Add devicePixelRatio support to the Windows QPA plugin.

This adds support for the environment variable
QT_DEVICE_PIXEL_RATIO for the Windows platform plugin.

Task-number: QTBUG-38993
Task-number: QTBUG-38858
Change-Id: I6831eb6d3a09a80be7bbef46395e91531b61cc50
Reviewed-by: Alessandro Portale <alessandro.portale@digia.com>
Reviewed-by: Paul Olav Tvete <paul.tvete@digia.com>

1 files changed, 19 insertions, 8 deletions

diff --git a/src/plugins/platforms/windows/qwindowsdrag.cpp b/src/plugins/platforms/windows/qwindowsdrag.cpp
index 716d892472..e1b4aca0c4 100644
--- a/src/plugins/platforms/windows/qwindowsdrag.cpp
+++ b/src/plugins/platforms/windows/qwindowsdrag.cpp
@@ -41,6 +41,7 @@
 
 #include "qwindowsdrag.h"
 #include "qwindowscontext.h"
+#include "qwindowsscaling.h"
 #ifndef QT_NO_CLIPBOARD
 #  include "qwindowsclipboard.h"
 #endif
@@ -50,6 +51,7 @@
 #include "qwindowswindow.h"
 #include "qwindowsmousehandler.h"
 #include "qwindowscursor.h"
+#include "qwindowsscaling.h"
 
 #include <QtGui/QMouseEvent>
 #include <QtGui/QPixmap>
@@ -295,12 +297,19 @@ void QWindowsOleDropSource::createCursors()
     const QDrag *drag = m_drag->currentDrag();
     const QPixmap pixmap = drag->pixmap();
     const bool hasPixmap = !pixmap.isNull();
+    const int scaleFactor = QWindowsScaling::factor();
+    const QSize pixmapSizeDp = pixmap.size() * scaleFactor;
+    const bool scalePixmap = hasPixmap
+        && m_mode != TouchDrag // Touch drag: pixmap is shown in a separate QWindow, which will be scaled.
+        && (scaleFactor != 1 && scaleFactor != qRound(pixmap.devicePixelRatio()));
+    const QPixmap drawPixmap = scalePixmap
+        ? pixmap.scaled(pixmapSizeDp, Qt::KeepAspectRatio, Qt::SmoothTransformation) : pixmap;
 
     Qt::DropAction actions[] = { Qt::MoveAction, Qt::CopyAction, Qt::LinkAction, Qt::IgnoreAction };
     int actionCount = int(sizeof(actions) / sizeof(actions[0]));
     if (!hasPixmap)
         --actionCount; // No Qt::IgnoreAction unless pixmap
-    const QPoint hotSpot = drag->hotSpot();
+    const QPoint hotSpot = drag->hotSpot() * scaleFactor;
     for (int cnum = 0; cnum < actionCount; ++cnum) {
         const Qt::DropAction action = actions[cnum];
         QPixmap cursorPixmap = drag->dragCursor(action);
@@ -320,15 +329,14 @@ void QWindowsOleDropSource::createCursors()
 
         if (hasPixmap) {
             const int x1 = qMin(-hotSpot.x(), 0);
-            const int x2 = qMax(pixmap.width() - hotSpot.x(), cursorPixmap.width());
+            const int x2 = qMax(pixmapSizeDp.width() - hotSpot.x(), cursorPixmap.width());
             const int y1 = qMin(-hotSpot.y(), 0);
-            const int y2 = qMax(pixmap.height() - hotSpot.y(), cursorPixmap.height());
+            const int y2 = qMax(pixmapSizeDp.height() - hotSpot.y(), cursorPixmap.height());
             QPixmap newCursor(x2 - x1 + 1, y2 - y1 + 1);
             newCursor.fill(Qt::transparent);
             QPainter p(&newCursor);
-            const QRect srcRect = pixmap.rect();
             const QPoint pmDest = QPoint(qMax(0, -hotSpot.x()), qMax(0, -hotSpot.y()));
-            p.drawPixmap(pmDest, pixmap, srcRect);
+            p.drawPixmap(pmDest, drawPixmap);
             p.drawPixmap(qMax(0, hotSpot.x()),qMax(0, hotSpot.y()), cursorPixmap);
             newPixmap = newCursor;
             newHotSpot = QPoint(qMax(0, hotSpot.x()), qMax(0, hotSpot.y()));
@@ -454,7 +462,7 @@ QWindowsOleDropSource::GiveFeedback(DWORD dwEffect)
             if (!m_touchDragWindow)
                 m_touchDragWindow = new QWindowsDragCursorWindow;
             m_touchDragWindow->setPixmap(e.pixmap);
-            m_touchDragWindow->setFramePosition(QWindowsCursor::mousePosition() - e.hotSpot);
+            m_touchDragWindow->setFramePosition((QWindowsCursor::mousePosition() - e.hotSpot) / QWindowsScaling::factor());
             if (!m_touchDragWindow->isVisible())
                 m_touchDragWindow->show();
             break;
@@ -530,7 +538,9 @@ void QWindowsOleDropTarget::handleDrag(QWindow *window, DWORD grfKeyState,
     QGuiApplicationPrivate::mouse_buttons = QWindowsMouseHandler::keyStateToMouseButtons(grfKeyState);
 
     const QPlatformDragQtResponse response =
-          QWindowSystemInterface::handleDrag(window, windowsDrag->dropData(), m_lastPoint, actions);
+          QWindowSystemInterface::handleDrag(window, windowsDrag->dropData(),
+                                             m_lastPoint / QWindowsScaling::factor(),
+                                             actions);
 
     m_answerRect = response.answerRect();
     const Qt::DropAction action = response.acceptedAction();
@@ -622,7 +632,8 @@ QWindowsOleDropTarget::Drop(LPDATAOBJECT pDataObj, DWORD grfKeyState,
     QWindowsDrag *windowsDrag = QWindowsDrag::instance();
 
     const QPlatformDropQtResponse response =
-        QWindowSystemInterface::handleDrop(m_window, windowsDrag->dropData(), m_lastPoint,
+        QWindowSystemInterface::handleDrop(m_window, windowsDrag->dropData(),
+                                           m_lastPoint / QWindowsScaling::factor(),
                                            translateToQDragDropActions(*pdwEffect));
 
     if (response.isAccepted()) {