JNA Windows Scaling (#45)

JNA Windows Scaling

app/src/processing/app/Platform.java

@@ -411,9 +411,9 @@ public class Platform {
 
 
   // . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
-
-
-  static public int getSystemDPI() {
-    return inst.getSystemDPI();
+  
+  static public float getSystemZoom() {
+    return inst.getSystemZoom();
   }
+
 }

app/src/processing/app/platform/DefaultPlatform.java

@@ -54,6 +54,8 @@ import processing.app.Preferences;
 public class DefaultPlatform {
   Base base;
 
+  private final float ZOOM_DEFAULT_SIZING = 1;
+  private final int DEFAULT_DPI = 96;
 
   public void initBase(Base base) {
     this.base = base;
@@ -157,8 +159,34 @@ public class DefaultPlatform {
 
   // . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
 
-
-  public int getSystemDPI() {
-    return 96;
+  /**
+   * Get the zoom or display scaling requested by the operating system.
+   *
+   * <p>
+   * Get the operating system zoom setting that Processing may use to resize
+   * internal elements depending on user preferences. Note that some operating
+   * systems will perform zooming in a way that is transparent to the
+   * the applications. If that is the case, this will return 1. Otherwise,
+   * the operating system will not automatically resize UI elements and this
+   * will return a value other than 1, meaning that Processing may need to
+   * resize elements on its own depending on user preferences.
+   * </p>
+   *
+   * <p>
+   * Note that this may be distinct from the system DPI and some operating
+   * systems may report a DPI of 96 while also requesting a display zooming of
+   * 125%. However, others may not report a "display scaling" but provide a
+   * DPI of 120 when the elements should have a 125% zoom. This will use the
+   * preferred method of determining the appropriate zoom given the platform
+   * in use. Using this system display scaling percentage approach instead of
+   * returning DPI directly is preferred after JEP 263.
+   * </p>
+   *
+   * @return The zoom level where 1.0 means 100% (no zoom) and 1.25 means 
+   *    125% (25% additional zoom).
+   */
+  public float getSystemZoom() {
+    return ZOOM_DEFAULT_SIZING;
   }
+
 }

app/src/processing/app/platform/WindowsPlatform.java

@@ -22,14 +22,15 @@
 
 package processing.app.platform;
 
+import java.awt.*;
 import java.io.File;
 import java.io.IOException;
 import java.io.UnsupportedEncodingException;
+import java.util.Optional;
 
 import com.sun.jna.Library;
 import com.sun.jna.Native;
-import com.sun.jna.platform.win32.Shell32Util;
-import com.sun.jna.platform.win32.ShlObj;
+import com.sun.jna.platform.win32.*;
 
 import processing.app.Base;
 import processing.app.Messages;
@@ -61,10 +62,16 @@ public class WindowsPlatform extends DefaultPlatform {
     "\\" + APP_NAME.toLowerCase() + ".exe \"%1\"";
   static final String REG_DOC = APP_NAME + ".Document";
 
-  // Starting with Java 9, the scaling is done automatically. If DPI is
-  // used to scaling within the application, one ends up with 2x the
-  // expected scale. See JEP 263.
-  private static final int WINDOWS_NATIVE_DPI = 96;
+  private static final float RESOLUTION_AT_NO_SCALE = 96;
+  private static final int VERTRES = 10;
+  private static final int DESKTOPVERTRES = 117;
+
+  private Optional<Float> cachedDisplayScaling;
+
+  public WindowsPlatform() {
+    super();
+    cachedDisplayScaling = Optional.empty();
+  }
 
   public void initBase(Base base) {
     super.initBase(base);
@@ -629,10 +636,28 @@ public class WindowsPlatform extends DefaultPlatform {
 
   // . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
 
+  public float getSystemZoom() {
+    if (cachedDisplayScaling.isEmpty()) {
+      cachedDisplayScaling = Optional.of(calculateSystemZoom());
+    }
 
-  public int getSystemDPI() {
-    // Note that this is supported "natively" within Java - See JEP 263.
-    return WINDOWS_NATIVE_DPI;
+    return cachedDisplayScaling.get();
+  }
+
+  private float calculateSystemZoom() {
+    WinDef.HDC hdc = GDI32.INSTANCE.CreateCompatibleDC(null);
+
+    if (hdc == null) {
+      float resolution = Toolkit.getDefaultToolkit().getScreenResolution();
+      return resolution / RESOLUTION_AT_NO_SCALE;
+    }
+
+    float virtualResolution = GDI32.INSTANCE.GetDeviceCaps(hdc, VERTRES);
+    float logicalResolution = GDI32.INSTANCE.GetDeviceCaps(hdc, DESKTOPVERTRES);
+
+    GDI32.INSTANCE.DeleteDC(hdc);
+
+    return logicalResolution / virtualResolution;
   }
 
 }

app/src/processing/app/ui/Toolkit.java

@@ -851,7 +851,7 @@ public class Toolkit {
 
   static private float parseZoom() {
     if (Preferences.getBoolean("editor.zoom.auto")) {
-      float newZoom = Platform.getSystemDPI() / 96f;
+      float newZoom = Platform.getSystemZoom();
       String percentSel = ((int) (newZoom*100)) + "%";
       Preferences.set("editor.zoom", percentSel);
       return newZoom;