Windows QPA: Fix blank Cursor on secondary display

CreateCursor only works with standard sizes (32, ...) depending on the
display hardware. No longer apply the scale factor for the blank cursor, because
it might lead to unsupported cursor sizes resulting in random pixels.

Change-Id: I48d84bd913d2dd8f62129126c9a41e58ee2cbcae
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

1 files changed, 12 insertions, 10 deletions

diff --git a/src/plugins/platforms/windows/qwindowscursor.cpp b/src/plugins/platforms/windows/qwindowscursor.cpp
index 00d011ccec..20a8117304 100644
--- a/src/plugins/platforms/windows/qwindowscursor.cpp
+++ b/src/plugins/platforms/windows/qwindowscursor.cpp
@@ -184,9 +184,11 @@ static HCURSOR createBitmapCursor(const QCursor &cursor, qreal scaleFactor = 1)
     return createBitmapCursor(bbits, mbits, cursor.hotSpot(), invb, invm);
 }
 
-static QSize systemCursorSize(const QPlatformScreen *screen = nullptr)
+static QSize systemCursorSize() { return QSize(GetSystemMetrics(SM_CXCURSOR), GetSystemMetrics(SM_CYCURSOR)); }
+
+static QSize screenCursorSize(const QPlatformScreen *screen = nullptr)
 {
-    const QSize primaryScreenCursorSize(GetSystemMetrics(SM_CXCURSOR), GetSystemMetrics(SM_CYCURSOR));
+    const QSize primaryScreenCursorSize = systemCursorSize();
     if (screen) {
         // Correct the size if the DPI value of the screen differs from
         // that of the primary screen.
@@ -212,7 +214,7 @@ static inline QSize standardCursorSize() { return QSize(32, 32); }
 // createBitmapCursor() only work for standard sizes (32,48,64...), which does
 // not work when scaling the 16x16 openhand cursor bitmaps to 150% (resulting
 // in a non-standard 24x24 size).
-static QWindowsCursor::PixmapCursor createPixmapCursorFromData(const QSize &systemCursorSize,
+static QWindowsCursor::PixmapCursor createPixmapCursorFromData(const QSize &screenCursorSize,
                                           // The cursor size the bitmap is targeted for
                                           const QSize &bitmapTargetCursorSize,
                                           // The actual size of the bitmap data
@@ -222,7 +224,7 @@ static QWindowsCursor::PixmapCursor createPixmapCursorFromData(const QSize &syst
     QPixmap rawImage = QPixmap::fromImage(QBitmap::fromData(QSize(bitmapSize, bitmapSize), bits).toImage());
     rawImage.setMask(QBitmap::fromData(QSize(bitmapSize, bitmapSize), maskBits));
 
-    const qreal factor = qreal(systemCursorSize.width()) / qreal(bitmapTargetCursorSize.width());
+    const qreal factor = qreal(screenCursorSize.width()) / qreal(bitmapTargetCursorSize.width());
     // Scale images if the cursor size is significantly different, starting with 150% where the system cursor
     // size is 48.
     if (qAbs(factor - 1.0) > 0.4) {
@@ -402,13 +404,13 @@ QWindowsCursor::PixmapCursor QWindowsCursor::customCursor(Qt::CursorShape cursor
 
     switch (cursorShape) {
     case Qt::SplitVCursor:
-        return createPixmapCursorFromData(systemCursorSize(screen), standardCursorSize(), 32, vsplit_bits, vsplitm_bits);
+        return createPixmapCursorFromData(screenCursorSize(screen), standardCursorSize(), 32, vsplit_bits, vsplitm_bits);
     case Qt::SplitHCursor:
-        return createPixmapCursorFromData(systemCursorSize(screen), standardCursorSize(), 32, hsplit_bits, hsplitm_bits);
+        return createPixmapCursorFromData(screenCursorSize(screen), standardCursorSize(), 32, hsplit_bits, hsplitm_bits);
     case Qt::OpenHandCursor:
-        return createPixmapCursorFromData(systemCursorSize(screen), standardCursorSize(), 16, openhand_bits, openhandm_bits);
+        return createPixmapCursorFromData(screenCursorSize(screen), standardCursorSize(), 16, openhand_bits, openhandm_bits);
     case Qt::ClosedHandCursor:
-        return createPixmapCursorFromData(systemCursorSize(screen), standardCursorSize(), 16, closedhand_bits, closedhandm_bits);
+        return createPixmapCursorFromData(screenCursorSize(screen), standardCursorSize(), 16, closedhand_bits, closedhandm_bits);
     case Qt::DragCopyCursor:
         return QWindowsCursor::PixmapCursor(QPixmap(copyDragCursorXpmC), QPoint(0, 0));
     case Qt::DragMoveCursor:
@@ -454,7 +456,7 @@ QWindowsCursor::PixmapCursor QWindowsCursor::customCursor(Qt::CursorShape cursor
         { Qt::DragLinkCursor, 64, "draglinkcursor_64.png", 0, 0 }
     };
 
-    const QSize cursorSize = systemCursorSize(screen);
+    const QSize cursorSize = screenCursorSize(screen);
     const QWindowsCustomPngCursor *sEnd = pngCursors + sizeof(pngCursors) / sizeof(pngCursors[0]);
     const QWindowsCustomPngCursor *bestFit = nullptr;
     int sizeDelta = INT_MAX;
@@ -507,7 +509,7 @@ HCURSOR QWindowsCursor::createCursorFromShape(Qt::CursorShape cursorShape, const
 
     switch (cursorShape) {
     case Qt::BlankCursor: {
-        QImage blank = QImage(systemCursorSize(screen), QImage::Format_Mono);
+        QImage blank = QImage(systemCursorSize(), QImage::Format_Mono);
         blank.fill(0); // ignore color table
         return createBitmapCursor(blank, blank);
     }