Fixes for drag and drop when DPI scaling in use, reported by NASAWorldWind#274 (comment)

Author: gbburkhardt

src/gov/nasa/worldwind/drag/DragContext.java

@@ -41,16 +41,16 @@
 public class DragContext
 {
     /**
-     * In accordance with the AWT screen coordinates the top left point of the window is the origin.
+     * In accordance with the GL surface coordinates the top left point of the window is the origin.
      */
     protected Point point;
     /**
-     * In accordance with the AWT screen coordinates the top left point of the window is the origin. This point is the
+     * In accordance with the GL surface coordinates the top left point of the window is the origin. This point is the
      * previous screen point.
      */
     protected Point previousPoint;
     /**
-     * In accordance with the AWT screen coordinates the top left point of the window is the origin. This point refers
+     * In accordance with the GL surface coordinates the top left point of the window is the origin. This point refers
      * to the initial point of the drag event.
      */
     protected Point initialPoint;
@@ -81,19 +81,19 @@ public DragContext()
     }
 
     /**
-     * Returns the current screen point with the origin at the top left corner of the window.
+     * Returns the current GL surface point with the origin at the top left corner of the window.
      *
-     * @return the current screen point.
+     * @return the current GL surface point.
      */
     public Point getPoint()
     {
         return point;
     }
 
     /**
-     * Set the {@link DragContext} current screen point.
+     * Set the {@link DragContext} current GL surface point.
      *
-     * @param point the point to assign to the current screen point.
+     * @param point the point to assign to the current GL surface point.
      *
      * @throws IllegalArgumentException if the point is null.
      */
@@ -110,7 +110,7 @@ public void setPoint(Point point)
     }
 
     /**
-     * Returns the previous screen point with the origin at the top left corner of the window.
+     * Returns the previous GL surface point with the origin at the top left corner of the window.
      *
      * @return the previous point.
      */
@@ -120,9 +120,9 @@ public Point getPreviousPoint()
     }
 
     /**
-     * Set the {@link DragContext} previous screen point.
+     * Set the {@link DragContext} previous GL surface point.
      *
-     * @param previousPoint the screen point to assign to the previous screen point.
+     * @param previousPoint the GL surface point to assign to the previous screen point.
      *
      * @throws IllegalArgumentException if the previousPoint is null.
      */
@@ -139,20 +139,20 @@ public void setPreviousPoint(Point previousPoint)
     }
 
     /**
-     * Returns the initial screen point with the origin at the top left corner of the window. The initial point is the
-     * screen point at the initiation of the drag event.
+     * Returns the initial GL surface point with the origin at the top left corner of the window. The initial point is the
+     * GL surface point at the initiation of the drag event.
      *
-     * @return the initial screen point.
+     * @return the initial GL surface point.
      */
     public Point getInitialPoint()
     {
         return initialPoint;
     }
 
     /**
-     * Set the {@link DragContext} initial screen point.
+     * Set the {@link DragContext} initial GL surface point.
      *
-     * @param initialPoint the screen point to assign to the initial screen point.
+     * @param initialPoint the GL surface point to assign to the initial screen point.
      *
      * @throws IllegalArgumentException if the initialPoint is null.
      */

src/gov/nasa/worldwind/drag/DraggableSupport.java

@@ -428,9 +428,7 @@ protected Vec4 computeScreenOffsetFromReferencePosition(Position dragObjectRefer
 
         Vec4 screenPointOffset = new Vec4(
             dragContext.getInitialPoint().getX() - dragObjectScreenPoint.getX(),
-            dragContext.getInitialPoint().getY() - (
-                dragContext.getView().getViewport().getHeight()
-                    - dragObjectScreenPoint.getY() - 1.0)
+            dragContext.getInitialPoint().getY() - dragObjectScreenPoint.getY()
         );
 
         return screenPointOffset;

src/gov/nasa/worldwind/render/DrawContext.java

@@ -1051,4 +1051,11 @@ public interface DrawContext extends WWObject, Disposable
      * Convert AWT effective screen location to GL surface location using DPI scaling.
      */
     int [] awtPointToGLpoint(Point pt);
+    
+    /**
+     * Convert GL surface coordinate point to AWT device point using DPI scaling.
+     * @param glPoint
+     * @return
+     */
+    public Point glPointToAwtPoint(Point glPoint);
 }

src/gov/nasa/worldwind/render/DrawContextImpl.java

@@ -1752,7 +1752,17 @@ else if (altitudeMode == WorldWind.RELATIVE_TO_GROUND)
 		// Convert to GL surface coordinates
 		int [] glSurfacePt = drawable.getNativeSurface().convertToPixelUnits(awtPt);
 		int glSurfaceHeight = drawable.getSurfaceHeight();
-		glSurfacePt[1] = glSurfaceHeight - glSurfacePt[1] - 1;
+		glSurfacePt[1] = glSurfaceHeight-1 - glSurfacePt[1];
 		return glSurfacePt;
 	}
+	    
+    public Point glPointToAwtPoint(Point glPoint) {
+		GLDrawable drawable = glContext.getGLDrawable();
+		if (drawable == null) return glPoint;
+
+		final int viewportHeight = getView().getViewport().height;
+		int [] glPt = { glPoint.x, viewportHeight-1 - glPoint.y };
+        getGLDrawable().getNativeSurface().convertToWindowUnits(glPt);
+        return new Point(glPt[0], glPt[1]);    	
+    }
 }

src/gov/nasa/worldwind/render/ScreenImage.java

@@ -78,13 +78,6 @@ public class ScreenImage extends WWObjectImpl implements Renderable, Exportable
      * is computed in <code>computeOffsets</code> and used in <code>draw</code> Initially <code>null</code>.
      */
     protected Point screenLocation;
-    /**
-     * Indicates the location of this screen image in the viewport (on the screen) in AWT coordinates. This property is
-     * assigned in <code>setScreenLocation</code> and <code>computeOffsets</code>. In <code>computeOffsets</code>, this
-     * is computed by converting the <code>screenLocation</code> from OpenGL coordinates to AWT coordinates. Initially
-     * <code>null</code>.
-     */
-    protected Point awtScreenLocation;
     protected double dx;
     protected double dy;
     protected Layer pickLayer;
@@ -122,7 +115,7 @@ public void render(DrawContext dc)
      */
     public Point getScreenLocation()
     {
-        return this.awtScreenLocation;
+        return this.screenLocation;
     }
 
     /**
@@ -136,7 +129,7 @@ public Point getScreenLocation()
     public Point getScreenLocation(DrawContext dc)
     {
         this.computeOffsets(dc);
-        return this.awtScreenLocation;
+        return this.screenLocation;
     }
 
     /**
@@ -151,17 +144,16 @@ public Point getScreenLocation(DrawContext dc)
      */
     public void setScreenLocation(Point screenLocation)
     {
-        // Use units PIXELS for the X screen offset, and and INSET_PIXELS for the Y screen offset. The Offset is in
-        // OpenGL coordinates with the origin in the lower-left corner, but the Point is in AWT coordinates with the
-        // origin in the upper-left corner. This offset translates the origin from the lower-left to the upper-left
-        // corner.
-        this.screenOffset = new Offset(screenLocation.getX(), screenLocation.getY(), AVKey.PIXELS, AVKey.INSET_PIXELS);
+        // Use units PIXELS for the X screen offset, and and PIXELS for the Y screen offset. The Offset is in
+        // OpenGL coordinates with the origin in the lower-left corner, as is the Point.  This offset 
+    	// translates the origin from the lower-left to the upper-left corner.
+        this.screenOffset = new Offset(screenLocation.getX(), screenLocation.getY(), AVKey.PIXELS, AVKey.PIXELS);
         this.imageOffset = new Offset(0.5, 0.5, AVKey.FRACTION, AVKey.FRACTION);
 
         // Set cached screen location to the initial screen location so that it can be retrieved if getScreenLocation()
         // is called before the image is rendered. This maintains backward compatibility with the previous behavior of
         // ScreenImage.
-        this.awtScreenLocation = new Point(screenLocation);
+        this.screenLocation = new Point(screenLocation);
     }
 
     /**
@@ -544,12 +536,7 @@ else if (this.getImageSource() == null) // If no image source is set, draw a rec
             {
                 this.screenLocation = new Point(viewportWidth / 2, viewportHeight / 2);
             }
-
-            // Convert the screen location from OpenGL to AWT coordinates and store the result in awtScreenLocation. The
-            // awtScreenLocation property is used in getScreenLocation to indicate the screen location in AWT
-            // coordinates.
-            this.awtScreenLocation = new Point(this.screenLocation.x, viewportHeight - this.screenLocation.y);
-
+          
             Point.Double overlayPoint;
             if (this.imageOffset != null)
                 overlayPoint = this.imageOffset.computeOffset(this.width, this.height, null, null);