Document that QPlatformTheme::standardPixmap should always be a 1x pixmap

This reverts 59bbfb17db563d7e62b9f3158dab3cc6e7e68acd and
c853054910552f5fef04797222dde0d29a0c340d, as that approach
was causing issues for QCommonStyle::iconFromWindowsTheme,
for example in situations where the system has a 1x and 2.5x
screen, and the user requests a 16x16 pixmap or icon via
QStyle::standardPixmap or QStyle::standardIcon. In that
situation our smallest pixmap is 40x40, and we need to
downscale, causing blurred results on a 1x screen.

Pick-to: 6.9
Change-Id: Ifa6e15d37d15954df689253c32eaa779885c567b
Reviewed-by: Volker Hilsheimer <[email protected]>

4 files changed, 18 insertions, 17 deletions

diff --git a/src/gui/kernel/qplatformtheme.cpp b/src/gui/kernel/qplatformtheme.cpp
index c38ca70eb60..aa530c5f08c 100644
--- a/src/gui/kernel/qplatformtheme.cpp
+++ b/src/gui/kernel/qplatformtheme.cpp
@@ -470,9 +470,16 @@ const QFont *QPlatformTheme::font(Font type) const
     return nullptr;
 }
 
-QPixmap QPlatformTheme::standardPixmap(StandardPixmap sp, const QSizeF &size) const
+/*!
+    \brief Return a pixmap for \a standardPixmap, at the given \a size.
+
+    The implementation should not take system DPR into account, and
+    always return a pixmap with a DPR of 1. It's up to the consumer
+    to account for DPR and request a pixmap of the right size.
+*/
+QPixmap QPlatformTheme::standardPixmap(StandardPixmap standardPixmap, const QSizeF &size) const
 {
-    Q_UNUSED(sp);
+    Q_UNUSED(standardPixmap);
     Q_UNUSED(size);
     // TODO Should return QCommonStyle pixmaps?
     return QPixmap();
diff --git a/src/plugins/platforms/cocoa/qcocoatheme.mm b/src/plugins/platforms/cocoa/qcocoatheme.mm
index 022ef8f072f..6d15e8e5d2c 100644
--- a/src/plugins/platforms/cocoa/qcocoatheme.mm
+++ b/src/plugins/platforms/cocoa/qcocoatheme.mm
@@ -390,9 +390,7 @@ QPixmap QCocoaTheme::standardPixmap(StandardPixmap sp, const QSizeF &size) const
         QT_IGNORE_DEPRECATIONS(GetIconRef(kOnSystemDisk, kSystemIconsCreator, iconType, &icon));
 
         if (icon) {
-            const auto dpr = qGuiApp->devicePixelRatio(); // Highest in the system
-            pixmap = qt_mac_convert_iconref(icon, size.width() * dpr, size.height() * dpr);
-            pixmap.setDevicePixelRatio(dpr);
+            pixmap = qt_mac_convert_iconref(icon, size.width(), size.height());
             QT_IGNORE_DEPRECATIONS(ReleaseIconRef(icon));
         }
 
diff --git a/src/plugins/platforms/windows/qwindowstheme.cpp b/src/plugins/platforms/windows/qwindowstheme.cpp
index 92b8478ee52..1379018793b 100644
--- a/src/plugins/platforms/windows/qwindowstheme.cpp
+++ b/src/plugins/platforms/windows/qwindowstheme.cpp
@@ -803,12 +803,12 @@ void QWindowsTheme::refreshIconPixmapSizes()
 // Defined in qpixmap_win.cpp
 Q_GUI_EXPORT QPixmap qt_pixmapFromWinHICON(HICON icon);
 
-static QPixmap loadIconFromShell32(int resourceId, QSize size)
+static QPixmap loadIconFromShell32(int resourceId, QSizeF size)
 {
     if (const HMODULE hmod = QSystemLibrary::load(L"shell32")) {
         auto iconHandle =
             static_cast<HICON>(LoadImage(hmod, MAKEINTRESOURCE(resourceId),
-                                         IMAGE_ICON, size.width(), size.height(), 0));
+                                         IMAGE_ICON, int(size.width()), int(size.height()), 0));
         if (iconHandle) {
             QPixmap iconpixmap = qt_pixmapFromWinHICON(iconHandle);
             DestroyIcon(iconHandle);
@@ -818,7 +818,7 @@ static QPixmap loadIconFromShell32(int resourceId, QSize size)
     return QPixmap();
 }
 
-QPixmap QWindowsTheme::standardPixmap(StandardPixmap sp, const QSizeF &size) const
+QPixmap QWindowsTheme::standardPixmap(StandardPixmap sp, const QSizeF &pixmapSize) const
 {
     int resourceId = -1;
     SHSTOCKICONID stockId = SIID_INVALID;
@@ -907,19 +907,16 @@ QPixmap QWindowsTheme::standardPixmap(StandardPixmap sp, const QSizeF &size) con
         break;
     }
 
-    const auto dpr = qGuiApp->devicePixelRatio(); // Highest in the system
-
     if (stockId != SIID_INVALID) {
         SHSTOCKICONINFO iconInfo;
         memset(&iconInfo, 0, sizeof(iconInfo));
         iconInfo.cbSize = sizeof(iconInfo);
         stockFlags |= SHGSI_ICONLOCATION;
         if (SHGetStockIconInfo(stockId, stockFlags, &iconInfo) == S_OK) {
-            const auto iconSize = size.width() * dpr;
+            const auto iconSize = pixmapSize.width();
             HICON icon;
             if (SHDefExtractIcon(iconInfo.szPath, iconInfo.iIcon, 0, &icon, nullptr, iconSize) == S_OK) {
                 QPixmap pixmap = qt_pixmapFromWinHICON(icon);
-                pixmap.setDevicePixelRatio(dpr);
                 DestroyIcon(icon);
                 return pixmap;
             }
@@ -927,15 +924,13 @@ QPixmap QWindowsTheme::standardPixmap(StandardPixmap sp, const QSizeF &size) con
     }
 
     if (resourceId != -1) {
-        const QSize pixmapSize(size.width() * dpr, size.height() * dpr);
         QPixmap pixmap = loadIconFromShell32(resourceId, pixmapSize);
         if (!pixmap.isNull()) {
             if (sp == FileLinkIcon || sp == DirLinkIcon || sp == DirLinkOpenIcon) {
                 QPainter painter(&pixmap);
                 QPixmap link = loadIconFromShell32(30, pixmapSize);
-                painter.drawPixmap(0, 0, pixmapSize.width(), pixmapSize.height(), link);
+                painter.drawPixmap(0, 0, int(pixmapSize.width()), int(pixmapSize.height()), link);
             }
-            pixmap.setDevicePixelRatio(dpr);
             return pixmap;
         }
     }
@@ -948,7 +943,7 @@ QPixmap QWindowsTheme::standardPixmap(StandardPixmap sp, const QSizeF &size) con
             return pixmap;
     }
 
-    return QPlatformTheme::standardPixmap(sp, size);
+    return QPlatformTheme::standardPixmap(sp, pixmapSize);
 }
 
 enum { // Shell image list ids
diff --git a/tests/manual/iconbrowser/main.cpp b/tests/manual/iconbrowser/main.cpp
index c22dcbf7113..11968d86eb7 100644
--- a/tests/manual/iconbrowser/main.cpp
+++ b/tests/manual/iconbrowser/main.cpp
@@ -413,7 +413,8 @@ public:
             case Theme:
                 if (row >= themedIcons.size())
                     break;
-                return QIcon(QApplicationPrivate::platformTheme()->standardPixmap(QPlatformTheme::StandardPixmap(row), {64, 64}));
+                return QIcon(QApplicationPrivate::platformTheme()->standardPixmap(
+                    QPlatformTheme::StandardPixmap(row), QSize(64, 64) * qGuiApp->devicePixelRatio()));
             case Icon:
                 if (row < themedIcons.size())
                     return QIcon::fromTheme(themedIcons.at(row));