Bug 1422: Emulate DPI Scaling on non-native DPI autoscale platforms (!MacOS)

Bug 1422 shows that it seems to be desired to emulate DPI scaling where
the native toolkit does not implmement the same.

On GTK, DPIUtil.mapDPIToZoom (int dpi) reads:
  double zoom = (double) dpi * 100 / 96;
  int roundedZoom = (int) Math.round (zoom);
  return roundedZoom;

While having dpi calculated as:

  dpi = 96 * GDK.gdk_monitor_get_scale_factor(monitor);

Well, this seems to exist to allow 96 dpi fixed layout to
'look' OK on high-dpi screens.
However, you get in trouble if you layout high-dpi aware,
i.e. using percentages etc.

There is one exception: If DPIUtil.useCairoAutoScale() is true, scalingFactor is 1f
and hence the scaling emulation dropped.

'DPIUtil.setUseCairoAutoScale((sx[0]*100) == scaleFactor || OS.isGNOME);'

1 files changed, 26 insertions, 3 deletions

diff --git a/src/newt/classes/com/jogamp/newt/swt/NewtCanvasSWT.java b/src/newt/classes/com/jogamp/newt/swt/NewtCanvasSWT.java
index 2930a4fd3..2615ebbb5 100644
--- a/src/newt/classes/com/jogamp/newt/swt/NewtCanvasSWT.java
+++ b/src/newt/classes/com/jogamp/newt/swt/NewtCanvasSWT.java
@@ -176,6 +176,29 @@ public class NewtCanvasSWT extends Canvas implements NativeWindowHolder, WindowC
         addListener (SWT.FocusOut, swtListener);
     }
 
+    /**
+     * Set's the NEWT {@link Window}'s size using {@link Window#setSize(int, int)}.
+     * <p>
+     * For all non-native DPI autoscale platforms, it utilizes {@link SWTAccessor#autoScaleUp(Point)}
+     * by multiplying the given {@link Rectangle} size to emulate DPI scaling, see Bug 1422.
+     * </p>
+     * <p>
+     * Currently native DPI autoscale platforms are
+     * <ul>
+     *  <li>{@link SWTAccessor#isOSX}</li>
+     * </ul>
+     * hence the emulated DPI scaling is enabled for all other platforms.
+     * </p>
+     * @param r containing desired size
+     */
+    private final void setNewtChildSize(final Rectangle r) {
+        if( !SWTAccessor.isOSX ) {
+            final Point p = SWTAccessor.autoScaleUp(new Point(r.width, r.height));
+            newtChild.setSize(p.getX(), p.getY());
+        } else {
+            newtChild.setSize(r.width, r.height);
+        }
+    }
     private final Listener swtListener = new Listener () {
         @Override
         public void handleEvent (final Event event) {
@@ -187,7 +210,7 @@ public class NewtCanvasSWT extends Canvas implements NativeWindowHolder, WindowC
                 }
                 if( validateNative() && newtChildReady ) {
                     if( postSetSize ) {
-                        newtChild.setSize(clientAreaWindow.width, clientAreaWindow.height);
+                        setNewtChildSize(clientAreaWindow);
                         postSetSize = false;
                     }
                     if( postSetPos ) {
@@ -357,7 +380,7 @@ public class NewtCanvasSWT extends Canvas implements NativeWindowHolder, WindowC
         }
         if( sizeChanged ) {
             if( newtChildReady ) {
-                newtChild.setSize(nClientAreaWindow.width, nClientAreaWindow.height);
+                setNewtChildSize(nClientAreaWindow);
                 newtChild.setSurfaceScale(pixelScale);
             } else {
                 postSetSize = true;
@@ -529,7 +552,7 @@ public class NewtCanvasSWT extends Canvas implements NativeWindowHolder, WindowC
                 newtDisplay.setEDTUtil( edtUtil );
             }
 
-            newtChild.setSize(clientAreaWindow.width, clientAreaWindow.height);
+            setNewtChildSize(clientAreaWindow);
             newtChild.reparentWindow(nativeWindow, -1, -1, Window.REPARENT_HINT_BECOMES_VISIBLE);
             newtChild.setPosition(clientAreaWindow.x, clientAreaWindow.y);
             newtChild.setVisible(true);