sizes);
+}
+
 // Defined in qpixmap_win.cpp
 Q_GUI_EXPORT QPixmap qt_pixmapFromWinHICON(HICON icon);
 
@@ -706,10 +729,12 @@ QPixmap QWindowsTheme::fileIconPixmap(const QFileInfo &fileInfo, const QSizeF &s
     QPixmap pixmap;
     const QString filePath = QDir::toNativeSeparators(fileInfo.filePath());
     const int width = int(size.width());
-    const int iconSize = width > 16 ? SHGFI_LARGEICON : SHGFI_SMALLICON;
+    const int iconSize = width > fileIconSizes[SmallFileIcon] ? SHGFI_LARGEICON : SHGFI_SMALLICON;
     const int requestedImageListSize =
 #ifdef USE_IIMAGELIST
-        width > 48 ? sHIL_JUMBO : (width > 32 ? sHIL_EXTRALARGE : 0);
+        width > fileIconSizes[ExtraLargeFileIcon]
+            ? sHIL_JUMBO
+            : (width > fileIconSizes[LargeFileIcon] ? sHIL_EXTRALARGE : 0);
 #else
         0;
 #endif // !USE_IIMAGELIST

src/plugins/platforms/windows/qwindowstheme.h

@@ -37,6 +37,8 @@
 #include "qwindowsthreadpoolrunner.h"
 #include <qpa/qplatformtheme.h>
 
+#include <QtCore/QVariant>
+
 QT_BEGIN_NAMESPACE
 
 class QWindow;
@@ -62,6 +64,7 @@ public:
                            QPlatformTheme::IconOptions iconOptions = 0) const Q_DECL_OVERRIDE;
 
     void windowsThemeChanged(QWindow *window);
+    void displayChanged() { refreshIconPixmapSizes(); }
 
     static const char *name;
 
@@ -71,11 +74,13 @@ private:
     void refreshPalettes();
     void clearFonts();
     void refreshFonts();
+    void refreshIconPixmapSizes();
 
     static QWindowsTheme *m_instance;
     QPalette *m_palettes[NPalettes];
     QFont *m_fonts[NFonts];
     mutable QWindowsThreadPoolRunner m_threadPoolRunner;
+    QVariant m_fileIconSizes;
 };
 
 QT_END_NAMESPACE