Drag and drop layer/frame/cel buttons on touchscreens when they are pressed

Otherwise scroll the timeline

Author: OverloadedOrama

src/UI/Timeline/CelButton.gd

@@ -273,7 +273,7 @@ func _dim_checker() -> void:
 
 
 func _get_drag_data(_position: Vector2) -> Variant:
-	if DisplayServer.is_touchscreen_available():
+	if DisplayServer.is_touchscreen_available() and not button_pressed:
 		return null
 	var button := Button.new()
 	button.size = size

src/UI/Timeline/FrameButton.gd

@@ -110,7 +110,7 @@ func _on_PopupMenu_id_pressed(id: int) -> void:
 
 
 func _get_drag_data(_position: Vector2) -> Variant:
-	if DisplayServer.is_touchscreen_available():
+	if DisplayServer.is_touchscreen_available() and not button_pressed:
 		return null
 	var button := Button.new()
 	button.size = size

src/UI/Timeline/FrameScrollContainer.gd

@@ -120,18 +120,23 @@ func _gui_input(event: InputEvent) -> void:
 				):
 					h_scroll_bar.value -= PAGE_DIVISOR * event.factor
 					accept_event()
-				elif (
+					return
+				if (
 					event.button_index == MOUSE_BUTTON_WHEEL_DOWN
 					or event.button_index == MOUSE_BUTTON_WHEEL_RIGHT
 				):
 					h_scroll_bar.value += PAGE_DIVISOR * event.factor
 					accept_event()
+					return
 	_touchscreen_scroll(event)
 
 
 func _touchscreen_scroll(event: InputEvent) -> void:
 	if not DisplayServer.is_touchscreen_available():
 		return
+	if get_viewport().gui_is_dragging() and not scroll_on_drag_hover:
+		_cancel_drag()
+		return
 	var prev_h_scroll := h_scroll_bar.value
 	# Handle mouse button input
 	if event is InputEventMouseButton:

src/UI/Timeline/LayerMainButton.gd

@@ -12,7 +12,7 @@ func _ready() -> void:
 
 
 func _get_drag_data(_position: Vector2) -> Variant:
-	if DisplayServer.is_touchscreen_available():
+	if DisplayServer.is_touchscreen_available() and not button_pressed:
 		return null
 	var layers := _get_layer_indices()
 	for layer_i in layers:  # Add child layers, if we have selected groups