Widget style: Use per-screen DPI in QStyleHelper::dpiScaled()

Pass the style option to dpiScaled() in order to get
the correct screen DPI. The style option contains the
font, which again contains the current DPI value.

Add QFontMetrics::fontDpi() accessors to get the DPI
from the QFont. This DPI will/should be updated on screen
change.

Replace hardcoded Q_OS_MAC DPI with hardcoded base
DPI. This makes per-screen DPI testable on macOS, too.

Task-number: QTBUG-45055
Change-Id: I75f8b37d45eb50c3334b46b8469a546d29712f1b
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

1 files changed, 9 insertions, 7 deletions

diff --git a/src/widgets/dialogs/qwizard_win_p.h b/src/widgets/dialogs/qwizard_win_p.h
index b3796e3f48..2469496b61 100644
--- a/src/widgets/dialogs/qwizard_win_p.h
+++ b/src/widgets/dialogs/qwizard_win_p.h
@@ -108,10 +108,10 @@ public:
     static VistaState vistaState();
     static int titleBarSize() { return QVistaHelper::titleBarSizeDp() / QVistaHelper::m_devicePixelRatio; }
     static int titleBarSizeDp() { return QVistaHelper::frameSizeDp() + QVistaHelper::captionSizeDp(); }
-    static int topPadding() { // padding under text
-        return int(QStyleHelper::dpiScaled(4));
+    static int topPadding(const QPaintDevice *device) { // padding under text
+        return int(QStyleHelper::dpiScaled(4, device));
     }
-    static int topOffset();
+    static int topOffset(const QPaintDevice *device);
 
     static HDC backingStoreDC(const QWidget *wizard, QPoint *offset);
 
@@ -125,10 +125,12 @@ private:
     static int captionSize() { return QVistaHelper::captionSizeDp() / QVistaHelper::m_devicePixelRatio; }
     static int captionSizeDp();
 
-    static int backButtonSize() { return int(QStyleHelper::dpiScaled(30)); }
-    static int iconSize();
-    static int glowSize();
-    int leftMargin() { return backButton_->isVisible() ? backButtonSize() + iconSpacing : 0; }
+    static int backButtonSize(const QPaintDevice *device)
+        { return int(QStyleHelper::dpiScaled(30, device)); }
+    static int iconSize(const QPaintDevice *device);
+    static int glowSize(const QPaintDevice *device);
+    int leftMargin(const QPaintDevice *device)
+        { return backButton_->isVisible() ? backButtonSize(device) + iconSpacing : 0; }
 
     int titleOffset();
     void drawTitleBar(QPainter *painter);