QWindowsTheme::standardPixmap(): Do not create pixmaps with DPR.

The given size is mostly ignored and the resulting pixmaps typically end up
in a QIcon, which will clobber the DPR anyways when returning a pixmap
for a given size.
Moreover, returning a message box icon with a DPR > 1 when
high DPI scaling is active and Qt::AA_UseHighDpiPixmaps is not set
causes the pixmap to become too small due to some scaling error.

Task-number: QTBUG-52622
Change-Id: I8aaaa97667d6c168040e19b7edad9dfb7517f70f
Reviewed-by: Morten Johan Sørvig <morten.sorvig@theqtcompany.com>

src/plugins/platforms/windows/qwindowstheme.cpp

@@ -503,11 +503,8 @@ static QPixmap loadIconFromShell32(int resourceId, QSizeF size)
     return QPixmap();
 }
 
-QPixmap QWindowsTheme::standardPixmap(StandardPixmap sp, const QSizeF &size) const
+QPixmap QWindowsTheme::standardPixmap(StandardPixmap sp, const QSizeF &pixmapSize) const
 {
-    const QScreen *primaryScreen = QGuiApplication::primaryScreen();
-    const int scaleFactor = primaryScreen ? qRound(QHighDpiScaling::factor(primaryScreen)) : 1;
-    const QSizeF pixmapSize = size * scaleFactor;
     int resourceId = -1;
     LPCTSTR iconName = 0;
     switch (sp) {
@@ -577,7 +574,6 @@ QPixmap QWindowsTheme::standardPixmap(StandardPixmap sp, const QSizeF &size) con
             const int iconSize = pixmapSize.width() > 16 ? SHGFI_LARGEICON : SHGFI_SMALLICON;
             if (QWindowsContext::shell32dll.sHGetStockIconInfo(SIID_SHIELD, SHGFI_ICON | iconSize, &iconInfo) == S_OK) {
                 pixmap = qt_pixmapFromWinHICON(iconInfo.hIcon);
-                pixmap.setDevicePixelRatio(scaleFactor);
                 DestroyIcon(iconInfo.hIcon);
                 return pixmap;
             }
@@ -596,7 +592,6 @@ QPixmap QWindowsTheme::standardPixmap(StandardPixmap sp, const QSizeF &size) con
                 QPixmap link = loadIconFromShell32(30, pixmapSize);
                 painter.drawPixmap(0, 0, int(pixmapSize.width()), int(pixmapSize.height()), link);
             }
-            pixmap.setDevicePixelRatio(scaleFactor);
             return pixmap;
         }
     }
@@ -604,13 +599,12 @@ QPixmap QWindowsTheme::standardPixmap(StandardPixmap sp, const QSizeF &size) con
     if (iconName) {
         HICON iconHandle = LoadIcon(NULL, iconName);
         QPixmap pixmap = qt_pixmapFromWinHICON(iconHandle);
-        pixmap.setDevicePixelRatio(scaleFactor);
         DestroyIcon(iconHandle);
         if (!pixmap.isNull())
             return pixmap;
     }
 
-    return QPlatformTheme::standardPixmap(sp, size);
+    return QPlatformTheme::standardPixmap(sp, pixmapSize);
 }
 
 enum { // Shell image list ids