Bug 741 HiDPI: Add ScalableSurface.getNativeSurfaceScale(..) to compute surface DPI ; Add NEWT Window.getPixelsPerMM(..) to query surface DPI

With HiDPI and surface scale, we need knowledge of the native surface's pixel-scale
matching the monitor's pixel-per-millimeter value.

Preserving the queried native pixel-scale and exposing it via
ScalableSurface.getNativeSurfaceScale(..) to compute surface DPI.

Add NEWT Window.getPixelsPerMM(..) to query surface DPI.

Surface DPI is demonstrated in GraphUI's GPUUISceneGLListener0A .. and TestRulerNEWT01, etc ..

3 files changed, 45 insertions, 8 deletions

diff --git a/src/newt/classes/com/jogamp/newt/MonitorDevice.java b/src/newt/classes/com/jogamp/newt/MonitorDevice.java
index 8e5d305dd..a65675204 100644
--- a/src/newt/classes/com/jogamp/newt/MonitorDevice.java
+++ b/src/newt/classes/com/jogamp/newt/MonitorDevice.java
@@ -34,6 +34,7 @@ import javax.media.nativewindow.util.DimensionImmutable;
 import javax.media.nativewindow.util.Rectangle;
 import javax.media.nativewindow.util.RectangleImmutable;
 import javax.media.nativewindow.util.SurfaceSize;
+
 import com.jogamp.common.util.ArrayHashSet;
 
 /**
@@ -124,29 +125,34 @@ public abstract class MonitorDevice {
     }
 
     /**
-     * Stores the <i>pixels per millimeter</i> value according to <i>current</i> {@link MonitorMode}
-     * {@link SurfaceSize#getResolution() SurfaceSize's resolution} in the given storage <code>ppmmStore</code>.
+     * Returns the <i>pixels per millimeter</i> value according to the <i>current</i> {@link MonitorMode mode}'s
+     * {@link SurfaceSize#getResolution() surface resolution}.
      * <p>
      * To convert the result to <i>dpi</i>, i.e. dots-per-inch, multiply both components with <code>25.4f</code>.
      * </p>
+     * @param ppmmStore float[2] storage for the ppmm result
+     * @return the passed storage containing the ppmm for chaining
      */
-    public final void getPixelsPerMM(final float[] ppmmStore) {
-        final MonitorMode mode = getCurrentMode();
-        getPixelsPerMM(mode, ppmmStore);
+    public final float[] getPixelsPerMM(final float[] ppmmStore) {
+        return getPixelsPerMM(getCurrentMode(), ppmmStore);
     }
 
     /**
-     * Stores the <i>pixels per millimeter</i> value according to the given {@link MonitorMode}
-     * {@link SurfaceSize#getResolution() SurfaceSize's resolution} in the given storage <code>ppmmStore</code>.
+     * Returns the <i>pixels per millimeter</i> value according to the given {@link MonitorMode mode}'s
+     * {@link SurfaceSize#getResolution() surface resolution}.
      * <p>
      * To convert the result to <i>dpi</i>, i.e. dots-per-inch, multiply both components with <code>25.4f</code>.
      * </p>
+     * @param mode
+     * @param ppmmStore float[2] storage for the ppmm result
+     * @return the passed storage containing the ppmm for chaining
      */
-    public final void getPixelsPerMM(final MonitorMode mode, final float[] ppmmStore) {
+    public final float[] getPixelsPerMM(final MonitorMode mode, final float[] ppmmStore) {
         final DimensionImmutable sdim = getSizeMM();
         final DimensionImmutable spix = mode.getSurfaceSize().getResolution();
         ppmmStore[0] = (float)spix.getWidth() / (float)sdim.getWidth();
         ppmmStore[1] = (float)spix.getHeight() / (float)sdim.getHeight();
+        return ppmmStore;
     }
 
     /**
diff --git a/src/newt/classes/com/jogamp/newt/Window.java b/src/newt/classes/com/jogamp/newt/Window.java
index 08236ae67..600ecee52 100644
--- a/src/newt/classes/com/jogamp/newt/Window.java
+++ b/src/newt/classes/com/jogamp/newt/Window.java
@@ -49,6 +49,7 @@ import javax.media.nativewindow.ScalableSurface;
 import javax.media.nativewindow.WindowClosingProtocol;
 import javax.media.nativewindow.util.Rectangle;
 import javax.media.nativewindow.util.RectangleImmutable;
+import javax.media.nativewindow.util.SurfaceSize;
 
 /**
  * Specifying NEWT's Window functionality:
@@ -254,6 +255,26 @@ public interface Window extends NativeWindow, WindowClosingProtocol, ScalableSur
     Rectangle getBounds();
 
     /**
+     * Returns the <i>pixels per millimeter</i> of this window's {@link NativeSurface}
+     * according to the {@link #getMainMonitor() main monitor}'s <i>current</i> {@link MonitorMode mode}'s
+     * {@link SurfaceSize#getResolution() surface resolution}.
+     * <p>
+     * Method takes the {@link #getCurrentSurfaceScale(int[]) current surface-scale} and {@link #getNativeSurfaceScale(int[]) native surface-scale}
+     * into account, i.e.:
+     * <pre>
+     *    surfacePpMM = monitorPpMM * currentSurfaceScale / nativeSurfaceScale,
+     *    with PpMM == pixel per millimeter
+     * </pre>
+     * </p>
+     * <p>
+     * To convert the result to <i>dpi</i>, i.e. dots-per-inch, multiply both components with <code>25.4f</code>.
+     * </p>
+     * @param ppmmStore float[2] storage for the ppmm result
+     * @return the passed storage containing the ppmm for chaining
+     */
+    float[] getPixelsPerMM(final float[] ppmmStore);
+
+    /**
      * Sets the size of the window's client area in window units, excluding decorations.
      *
      * <p>
diff --git a/src/newt/classes/com/jogamp/newt/opengl/GLWindow.java b/src/newt/classes/com/jogamp/newt/opengl/GLWindow.java
index 2991bb98a..cdc4f1217 100644
--- a/src/newt/classes/com/jogamp/newt/opengl/GLWindow.java
+++ b/src/newt/classes/com/jogamp/newt/opengl/GLWindow.java
@@ -404,6 +404,16 @@ public class GLWindow extends GLAutoDrawableBase implements GLAutoDrawable, Wind
     }
 
     @Override
+    public final int[] getNativeSurfaceScale(final int[] result) {
+        return window.getNativeSurfaceScale(result);
+    }
+
+    @Override
+    public final float[] getPixelsPerMM(final float[] ppmmStore) {
+        return window.getPixelsPerMM(ppmmStore);
+    }
+
+    @Override
     public final void setPosition(int x, int y) {
         window.setPosition(x, y);
     }