8149849: [hidpi] DnD issues (cannot DnD from JFileChooser to JEditorPane or other text component) when scale > 1

Reviewed-by: prr, serb

jdk/src/java.desktop/windows/native/libawt/windows/awt_DnDDT.cpp

@@ -127,6 +127,16 @@ ULONG __stdcall AwtDropTarget::Release() {
     return (ULONG)refs;
 }
 
+void ScaleDown(POINT &cp, HWND m_window) {
+    int screen = AwtWin32GraphicsDevice::DeviceIndexForWindow(m_window);
+    Devices::InstanceAccess devices;
+    AwtWin32GraphicsDevice* device = devices->GetDevice(screen);
+    if (device) {
+        cp.x = device->ScaleDownX(cp.x);
+        cp.y = device->ScaleDownY(cp.y);
+    }
+}
+
 /**
  * DragEnter
  */
@@ -176,6 +186,7 @@ HRESULT __stdcall AwtDropTarget::DragEnter(IDataObject __RPC_FAR *pDataObj, DWOR
 
         cp.x = pt.x - wr.left;
         cp.y = pt.y - wr.top;
+        ScaleDown(cp, m_window);
 
         jint actions = call_dTCenter(env, m_dtcp, m_target,
                                      (jint)cp.x, (jint)cp.y,
@@ -237,6 +248,7 @@ HRESULT __stdcall AwtDropTarget::DragOver(DWORD grfKeyState, POINTL pt, DWORD __
 
     cp.x = pt.x - wr.left;
     cp.y = pt.y - wr.top;
+    ScaleDown(cp, m_window);
 
     actions = call_dTCmotion(env, m_dtcp, m_target,(jint)cp.x, (jint)cp.y,
                              ::convertDROPEFFECTToActions(mapModsToDROPEFFECT(*pdwEffect, grfKeyState)),
@@ -336,6 +348,7 @@ HRESULT __stdcall AwtDropTarget::Drop(IDataObject __RPC_FAR *pDataObj, DWORD grf
 
     cp.x = pt.x - wr.left;
     cp.y = pt.y - wr.top;
+    ScaleDown(cp, m_window);
 
     m_dropActions = java_awt_dnd_DnDConstants_ACTION_NONE;
 

jdk/test/javax/swing/JTextArea/8149849/DNDTextToScaledArea.java

@@ -0,0 +1,125 @@
+/*
+ * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+import java.awt.BorderLayout;
+import java.awt.Component;
+import java.awt.Dimension;
+import java.awt.Point;
+import java.awt.Robot;
+import java.awt.event.InputEvent;
+import javax.swing.JFrame;
+import javax.swing.JPanel;
+import javax.swing.JTextArea;
+import javax.swing.SwingUtilities;
+
+/**
+ * @test
+ * @bug 8149849
+ * @summary [hidpi] DnD issues (cannot DnD from JFileChooser to JEditorPane or
+ *          other text component) when scale > 1
+ * @run main/othervm -Dsun.java2d.uiScale=2 DNDTextToScaledArea
+ */
+public class DNDTextToScaledArea {
+
+    private static final String TEXT = "ABCDEFGH";
+    private static JFrame frame;
+    private static JTextArea srcTextArea;
+    private static JTextArea dstTextArea;
+    private static volatile Point srcPoint;
+    private static volatile Point dstPoint;
+    private static volatile boolean passed = false;
+
+    public static void main(String[] args) throws Exception {
+        Robot robot = new Robot();
+        robot.setAutoDelay(50);
+
+        SwingUtilities.invokeAndWait(DNDTextToScaledArea::createAndShowGUI);
+        robot.waitForIdle();
+
+        SwingUtilities.invokeAndWait(() -> {
+            srcPoint = getPoint(srcTextArea, 0.1);
+            dstPoint = getPoint(dstTextArea, 0.75);
+        });
+        robot.waitForIdle();
+
+        dragAndDrop(robot, srcPoint, dstPoint);
+        robot.waitForIdle();
+
+        SwingUtilities.invokeAndWait(() -> {
+            passed = TEXT.equals(dstTextArea.getText());
+            frame.dispose();
+        });
+        robot.waitForIdle();
+
+        if (!passed) {
+            throw new RuntimeException("Text Drag and Drop failed!");
+        }
+    }
+
+    private static void createAndShowGUI() {
+
+        frame = new JFrame();
+        frame.setSize(300, 300);
+        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+
+        JPanel panel = new JPanel(new BorderLayout());
+
+        srcTextArea = new JTextArea(TEXT);
+        srcTextArea.setDragEnabled(true);
+        srcTextArea.selectAll();
+        dstTextArea = new JTextArea();
+
+        panel.add(dstTextArea, BorderLayout.CENTER);
+        panel.add(srcTextArea, BorderLayout.SOUTH);
+
+        frame.getContentPane().add(panel);
+        frame.setVisible(true);
+    }
+
+    private static Point getPoint(Component component, double scale) {
+        Point point = component.getLocationOnScreen();
+        Dimension bounds = component.getSize();
+        point.translate((int) (bounds.width * scale), (int) (bounds.height * scale));
+        return point;
+    }
+
+    public static void dragAndDrop(Robot robot, Point src, Point dst) throws Exception {
+
+        int x1 = src.x;
+        int y1 = src.y;
+        int x2 = dst.x;
+        int y2 = dst.y;
+        robot.mouseMove(x1, y1);
+        robot.mousePress(InputEvent.BUTTON1_MASK);
+
+        float dmax = (float) Math.max(Math.abs(x2 - x1), Math.abs(y2 - y1));
+        float dx = (x2 - x1) / dmax;
+        float dy = (y2 - y1) / dmax;
+
+        for (int i = 0; i <= dmax; i += 5) {
+            robot.mouseMove((int) (x1 + dx * i), (int) (y1 + dy * i));
+        }
+
+        robot.mouseRelease(InputEvent.BUTTON1_MASK);
+    }
+}