fix(desktop): restore maximized window dragged by the caption

Dragging the custom Windows title bar while the window is maximized kept
calling setLocation against the maximized bounds, so the window stayed
pinned instead of following the pointer until the user restored it by
double-clicking. The drag handler now clears MAXIMIZED_BOTH on the first
drag event and re-anchors the window under the pointer at the same
relative position, matching native Windows behavior.

Author: HandSonic

chat2db-community-server/chat2db-community-jcef/src/main/java/ai/chat2db/community/jcef/frame/WindowsCommunityWindowChrome.java

@@ -6,6 +6,7 @@
 import javax.swing.JRootPane;
 import javax.swing.SwingUtilities;
 import java.awt.Component;
+import java.awt.Dimension;
 import java.awt.Frame;
 import java.awt.Point;
 import java.awt.event.InputEvent;
@@ -67,6 +68,23 @@ static Point draggedWindowLocation(Point windowOrigin, Point pointerOrigin, Poin
         );
     }
 
+    /**
+     * Native Windows behavior when a maximized window is dragged: restore it
+     * and place it so the pointer stays at the same relative position inside
+     * the window, instead of leaving it pinned against the maximized bounds.
+     */
+    static Point restoredDragOrigin(Dimension maximizedSize, Dimension restoredSize,
+            Point windowOrigin, Point pointerScreen) {
+        double ratioX = maximizedSize.width <= 0 ? 0.5
+                : (double) (pointerScreen.x - windowOrigin.x) / maximizedSize.width;
+        double ratioY = maximizedSize.height <= 0 ? 0.5
+                : (double) (pointerScreen.y - windowOrigin.y) / maximizedSize.height;
+        return new Point(
+                pointerScreen.x - (int) Math.round(ratioX * restoredSize.width),
+                pointerScreen.y - (int) Math.round(ratioY * restoredSize.height)
+        );
+    }
+
     private static final class BrowserWindowDragHandler extends MouseAdapter {
 
         private final Frame frame;
@@ -96,7 +114,14 @@ public void mouseDragged(MouseEvent event) {
                     || (event.getModifiersEx() & InputEvent.BUTTON1_DOWN_MASK) == 0) {
                 return;
             }
-            frame.setLocation(draggedWindowLocation(windowOrigin, pointerOrigin, event.getLocationOnScreen()));
+            Point pointer = event.getLocationOnScreen();
+            if ((frame.getExtendedState() & Frame.MAXIMIZED_BOTH) == Frame.MAXIMIZED_BOTH) {
+                Dimension maximizedSize = frame.getSize();
+                frame.setExtendedState(frame.getExtendedState() & ~Frame.MAXIMIZED_BOTH);
+                windowOrigin = restoredDragOrigin(maximizedSize, frame.getSize(), windowOrigin, pointer);
+                pointerOrigin = pointer;
+            }
+            frame.setLocation(draggedWindowLocation(windowOrigin, pointerOrigin, pointer));
         }
 
         @Override

chat2db-community-server/chat2db-community-jcef/src/test/java/ai/chat2db/community/jcef/frame/WindowsCommunityWindowChromeTest.java

@@ -6,6 +6,7 @@
 import javax.swing.JComponent;
 import javax.swing.JPanel;
 import javax.swing.JRootPane;
+import java.awt.Dimension;
 import java.awt.Point;
 import java.util.function.Function;
 
@@ -78,4 +79,33 @@ void shouldMoveWindowByThePointerDelta() {
                 )
         );
     }
+
+    @Test
+    void shouldAnchorRestoredWindowUnderThePointer() {
+        // Maximized 1000x800 at (0,0); the drag started with the pointer a
+        // quarter across and 5% down. After restoring to 800x600 the window
+        // must jump so the pointer keeps that relative position.
+        assertEquals(
+                new Point(250 - 200, 40 - 30),
+                WindowsCommunityWindowChrome.restoredDragOrigin(
+                        new Dimension(1000, 800),
+                        new Dimension(800, 600),
+                        new Point(0, 0),
+                        new Point(250, 40)
+                )
+        );
+    }
+
+    @Test
+    void shouldFallBackToCenterAnchorsWhenMaximizedSizeIsUnknown() {
+        assertEquals(
+                new Point(600 - 400, 300 - 300),
+                WindowsCommunityWindowChrome.restoredDragOrigin(
+                        new Dimension(0, 0),
+                        new Dimension(800, 600),
+                        new Point(0, 0),
+                        new Point(600, 300)
+                )
+        );
+    }
 }