fix(windows): recalculate hit-test regions on DPI change for frameless windows

When a frameless transparent window is moved between monitors with
different DPI settings, the hit-test regions weren't being recalculated,
causing the right and bottom edges to become unresponsive to clicks.

This fix adds the SWP_FRAMECHANGED flag to SetWindowPos in the
WM_DPICHANGED handler for frameless windows, which triggers
WM_NCCALCSIZE to recalculate the non-client area and hit-test regions.

For frameless windows with decorations, the DWM frame is also
re-extended into the client area to ensure proper window frame
styling after the DPI change.

Fixes #4691

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: leaanthony

v3/UNRELEASED_CHANGELOG.md

@@ -23,6 +23,7 @@ After processing, the content will be moved to the main changelog and this file
 
 ## Fixed
 <!-- Bug fixes -->
+- Fix frameless transparent window hit-test regions not updating after DPI change on Windows (#4691)
 
 ## Deprecated
 <!-- Soon-to-be removed features -->

v3/pkg/application/webview_window_windows.go

@@ -1584,13 +1584,27 @@ func (w *windowsWebviewWindow) WndProc(msg uint32, wparam, lparam uintptr) uintp
 	case w32.WM_DPICHANGED:
 		if !w.ignoreDPIChangeResizing {
 			newWindowRect := (*w32.RECT)(unsafe.Pointer(lparam))
+			flags := w32.SWP_NOZORDER | w32.SWP_NOACTIVATE
+			// For frameless windows, include SWP_FRAMECHANGED to trigger WM_NCCALCSIZE
+			// and recalculate hit-test regions for proper mouse interaction after DPI change.
+			// See: https://github.com/wailsapp/wails/issues/4691
+			if w.parent.options.Frameless {
+				flags |= w32.SWP_FRAMECHANGED
+			}
 			w32.SetWindowPos(w.hwnd,
 				uintptr(0),
 				int(newWindowRect.Left),
 				int(newWindowRect.Top),
 				int(newWindowRect.Right-newWindowRect.Left),
 				int(newWindowRect.Bottom-newWindowRect.Top),
-				w32.SWP_NOZORDER|w32.SWP_NOACTIVATE)
+				flags)
+			// For frameless windows with decorations, re-extend the frame into client area
+			// to ensure proper window frame styling after DPI change.
+			if w.framelessWithDecorations() {
+				if err := w32.ExtendFrameIntoClientArea(w.hwnd, true); err != nil {
+					globalApplication.handleFatalError(err)
+				}
+			}
 		}
 		w.parent.emit(events.Windows.WindowDPIChanged)
 	}