StyleSheetStyle: Load @Nx images

Perform a @Nx image file lookup when loading pixmaps.

Make drawBackgroundImage() handle high-dpi pixmaps,
here the layout calculations needs to be in device-
independent pixels

Fixes: QTBUG-36825
Change-Id: I61e6f53c59f61f3bd88c34a036349e51e8c8ad92
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>
Reviewed-by: Alex Blasche <alexander.blasche@qt.io>

src/widgets/styles/qstylesheetstyle.cpp

@@ -115,6 +115,8 @@
 #include <QtWidgets/qtoolbar.h>
 #endif
 
+#include <QtGui/qscreen.h>
+
 QT_BEGIN_NAMESPACE
 
 using namespace QCss;
@@ -952,8 +954,10 @@ QRenderRule::QRenderRule(const QVector<Declaration> &declarations, const QObject
     Attachment attachment = Attachment_Scroll;
     origin = Origin_Padding;
     Origin clip = Origin_Border;
-    if (v.extractBackground(&brush, &uri, &repeat, &alignment, &origin, &attachment, &clip))
+    if (v.extractBackground(&brush, &uri, &repeat, &alignment, &origin, &attachment, &clip)) {
-        bg = new QStyleSheetBackgroundData(brush, QPixmap(uri), repeat, alignment, origin, attachment, clip);
+        bg = new QStyleSheetBackgroundData(brush, QStyleSheetStyle::loadPixmap(uri, object),
+                                           repeat, alignment, origin, attachment, clip);
+    }
 
     QBrush sfg, fg;
     QBrush sbg, abg;
@@ -992,7 +996,7 @@ QRenderRule::QRenderRule(const QVector<Declaration> &declarations, const QObject
                     bd->bi = new QStyleSheetBorderImageData;
 
                 QStyleSheetBorderImageData *bi = bd->bi;
-                bi->pixmap = QPixmap(uri);
+                bi->pixmap = QStyleSheetStyle::loadPixmap(uri, object);
                 for (int i = 0; i < 4; i++)
                     bi->cuts[i] = cuts[i];
                 bi->horizStretch = horizStretch;
@@ -1215,30 +1219,33 @@ void QRenderRule::drawBackgroundImage(QPainter *p, const QRect &rect, QPoint off
     if (background()->attachment == Attachment_Fixed)
         off = QPoint(0, 0);
 
+    QSize bgpSize = bgp.size() / bgp.devicePixelRatio();
+    int bgpHeight = bgpSize.height();
+    int bgpWidth = bgpSize.width();
     QRect r = originRect(rect, background()->origin);
-    QRect aligned = QStyle::alignedRect(Qt::LeftToRight, background()->position, bgp.size(), r);
+    QRect aligned = QStyle::alignedRect(Qt::LeftToRight, background()->position, bgpSize, r);
     QRect inter = aligned.translated(-off).intersected(r);
 
     switch (background()->repeat) {
     case Repeat_Y:
         p->drawTiledPixmap(inter.x(), r.y(), inter.width(), r.height(), bgp,
                            inter.x() - aligned.x() + off.x(),
-                           bgp.height() - int(aligned.y() - r.y()) % bgp.height() + off.y());
+                           bgpHeight - int(aligned.y() - r.y()) % bgpHeight + off.y());
         break;
     case Repeat_X:
         p->drawTiledPixmap(r.x(), inter.y(), r.width(), inter.height(), bgp,
-                           bgp.width() - int(aligned.x() - r.x())%bgp.width() + off.x(),
+                           bgpWidth - int(aligned.x() - r.x())%bgpWidth + off.x(),
                            inter.y() - aligned.y() + off.y());
         break;
     case Repeat_XY:
         p->drawTiledPixmap(r, bgp,
-                           QPoint(bgp.width() - int(aligned.x() - r.x())% bgp.width() + off.x(),
+                            QPoint(bgpWidth - int(aligned.x() - r.x())% bgpWidth + off.x(),
-                                  bgp.height() - int(aligned.y() - r.y())%bgp.height() + off.y()));
+                                   bgpHeight - int(aligned.y() - r.y())%bgpHeight + off.y()));
         break;
     case Repeat_None:
     default:
         p->drawPixmap(inter.x(), inter.y(), bgp, inter.x() - aligned.x() + off.x(),
-                      inter.y() - aligned.y() + off.y(), inter.width(), inter.height());
+                      inter.y() - aligned.y() + off.y(), bgp.width() , bgp.height());
         break;
     }
 
@@ -6107,6 +6114,28 @@ bool QStyleSheetStyle::isNaturalChild(const QObject *obj)
     return false;
 }
 
+QPixmap QStyleSheetStyle::loadPixmap(const QString &fileName, const QObject *context)
+{
+    qreal ratio = -1.0;
+    if (const QWidget *widget = qobject_cast<const QWidget *>(context)) {
+        if (QScreen *screen = QApplication::screenAt(widget->mapToGlobal(QPoint(0, 0))))
+            ratio = screen->devicePixelRatio();
+    }
+
+    if (ratio < 0) {
+        if (const QApplication *app = qApp)
+            ratio = app->devicePixelRatio();
+        else
+            ratio = 1.0;
+    }
+
+    qreal sourceDevicePixelRatio = 1.0;
+    QString resolvedFileName = qt_findAtNxFile(fileName, ratio, &sourceDevicePixelRatio);
+    QPixmap pixmap(resolvedFileName);
+    pixmap.setDevicePixelRatio(sourceDevicePixelRatio);
+    return pixmap;
+}
+
 QT_END_NAMESPACE
 
 #include "moc_qstylesheetstyle_p.cpp"

src/widgets/styles/qstylesheetstyle_p.h

@@ -167,6 +167,7 @@ private:
 
     static Qt::Alignment resolveAlignment(Qt::LayoutDirection, Qt::Alignment);
     static bool isNaturalChild(const QObject *obj);
+    static QPixmap loadPixmap(const QString &fileName, const QObject *context);
     bool initObject(const QObject *obj) const;
 public:
     static int numinstances;

tests/auto/widgets/styles/qstylesheetstyle/resources.qrc

@@ -2,5 +2,6 @@
 <RCC version="1.0">
   <qresource>
     <file>images/testimage.png</file>
+    <file>images/testimage@2x.png</file>
   </qresource>
 </RCC>

tests/auto/widgets/styles/qstylesheetstyle/tst_qstylesheetstyle.cpp

@@ -33,6 +33,7 @@
 #include <QMetaObject>
 
 #include <private/qstylesheetstyle_p.h>
+#include <private/qhighdpiscaling_p.h>
 #include <QtTest/private/qtesthelpers_p.h>
 
 using namespace QTestPrivate;
@@ -101,6 +102,9 @@ private slots:
     void styleSheetTargetAttribute();
     void unpolish();
 
+    void highdpiImages_data();
+    void highdpiImages();
+
 private:
     QColor COLOR(const QWidget& w) {
         w.ensurePolished();
@@ -2066,6 +2070,35 @@ void tst_QStyleSheetStyle::unpolish()
     QCOMPARE(w.minimumWidth(), 0);
 }
 
+void tst_QStyleSheetStyle::highdpiImages_data()
+{
+    QTest::addColumn<qreal>("screenFactor");
+    QTest::addColumn<QColor>("color");
+
+    QTest::newRow("highdpi") << 2.0 << QColor(0x00, 0xFF, 0x00);
+    QTest::newRow("lowdpi")  << 1.0 << QColor(0xFF, 0x00, 0x00);
+}
+
+void tst_QStyleSheetStyle::highdpiImages()
+{
+    QFETCH(qreal, screenFactor);
+    QFETCH(QColor, color);
+
+    QWidget w;
+    QScreen *screen = QGuiApplication::screenAt(w.pos());
+    QHighDpiScaling::setScreenFactor(screen, screenFactor);
+    w.setStyleSheet("QWidget { background-image: url(\":/images/testimage.png\"); }");
+    w.show();
+
+    QVERIFY(QTest::qWaitForWindowExposed(&w));
+    QImage image(w.size(), QImage::Format_ARGB32);
+    w.render(&image);
+    QVERIFY(testForColors(image, color));
+
+    QHighDpiScaling::setScreenFactor(screen, 1.0);
+    QHighDpiScaling::updateHighDpiScaling(); // reset to normal
+}
+
 QTEST_MAIN(tst_QStyleSheetStyle)
 #include "tst_qstylesheetstyle.moc"