Dragging and dropping individual cels in the timeline to change their position is now possible.

Addresses a part of #306

CHANGELOG.md

@@ -12,6 +12,7 @@ Laurenz Reinthaler (Schweini07), kleonc, Variable-ind
 
 ### Added
 - A new pan tool, used to move around the canvas. ([#399](https://github.com/Orama-Interactive/Pixelorama/pull/399))
+- Dragging and dropping individual cels in the timeline to change their position is now possible.
 - Added a new "Performance" tab in the Preferences that exposes options related to the application's FPS to the user.
 - Added a new pixel grid, which is a grid of size 1px and it appears after a certain zoom level. ([#427](https://github.com/Orama-Interactive/Pixelorama/pull/427))
 - Added offset options to the grid. ([#434](https://github.com/Orama-Interactive/Pixelorama/pull/434))

src/Autoload/Global.gd

@@ -358,6 +358,9 @@ func undo(_frame_index := -1, _layer_index := -1, project : Project = current_pr
 			play_backwards.pressed = false
 			animation_timer.stop()
 
+	elif "Move Cels" == action_name:
+		project.frames = project.frames # to call frames_changed
+
 	canvas.update()
 	if !project.has_changed:
 		project.has_changed = true
@@ -388,6 +391,9 @@ func redo(_frame_index := -1, _layer_index := -1, project : Project = current_pr
 			play_backwards.pressed = false
 			animation_timer.stop()
 
+	elif "Move Cels" == action_name:
+		project.frames = project.frames # to call frames_changed
+
 	canvas.update()
 	if !project.has_changed:
 		project.has_changed = true

src/UI/Timeline/AnimationTimeline.gd

@@ -168,18 +168,21 @@ func _on_CopyFrame_pressed(frame := -1) -> void:
 func _on_FrameTagButton_pressed() -> void:
 	Global.tag_dialog.popup_centered()
 
+
 func _on_MoveLeft_pressed() -> void:
 	var frame : int = Global.current_project.current_frame
 	if frame == 0:
 		return
 	Global.current_project.layers[Global.current_project.current_layer].frame_container.get_child(frame).change_frame_order(-1)
 
+
 func _on_MoveRight_pressed() -> void:
 	var frame : int = Global.current_project.current_frame
 	if frame == last_frame:
 		return
 	Global.current_project.layers[Global.current_project.current_layer].frame_container.get_child(frame).change_frame_order(1)
 
+
 func _on_OnionSkinning_pressed() -> void:
 	Global.onion_skinning = !Global.onion_skinning
 	Global.canvas.update()
@@ -189,6 +192,7 @@ func _on_OnionSkinning_pressed() -> void:
 	else:
 		Global.change_button_texturerect(texture_button, "onion_skinning_off.png")
 
+
 func _on_OnionSkinningSettings_pressed() -> void:
 	$OnionSkinningSettings.popup(Rect2(Global.onion_skinning_button.rect_global_position.x - $OnionSkinningSettings.rect_size.x - 16, Global.onion_skinning_button.rect_global_position.y - 106, 136, 126))
 

src/UI/Timeline/CelButton.gd

@@ -107,6 +107,7 @@ func _on_PopupMenu_id_pressed(ID : int) -> void:
 				Global.frame_properties.set_frame_label(frame)
 				Global.frame_properties.set_frame_dur(Global.current_project.frames[frame].duration)
 
+
 func change_frame_order(rate : int) -> void:
 	var change = frame + rate
 	var new_frames : Array = Global.current_project.frames.duplicate()
@@ -126,3 +127,63 @@ func change_frame_order(rate : int) -> void:
 	Global.current_project.undo_redo.add_undo_method(Global, "undo")
 	Global.current_project.undo_redo.add_do_method(Global, "redo")
 	Global.current_project.undo_redo.commit_action()
+
+
+func get_drag_data(_position) -> Array:
+	var button := Button.new()
+	button.rect_size = rect_size
+	button.theme = Global.control.theme
+	var texture_rect := TextureRect.new()
+	texture_rect.rect_size = $CelTexture.rect_size
+	texture_rect.rect_position = $CelTexture.rect_position
+	texture_rect.expand = true
+	texture_rect.texture = $CelTexture.texture
+	button.add_child(texture_rect)
+	set_drag_preview(button)
+
+	return [frame, layer]
+
+
+func can_drop_data(_pos, data) -> bool:
+	if typeof(data) == TYPE_ARRAY:
+		var new_frame = data[0]
+		var new_layer = data[1]
+		if Global.current_project.frames[frame] in Global.current_project.layers[layer].linked_cels or Global.current_project.frames[new_frame] in Global.current_project.layers[new_layer].linked_cels:
+			# If the cel we're dragging or the cel we are targeting are linked, don't allow dragging
+			return false
+		else:
+			return true
+	else:
+		return false
+
+
+func drop_data(_pos, data) -> void:
+	var new_frame = data[0]
+	var new_layer = data[1]
+
+	var this_frame_new_cels = Global.current_project.frames[frame].cels.duplicate()
+	var new_frame_new_cels
+	var temp = this_frame_new_cels[layer]
+	this_frame_new_cels[layer] = Global.current_project.frames[new_frame].cels[new_layer]
+	if frame == new_frame:
+		this_frame_new_cels[new_layer] = temp
+	else:
+		new_frame_new_cels = Global.current_project.frames[new_frame].cels.duplicate()
+		new_frame_new_cels[new_layer] = temp
+
+	Global.current_project.undo_redo.create_action("Move Cels")
+	Global.current_project.undo_redo.add_do_property(Global.current_project.frames[frame], "cels", this_frame_new_cels)
+
+	if frame != new_frame: # If the cel moved to a different frame
+		Global.current_project.undo_redo.add_do_property(Global.current_project.frames[new_frame], "cels", new_frame_new_cels)
+
+		Global.current_project.undo_redo.add_do_property(Global.current_project, "current_frame", frame)
+		Global.current_project.undo_redo.add_undo_property(Global.current_project, "current_frame", Global.current_project.current_frame)
+
+		Global.current_project.undo_redo.add_undo_property(Global.current_project.frames[new_frame], "cels", Global.current_project.frames[new_frame].cels)
+
+	Global.current_project.undo_redo.add_undo_property(Global.current_project.frames[frame], "cels", Global.current_project.frames[frame].cels)
+
+	Global.current_project.undo_redo.add_undo_method(Global, "undo")
+	Global.current_project.undo_redo.add_do_method(Global, "redo")
+	Global.current_project.undo_redo.commit_action()