Add support forward and back mouse buttons

Author: akiyosi

editor/window.go

@@ -3057,6 +3057,10 @@ func (w *Window) mouseEvent(event *gui.QMouseEvent) {
 			bt = core.Qt__RightButton
 		} else if event.Buttons()&core.Qt__MidButton > 0 {
 			bt = core.Qt__MidButton
+		} else if event.Buttons()&core.Qt__XButton1 > 0 {
+			bt = core.Qt__XButton1
+		} else if event.Buttons()&core.Qt__XButton2 > 0 {
+			bt = core.Qt__XButton2
 		}
 	}
 
@@ -3068,6 +3072,10 @@ func (w *Window) mouseEvent(event *gui.QMouseEvent) {
 		button += "right"
 	case core.Qt__MidButton:
 		button += "middle"
+	case core.Qt__XButton1:
+		button += "x1"
+	case core.Qt__XButton2:
+		button += "x2"
 	case core.Qt__NoButton:
 	default:
 	}