QWindowsTheme: honor dpr when requesting standard icons

The devicePixelRatio was not taken into account when a standard icon was
requested from the windows qpa which resulted in blurry icons for a
dpr != 1.
Therefore pass the dpr-corrected size to QWindowsTheme::standardPixmap()
and pass this size to SHDefExtractIcon() to get a correctly scaled icon.

Pick-to: 6.7 6.6
Fixes: QTBUG-52622
Change-Id: Ia771dd2f93fa133cf2c4429ef59a9c5cb05ad047
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

2 files changed, 18 insertions, 10 deletions

diff --git a/src/plugins/platforms/windows/qwindowstheme.cpp b/src/plugins/platforms/windows/qwindowstheme.cpp
index 62ed4da548..447973a133 100644
--- a/src/plugins/platforms/windows/qwindowstheme.cpp
+++ b/src/plugins/platforms/windows/qwindowstheme.cpp
@@ -931,15 +931,18 @@ QPixmap QWindowsTheme::standardPixmap(StandardPixmap sp, const QSizeF &pixmapSiz
     }
 
     if (stockId != SIID_INVALID) {
-        QPixmap pixmap;
         SHSTOCKICONINFO iconInfo;
         memset(&iconInfo, 0, sizeof(iconInfo));
         iconInfo.cbSize = sizeof(iconInfo);
-        stockFlags |= (pixmapSize.width() > 16 ? SHGFI_LARGEICON : SHGFI_SMALLICON);
-        if (SHGetStockIconInfo(stockId, SHGFI_ICON | stockFlags, &iconInfo) == S_OK) {
-            pixmap = qt_pixmapFromWinHICON(iconInfo.hIcon);
-            DestroyIcon(iconInfo.hIcon);
-            return pixmap;
+        stockFlags |= SHGSI_ICONLOCATION;
+        if (SHGetStockIconInfo(stockId, stockFlags, &iconInfo) == S_OK) {
+            const auto iconSize = pixmapSize.width();
+            HICON icon;
+            if (SHDefExtractIcon(iconInfo.szPath, iconInfo.iIcon, 0, &icon, nullptr, iconSize) == S_OK) {
+                QPixmap pixmap = qt_pixmapFromWinHICON(icon);
+                DestroyIcon(icon);
+                return pixmap;
+            }
         }
     }
 
diff --git a/src/widgets/styles/qcommonstyle.cpp b/src/widgets/styles/qcommonstyle.cpp
index 106536cb02..57d823171f 100644
--- a/src/widgets/styles/qcommonstyle.cpp
+++ b/src/widgets/styles/qcommonstyle.cpp
@@ -5616,8 +5616,10 @@ QIcon QCommonStylePrivate::iconFromWindowsTheme(QCommonStyle::StandardPixmap sta
     case QStyle::SP_MessageBoxQuestion:
         if (const QPlatformTheme *theme = QGuiApplicationPrivate::platformTheme()) {
             QPlatformTheme::StandardPixmap sp = static_cast<QPlatformTheme::StandardPixmap>(standardIcon);
-            for (int size = 16 ; size <= 32 ; size += 16) {
-                QPixmap pixmap = theme->standardPixmap(sp, QSizeF(size, size));
+            const auto dpr = qt_getDevicePixelRatio(widget);
+            for (const int size : {16, 32}) {
+                QPixmap pixmap = theme->standardPixmap(sp, QSizeF(size, size) * dpr);
+                pixmap.setDevicePixelRatio(dpr);
                 icon.addPixmap(pixmap, QIcon::Normal);
             }
         }
@@ -5628,11 +5630,14 @@ QIcon QCommonStylePrivate::iconFromWindowsTheme(QCommonStyle::StandardPixmap sta
             QPlatformTheme::StandardPixmap spOff = static_cast<QPlatformTheme::StandardPixmap>(standardIcon);
             QPlatformTheme::StandardPixmap spOn = standardIcon == QStyle::SP_DirIcon ? QPlatformTheme::DirOpenIcon
                                                                                      : QPlatformTheme::DirLinkOpenIcon;
-            for (int size = 16 ; size <= 32 ; size += 16) {
-                QSizeF pixSize(size, size);
+            const auto dpr = qt_getDevicePixelRatio(widget);
+            for (const int size : {16, 32}) {
+                const QSizeF pixSize = QSizeF(size, size) * dpr;
                 QPixmap pixmap = theme->standardPixmap(spOff, pixSize);
+                pixmap.setDevicePixelRatio(dpr);
                 icon.addPixmap(pixmap, QIcon::Normal, QIcon::Off);
                 pixmap = theme->standardPixmap(spOn, pixSize);
+                pixmap.setDevicePixelRatio(dpr);
                 icon.addPixmap(pixmap, QIcon::Normal, QIcon::On);
             }
         }