HiDPI: introduced (optional) repaint manager that fixes incomplete component paintings at 125% or 175% scaling on Windows (issues #860 and #582)

flatlaf-core/src/main/java/com/formdev/flatlaf/util/HiDPIUtils.java

@@ -26,6 +26,7 @@ import java.awt.geom.AffineTransform;
 import java.awt.geom.Rectangle2D;
 import java.text.AttributedCharacterIterator;
 import javax.swing.JComponent;
+import javax.swing.RepaintManager;
 import com.formdev.flatlaf.FlatSystemProperties;
 
 /**
@@ -377,6 +378,9 @@ public class HiDPIUtils
 		//   Also RepaintManager "merges" the two repaints into one.
 		c.repaint( x, y, width, height );
 
+		if( RepaintManager.currentManager( c ) instanceof HiDPIRepaintManager )
+			return;
+
 		// if necessary, also repaint given area in first ancestor that is larger than component
 		// to avoid clipping issue (see needsSpecialRepaint())
 		if( needsSpecialRepaint( c, x, y, width, height ) ) {
@@ -485,4 +489,79 @@ public class HiDPIUtils
 
 		return true;
 	}
+
+	/**
+	 * Installs a {@link HiDPIRepaintManager} on Windows when running in Java 9+,
+	 * but only if default repaint manager is currently installed.
+	 * <p>
+	 * Invoke once on application startup.
+	 * Compatible with all/other L&Fs.
+	 *
+	 * @since 3.5
+	 */
+	public static void installHiDPIRepaintManager() {
+		if( !SystemInfo.isJava_9_orLater || !SystemInfo.isWindows )
+			return;
+
+		RepaintManager manager = RepaintManager.currentManager( (Component) null );
+		if( manager.getClass() == RepaintManager.class )
+			RepaintManager.setCurrentManager( new HiDPIRepaintManager() );
+	}
+
+	/**
+	 * Similar to {@link #repaint(Component, int, int, int, int)},
+	 * but invokes callback instead of invoking {@link Component#repaint(int, int, int, int)}.
+	 * <p>
+	 * For use in custom repaint managers.
+	 *
+	 * @since 3.5
+	 */
+	public static void addDirtyRegion( JComponent c, int x, int y, int width, int height, DirtyRegionCallback callback ) {
+		if( needsSpecialRepaint( c, x, y, width, height ) ) {
+			int x2 = x + c.getX();
+			int y2 = y + c.getY();
+			for( Component p = c.getParent(); p != null; p = p.getParent() ) {
+				x2 += p.getX();
+				y2 += p.getY();
+				if( x2 + width < p.getWidth() && y2 + height < p.getHeight() && p instanceof JComponent ) {
+					callback.addDirtyRegion( (JComponent) p, x2, y2, width, height );
+					return;
+				}
+			}
+		}
+
+		callback.addDirtyRegion( c, x, y, width, height );
+	}
+
+	//---- interface DirtyRegionCallback --------------------------------------
+
+	/**
+	 * For {@link HiDPIUtils#addDirtyRegion(JComponent, int, int, int, int, DirtyRegionCallback)}.
+	 *
+	 * @since 3.5
+	 */
+	public interface DirtyRegionCallback {
+		void addDirtyRegion( JComponent c, int x, int y, int w, int h );
+	}
+
+	//---- class HiDPIRepaintManager ------------------------------------------
+
+	/**
+	 * A repaint manager that fixes a problem in Swing when repainting components
+	 * at some scale factors (e.g. 125%, 175%, etc) on Windows.
+	 * <p>
+	 * Use {@link HiDPIUtils#installHiDPIRepaintManager()} to install it.
+	 * <p>
+	 * See {@link HiDPIUtils#repaint(Component, int, int, int, int)} for details.
+	 *
+	 * @since 3.5
+	 */
+	public static class HiDPIRepaintManager
+		extends RepaintManager
+	{
+		@Override
+		public void addDirtyRegion( JComponent c, int x, int y, int w, int h ) {
+			HiDPIUtils.addDirtyRegion( c, x, y, w, h, super::addDirtyRegion );
+		}
+	}
 }

flatlaf-demo/src/main/java/com/formdev/flatlaf/demo/FlatLafDemo.java

@@ -96,6 +96,9 @@ public class FlatLafDemo
 			// use Roboto Mono font
 //			FlatLaf.setPreferredMonospacedFontFamily( FlatRobotoMonoFont.FAMILY );
 
+			// install own repaint manager to fix repaint issues at 125%, 175%, 225%, ... on Windows
+//			HiDPIUtils.installHiDPIRepaintManager();
+
 			// application specific UI defaults
 			FlatLaf.registerCustomDefaultsSource( "com.formdev.flatlaf.demo" );
 

flatlaf-testing/src/main/java/com/formdev/flatlaf/testing/FlatHiDPITest.java

@@ -70,6 +70,8 @@ public class FlatHiDPITest
 				return;
 			}
 
+//			HiDPIUtils.installHiDPIRepaintManager();
+
 			FlatLaf.setGlobalExtraDefaults( Collections.singletonMap( "@accentColor", "#f00" ) );
 			FlatLightLaf.setup();
 
@@ -124,6 +126,8 @@ public class FlatHiDPITest
 		y += 20;
 		addAtProblematicXY( 0, y, 16, 40, 20, "JScrollBar", () -> new JScrollBar( JScrollBar.VERTICAL ) );
 		y += 60;
+		addAtProblematicXY( 0, y, 82, 60, 88, "JScrollPane", () -> new JScrollPane( new JTree() ) );
+		y += 80;
 		addAtProblematicXY( 0, y, 80, 16, 88, "JProgressBar", () -> {
 			JProgressBar c = new JProgressBar();
 			c.setValue( 60 );
@@ -138,7 +142,7 @@ public class FlatHiDPITest
 		} );
 
 		frame.getContentPane().add( testPanel );
-		frame.setSize( 400, 300 );
+		frame.setSize( 400, 400 );
 		frame.setVisible( true );
 	}