Handling Clicks Inside a Scrollcontainer in Godot

Handling Clicks Inside a ScrollContainer in Godot

The Issue with Clickable Items Inside a ScrollContainer

When working with ScrollContainer in Godot, a common issue arises when interactive elements inside the container use the InputEventMouseButton event with the pressed state. This can cause unintended interactions, where a scroll gesture is mistakenly interpreted as a click. The problem stems from the fact that the ScrollContainer responds to mouse motion, but individual UI elements also listen for clicks, leading to ambiguous behavior.

A typical scenario occurs when a user attempts to scroll through the ScrollContainer by clicking and dragging. If a clickable item inside the container is connected to the mouse_pressed event, the system may register a click even when the user intended to scroll.

The Solution: Tracking Drag Distance

To differentiate between a deliberate click and a scrolling gesture, we can track the distance between the initial mouse_pressed position and the mouse_released position. If the distance exceeds a predefined threshold, we assume that scrolling occurred, and we ignore the click event. Otherwise, if the movement is within the threshold, we process the click normally.

Below is an improved version of the code following Godot’s GDScript conventions:

extends Control

var drag_start_position: Vector2
var is_dragging: bool = false
const DRAG_THRESHOLD: float = 10.0  # Adjust as needed

func _on_card_menu_gui_input(event: InputEvent, scene_index: int) -> void:
    if event is InputEventMouseButton and event.button_index == MOUSE_BUTTON_LEFT:
        if event.pressed:
            drag_start_position = event.position
            is_dragging = false
        else:
            if not is_dragging:
                _load_puzzle_scene(scene_index)
    elif event is InputEventMouseMotion:
        if event.position.distance_to(drag_start_position) > DRAG_THRESHOLD:
            is_dragging = true

Explanation of the Code

1. Tracking Drag Start Position: When the left mouse button is pressed, we store the initial mouse position (drag_start_position) and assume no dragging is happening (is_dragging = false).
2. Handling Mouse Release: If the user releases the mouse button and is_dragging is still false, we consider it a valid click and load the new scene.
3. Detecting Dragging: If the user moves the mouse while pressing it down, we calculate the distance from the initial position. If it exceeds DRAG_THRESHOLD, we set is_dragging = true, preventing the click action from triggering.

Why This Works

By implementing a distance threshold, we prevent scroll gestures from triggering unintended clicks. This solution ensures smooth scrolling while still allowing users to interact with clickable items inside the ScrollContainer without misfires.

By refining input handling in this way, you can create a more user-friendly interface and avoid common pitfalls associated with UI interaction in Godot.