Scroll across multiple monitors

Use the virtual space extents instead of primary screen.

desk.go

@@ -9,6 +9,7 @@ type Desktop interface {
 	RecentApps() []AppData
 	Settings() DeskSettings
 	ContentBoundsPixels(*Screen) (x, y, w, h uint32)
+	RootSizePixels() (w, h uint32)
 	Screens() ScreenList
 
 	IconProvider() ApplicationProvider

internal/ui/desk.go

@@ -52,14 +52,17 @@ func (l *desktop) SetDesktop(id int) {
 	diff := id - l.desk
 	l.desk = id
 
-	display := l.Screens().Primary() // TODO need to iterate/find full virtual height
-	off := float32(diff*-display.Height) / display.Scale
+	_, height := l.RootSizePixels()
+	offPix := float32(diff * -int(height))
 	wins := l.wm.Windows()
 
 	starts := make([]fyne.Position, len(wins))
 	deltas := make([]fyne.Delta, len(wins))
 	for i, win := range wins {
 		starts[i] = win.Position()
+
+		display := l.Screens().ScreenForWindow(win)
+		off := offPix / display.Scale
 		deltas[i] = fyne.NewDelta(0, off)
 	}
 
@@ -193,6 +196,22 @@ func (l *desktop) ContentBoundsPixels(screen *fynedesk.Screen) (x, y, w, h uint3
 	return 0, 0, screenW, screenH
 }
 
+func (l *desktop) RootSizePixels() (w, h uint32) {
+	for _, screen := range l.Screens().Screens() {
+		right := uint32(screen.X + screen.Width)
+		bottom := uint32(screen.Y + screen.Height)
+
+		if right > w {
+			w = right
+		}
+		if bottom > h {
+			h = bottom
+		}
+	}
+
+	return w, h
+}
+
 func (l *desktop) IconProvider() fynedesk.ApplicationProvider {
 	return l.icons
 }

internal/x11/win/client.go

@@ -129,8 +129,10 @@ func (c *client) SetDesktop(id int) {
 	diff := id - c.desk
 	c.desk = id
 
-	display := d.Screens().Primary() // TODO need to iterate/find full virtual height
-	off := float32(diff*display.Height) / display.Scale
+	_, height := d.RootSizePixels()
+	offPix := float32(diff * -int(height))
+	display := d.Screens().ScreenForWindow(c)
+	off := offPix / display.Scale
 
 	start := c.Position()
 	fyne.NewAnimation(canvas.DurationStandard, func(f float32) {

test/desktop.go

@@ -45,7 +45,11 @@ func (*Desktop) Capture() image.Image {
 
 // ContentBoundsPixels returns a default value for how much space maximised apps should use
 func (*Desktop) ContentBoundsPixels(_ *fynedesk.Screen) (x, y, w, h uint32) {
-	return 0, 0, uint32(320), uint32(240)
+	return 0, 0, 320, 240
+}
+
+func (*Desktop) RootSizePixels() (w, h uint32) {
+	return 320, 240
 }
 
 // Desktop returns the index of the current desktop (in test this is always 0)