Windows: Adapt custom cursors to observe the system metrics.

Change the cursors Qt provides to use freely scalable pixmap cursors
and scale them to observe system metrics. Make it possible to
use pre-saled bitmap data later by passing the system cursor size
and the intended target size into the creation function
createBitmapCursorFromData().

Task-number: QTBUG-37862
Change-Id: I23899a77f86d0b08b858a81870a57b2e6570ebbe
Reviewed-by: Alessandro Portale <alessandro.portale@digia.com>

1 files changed, 31 insertions, 10 deletions

diff --git a/src/plugins/platforms/windows/qwindowscursor.cpp b/src/plugins/platforms/windows/qwindowscursor.cpp
index e453be32ed..bfe22dac3f 100644
--- a/src/plugins/platforms/windows/qwindowscursor.cpp
+++ b/src/plugins/platforms/windows/qwindowscursor.cpp
@@ -205,12 +205,33 @@ static HCURSOR createBitmapCursor(const QImage &bbits, const QImage &mbits,
 #endif
 }
 
-static HCURSOR createBitmapCursorFromData(int size, const uchar *bits, const uchar *maskBits)
+static inline QSize systemCursorSize() { return QSize(GetSystemMetrics(SM_CXCURSOR), GetSystemMetrics(SM_CYCURSOR)); }
+static inline QSize standardCursorSize() { return QSize(32, 32); }
+
+// Create pixmap cursors from data and scale the image if the cursor size is
+// higher than the standard 32. Note that bitmap cursors as produced by
+// 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 HCURSOR createPixmapCursorFromData(const QSize &systemCursorSize,
+                                          // The cursor size the bitmap is targeted for
+                                          const QSize &bitmapTargetCursorSize,
+                                          // The actual size of the bitmap data
+                                          int bitmapSize, const uchar *bits,
+                                          const uchar *maskBits)
 {
-    const QImage rawImage = QBitmap::fromData(QSize(size, size), bits).toImage();
-    const QImage rawMaskImage = QBitmap::fromData(QSize(size, size), maskBits).toImage();
-    return createBitmapCursor(rawImage.convertToFormat(QImage::Format_Mono),
-                              rawMaskImage.convertToFormat(QImage::Format_Mono));
+    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());
+    // 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) {
+        const QTransform transform = QTransform::fromScale(factor, factor);
+        rawImage = rawImage.transformed(transform, Qt::SmoothTransformation);
+    }
+    const QPoint hotSpot(rawImage.width() / 2, rawImage.height() / 2);
+    return QWindowsCursor::createPixmapCursor(rawImage, hotSpot);
 }
 
 struct QWindowsStandardCursorMapping {
@@ -316,18 +337,18 @@ HCURSOR QWindowsCursor::createSystemCursor(const QCursor &c)
         return createBitmapCursor(bbits, mbits, c.hotSpot(), invb, invm);
     }
     case Qt::BlankCursor: {
-        QImage blank = QImage(32, 32, QImage::Format_Mono);
+        QImage blank = QImage(systemCursorSize(), QImage::Format_Mono);
         blank.fill(0); // ignore color table
         return createBitmapCursor(blank, blank);
     }
     case Qt::SplitVCursor:
-        return createBitmapCursorFromData(32, vsplit_bits, vsplitm_bits);
+        return createPixmapCursorFromData(systemCursorSize(), standardCursorSize(), 32, vsplit_bits, vsplitm_bits);
     case Qt::SplitHCursor:
-        return createBitmapCursorFromData(32, hsplit_bits, hsplitm_bits);
+        return createPixmapCursorFromData(systemCursorSize(), standardCursorSize(), 32, hsplit_bits, hsplitm_bits);
     case Qt::OpenHandCursor:
-        return createBitmapCursorFromData(16, openhand_bits, openhandm_bits);
+        return createPixmapCursorFromData(systemCursorSize(), standardCursorSize(), 16, openhand_bits, openhandm_bits);
     case Qt::ClosedHandCursor:
-        return createBitmapCursorFromData(16, closedhand_bits, closedhandm_bits);
+        return createPixmapCursorFromData(systemCursorSize(), standardCursorSize(), 16, closedhand_bits, closedhandm_bits);
     case Qt::DragCopyCursor:
     case Qt::DragMoveCursor:
     case Qt::DragLinkCursor: