Linux: use X11 window manager events to resize window, if FlatLaf window decorations are enabled (issue #866)

also made drag border slightly wider (from 5 to 6 pixels) and changed drag corner width from 16 to 32 to match native windows

CHANGELOG.md

@@ -24,6 +24,9 @@ FlatLaf Change Log
 - Extras: `FlatSVGIcon` color filters now can access painting component to
   implement component state based color mappings. (issue #906)
 - Linux: Added `libflatlaf-linux-arm64.so` for Linux on ARM64. (issue #899)
+- Linux: Use X11 window manager events to resize window, if FlatLaf window
+  decorations are enabled. This gives FlatLaf windows a more "native" feeling.
+  (issue #866)
 - IntelliJ Themes:
   - Updated to latest versions and fixed various issues.
   - Support customizing through properties files. (issue #824)

flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatNativeLinuxLibrary.java

@@ -49,8 +49,17 @@ class FlatNativeLinuxLibrary
 	}
 
 	// direction for _NET_WM_MOVERESIZE message
-	// see https://specifications.freedesktop.org/wm-spec/wm-spec-latest.html
+	// see https://specifications.freedesktop.org/wm-spec/latest/ar01s04.html
-	static final int MOVE = 8;
+	static final int
+		SIZE_TOPLEFT     = 0,
+		SIZE_TOP         = 1,
+		SIZE_TOPRIGHT    = 2,
+		SIZE_RIGHT       = 3,
+		SIZE_BOTTOMRIGHT = 4,
+		SIZE_BOTTOM      = 5,
+		SIZE_BOTTOMLEFT  = 6,
+		SIZE_LEFT        = 7,
+		MOVE             = 8;
 
 	private static Boolean isXWindowSystem;
 

flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatWindowResizer.java

@@ -188,7 +188,7 @@ public abstract class FlatWindowResizer
 	protected abstract Dimension getWindowMinimumSize();
 	protected abstract Dimension getWindowMaximumSize();
 
-	protected void beginResizing( int resizeDir ) {}
+	protected void beginResizing( int resizeDir, MouseEvent e ) {}
 	protected void endResizing() {}
 
 	//---- interface PropertyChangeListener ----
@@ -370,7 +370,25 @@ public abstract class FlatWindowResizer
 		}
 
 		@Override
-		protected void beginResizing( int resizeDir ) {
+		protected void beginResizing( int resizeDir, MouseEvent e ) {
+			// on Linux, resize window using window manager
+			if( SystemInfo.isLinux && window != null && FlatNativeLinuxLibrary.isWMUtilsSupported( window ) ) {
+				int direction = -1;
+				switch( resizeDir ) {
+					case N_RESIZE_CURSOR:	direction = FlatNativeLinuxLibrary.SIZE_TOP; break;
+					case S_RESIZE_CURSOR:	direction = FlatNativeLinuxLibrary.SIZE_BOTTOM; break;
+					case W_RESIZE_CURSOR:	direction = FlatNativeLinuxLibrary.SIZE_LEFT; break;
+					case E_RESIZE_CURSOR:	direction = FlatNativeLinuxLibrary.SIZE_RIGHT; break;
+					case NW_RESIZE_CURSOR:	direction = FlatNativeLinuxLibrary.SIZE_TOPLEFT; break;
+					case NE_RESIZE_CURSOR:	direction = FlatNativeLinuxLibrary.SIZE_TOPRIGHT; break;
+					case SW_RESIZE_CURSOR:	direction = FlatNativeLinuxLibrary.SIZE_BOTTOMLEFT; break;
+					case SE_RESIZE_CURSOR:	direction = FlatNativeLinuxLibrary.SIZE_BOTTOMRIGHT; break;
+				}
+
+				if( direction >= 0 && FlatNativeLinuxLibrary.moveOrResizeWindow( window, e, direction ) )
+					return;
+			}
+
 			centerComp.setBounds( 0, 0, resizeComp.getWidth(), resizeComp.getHeight() );
 			centerComp.setCursor( getPredefinedCursor( resizeDir ) );
 			centerComp.setVisible( true );
@@ -462,7 +480,7 @@ public abstract class FlatWindowResizer
 		}
 
 		@Override
-		protected void beginResizing( int resizeDir ) {
+		protected void beginResizing( int resizeDir, MouseEvent e ) {
 			int direction = 0;
 			switch( resizeDir ) {
 				case N_RESIZE_CURSOR:	direction = NORTH; break;
@@ -581,7 +599,7 @@ debug*/
 			dragRightOffset = windowBounds.x + windowBounds.width - xOnScreen;
 			dragBottomOffset = windowBounds.y + windowBounds.height - yOnScreen;
 
-			beginResizing( resizeDir );
+			beginResizing( resizeDir, e );
 		}
 
 		@Override

flatlaf-core/src/main/resources/com/formdev/flatlaf/FlatLaf.properties

@@ -564,8 +564,8 @@ RadioButtonMenuItem.background = @menuBackground
 #---- RootPane ----
 
 RootPane.border = com.formdev.flatlaf.ui.FlatRootPaneUI$FlatWindowBorder
-RootPane.borderDragThickness = 5
+RootPane.borderDragThickness = 6
-RootPane.cornerDragWidth = 16
+RootPane.cornerDragWidth = 32
 RootPane.honorFrameMinimumSizeOnResize = false
 RootPane.honorDialogMinimumSizeOnResize = true
 

flatlaf-testing/dumps/uidefaults/FlatDarkLaf_1.8.0.txt

@@ -852,8 +852,8 @@ Resizable.resizeBorder         [lazy] 4,4,4,4  false    com.formdev.flatlaf.ui.F
 RootPane.activeBorderColor     #4d5154  HSL 206   4  32    com.formdev.flatlaf.util.DerivedColor [UI]    lighten(7% autoInverse)
 RootPane.background            #3c3f41  HSL 204   4  25    javax.swing.plaf.ColorUIResource [UI]
 RootPane.border                [lazy] 1,1,1,1  false    com.formdev.flatlaf.ui.FlatRootPaneUI$FlatWindowBorder [UI]
-RootPane.borderDragThickness   5
+RootPane.borderDragThickness   6
-RootPane.cornerDragWidth       16
+RootPane.cornerDragWidth       32
 RootPane.defaultButtonWindowKeyBindings length=8    [Ljava.lang.Object;
     [0] ENTER
     [1] press

flatlaf-testing/dumps/uidefaults/FlatLightLaf_1.8.0.txt

@@ -857,8 +857,8 @@ Resizable.resizeBorder         [lazy] 4,4,4,4  false    com.formdev.flatlaf.ui.F
 RootPane.activeBorderColor     #737373  HSL   0   0  45    com.formdev.flatlaf.util.DerivedColor [UI]    darken(50% autoInverse)
 RootPane.background            #f2f2f2  HSL   0   0  95    javax.swing.plaf.ColorUIResource [UI]
 RootPane.border                [lazy] 1,1,1,1  false    com.formdev.flatlaf.ui.FlatRootPaneUI$FlatWindowBorder [UI]
-RootPane.borderDragThickness   5
+RootPane.borderDragThickness   6
-RootPane.cornerDragWidth       16
+RootPane.cornerDragWidth       32
 RootPane.defaultButtonWindowKeyBindings length=8    [Ljava.lang.Object;
     [0] ENTER
     [1] press

flatlaf-testing/dumps/uidefaults/FlatMacDarkLaf_1.8.0.txt

@@ -861,8 +861,8 @@ Resizable.resizeBorder         [lazy] 4,4,4,4  false    com.formdev.flatlaf.ui.F
 RootPane.activeBorderColor     #303030  HSL   0   0  19    com.formdev.flatlaf.util.DerivedColor [UI]    lighten(7% autoInverse)
 RootPane.background            #1e1e1e  HSL   0   0  12    javax.swing.plaf.ColorUIResource [UI]
 RootPane.border                [lazy] 1,1,1,1  false    com.formdev.flatlaf.ui.FlatRootPaneUI$FlatWindowBorder [UI]
-RootPane.borderDragThickness   5
+RootPane.borderDragThickness   6
-RootPane.cornerDragWidth       16
+RootPane.cornerDragWidth       32
 RootPane.defaultButtonWindowKeyBindings length=8    [Ljava.lang.Object;
     [0] ENTER
     [1] press

flatlaf-testing/dumps/uidefaults/FlatMacLightLaf_1.8.0.txt

@@ -865,8 +865,8 @@ Resizable.resizeBorder         [lazy] 4,4,4,4  false    com.formdev.flatlaf.ui.F
 RootPane.activeBorderColor     #777777  HSL   0   0  47    com.formdev.flatlaf.util.DerivedColor [UI]    darken(50% autoInverse)
 RootPane.background            #f6f6f6  HSL   0   0  96    javax.swing.plaf.ColorUIResource [UI]
 RootPane.border                [lazy] 1,1,1,1  false    com.formdev.flatlaf.ui.FlatRootPaneUI$FlatWindowBorder [UI]
-RootPane.borderDragThickness   5
+RootPane.borderDragThickness   6
-RootPane.cornerDragWidth       16
+RootPane.cornerDragWidth       32
 RootPane.defaultButtonWindowKeyBindings length=8    [Ljava.lang.Object;
     [0] ENTER
     [1] press

flatlaf-testing/dumps/uidefaults/FlatTestLaf_1.8.0.txt

@@ -889,8 +889,8 @@ Resizable.resizeBorder         [lazy] 4,4,4,4  false    com.formdev.flatlaf.ui.F
 
 RootPane.background            #ccffcc  HSL 120 100  90    javax.swing.plaf.ColorUIResource [UI]
 RootPane.border                [lazy] 1,1,1,1  false    com.formdev.flatlaf.ui.FlatRootPaneUI$FlatWindowBorder [UI]
-RootPane.borderDragThickness   5
+RootPane.borderDragThickness   6
-RootPane.cornerDragWidth       16
+RootPane.cornerDragWidth       32
 RootPane.defaultButtonWindowKeyBindings length=8    [Ljava.lang.Object;
     [0] ENTER
     [1] press