app: [Windows] suppress double-click behaviour for custom decorations

Fixes: https://todo.sr.ht/~eliasnaur/gio/600
Signed-off-by: Elias Naur <mail@eliasnaur.com>

app/internal/windows/windows.go

@@ -266,6 +266,7 @@ const (
 	WM_MOUSEWHEEL           = 0x020A
 	WM_MOUSEHWHEEL          = 0x020E
 	WM_NCACTIVATE           = 0x0086
+	WM_NCLBUTTONDBLCLK      = 0x00A3
 	WM_NCHITTEST            = 0x0084
 	WM_NCCALCSIZE           = 0x0083
 	WM_PAINT                = 0x000F

app/os_wayland.go

@@ -1633,6 +1633,14 @@ func (w *window) flushScroll() {
 	if total == (f32.Point{}) {
 		return
 	}
+	if w.scroll.steps == (image.Point{}) {
+		w.fling.xExtrapolation.SampleDelta(w.scroll.time, -w.scroll.dist.X)
+		w.fling.yExtrapolation.SampleDelta(w.scroll.time, -w.scroll.dist.Y)
+	}
+	// Zero scroll distance prior to calling ProcessEvent, otherwise we may recursively
+	// re-process the scroll distance.
+	w.scroll.dist = f32.Point{}
+	w.scroll.steps = image.Point{}
 	w.ProcessEvent(pointer.Event{
 		Kind:      pointer.Scroll,
 		Source:    pointer.Mouse,
@@ -1642,12 +1650,6 @@ func (w *window) flushScroll() {
 		Time:      w.scroll.time,
 		Modifiers: w.disp.xkb.Modifiers(),
 	})
-	if w.scroll.steps == (image.Point{}) {
-		w.fling.xExtrapolation.SampleDelta(w.scroll.time, -w.scroll.dist.X)
-		w.fling.yExtrapolation.SampleDelta(w.scroll.time, -w.scroll.dist.Y)
-	}
-	w.scroll.dist = f32.Point{}
-	w.scroll.steps = image.Point{}
 }
 
 func (w *window) onPointerMotion(x, y C.wl_fixed_t, t C.uint32_t) {

app/os_windows.go

@@ -326,6 +326,12 @@ func windowProc(hwnd syscall.Handle, msg uint32, wParam, lParam uintptr) uintptr
 		mi := windows.GetMonitorInfo(w.hwnd)
 		szp.Rgrc[0] = mi.WorkArea
 		return 0
+	case windows.WM_NCLBUTTONDBLCLK:
+		if !w.config.Decorated {
+			// Override Windows behaviour when we
+			// draw decorations.
+			return 0
+		}
 	case windows.WM_PAINT:
 		w.draw(true)
 	case windows.WM_SIZE: