scratch-paint/src/helper/selection-tools/select-tool.js

import Modes from '../../modes/modes';

import {getHoveredItem} from '../hover';
import {deleteSelection, selectRootItem} from '../selection';
import BoundingBoxTool from './bounding-box-tool';
import SelectionBoxTool from './selection-box-tool';
import paper from 'paper';

/**
 * paper.Tool that handles select mode. This is made up of 2 subtools.
 * - The selection box tool is active when the user clicks an empty space and drags.
 *   It selects all items in the rectangle.
 * - The bounding box tool is active if the user clicks on a non-empty space. It handles
 *   reshaping the item that was clicked.
 */
class SelectTool extends paper.Tool {
    /** The distance within which mouse events count as a hit against an item */
    static get TOLERANCE () {
        return 6;
    }
    /**
     * @param {function} setHoveredItem Callback to set the hovered item
     * @param {function} clearHoveredItem Callback to clear the hovered item
     * @param {!function} onUpdateSvg A callback to call when the image visibly changes
     */
    constructor (setHoveredItem, clearHoveredItem, onUpdateSvg) {
        super();
        this.setHoveredItem = setHoveredItem;
        this.clearHoveredItem = clearHoveredItem;
        this.onUpdateSvg = onUpdateSvg;
        this.boundingBoxTool = new BoundingBoxTool(onUpdateSvg);
        this.selectionBoxTool = new SelectionBoxTool(Modes.SELECT);
        this.selectionBoxMode = false;
        this.prevHoveredItemId = null;
        
        // We have to set these functions instead of just declaring them because
        // paper.js tools hook up the listeners in the setter functions.
        this.onMouseDown = this.handleMouseDown;
        this.onMouseMove = this.handleMouseMove;
        this.onMouseDrag = this.handleMouseDrag;
        this.onMouseUp = this.handleMouseUp;
        this.onKeyUp = this.handleKeyUp;

        selectRootItem();
        this.boundingBoxTool.setSelectionBounds();
    }
    /**
     * To be called when the hovered item changes. When the select tool hovers over a
     * new item, it compares against this to see if a hover item change event needs to
     * be fired.
     * @param {paper.Item} prevHoveredItemId ID of the highlight item that indicates the mouse is
     *     over a given item currently
     */
    setPrevHoveredItemId (prevHoveredItemId) {
        this.prevHoveredItemId = prevHoveredItemId;
    }
    /**
     * Returns the hit options to use when conducting hit tests.
     * @param {boolean} preselectedOnly True if we should only return results that are already
     *     selected.
     * @return {object} See paper.Item.hitTest for definition of options
     */
    getHitOptions (preselectedOnly) {
        // Tolerance needs to be scaled when the view is zoomed in in order to represent the same
        // distance for the user to move the mouse.
        const hitOptions = {
            segments: true,
            stroke: true,
            curves: true,
            fill: true,
            guide: false,
            tolerance: SelectTool.TOLERANCE / paper.view.zoom
        };
        if (preselectedOnly) {
            hitOptions.selected = true;
        }
        return hitOptions;
    }
    handleMouseDown (event) {
        if (event.event.button > 0) return; // only first mouse button

        // If bounding box tool does not find an item that was hit, use selection box tool.
        this.clearHoveredItem();
        if (!this.boundingBoxTool
            .onMouseDown(
                event,
                event.modifiers.alt,
                event.modifiers.shift,
                this.getHitOptions(false /* preseelectedOnly */))) {
            this.selectionBoxMode = true;
            this.selectionBoxTool.onMouseDown(event.modifiers.shift);
        }
    }
    handleMouseMove (event) {
        const hoveredItem = getHoveredItem(event, this.getHitOptions());
        if ((!hoveredItem && this.prevHoveredItemId) || // There is no longer a hovered item
                (hoveredItem && !this.prevHoveredItemId) || // There is now a hovered item
                (hoveredItem && this.prevHoveredItemId &&
                    hoveredItem.id !== this.prevHoveredItemId)) { // hovered item changed
            this.setHoveredItem(hoveredItem ? hoveredItem.id : null);
        }
    }
    handleMouseDrag (event) {
        if (event.event.button > 0) return; // only first mouse button

        if (this.selectionBoxMode) {
            this.selectionBoxTool.onMouseDrag(event);
        } else {
            this.boundingBoxTool.onMouseDrag(event);
        }
    }
    handleMouseUp (event) {
        if (event.event.button > 0) return; // only first mouse button

        if (this.selectionBoxMode) {
            this.selectionBoxTool.onMouseUp(event);
            this.boundingBoxTool.setSelectionBounds();
        } else {
            this.boundingBoxTool.onMouseUp(event);
        }
        this.selectionBoxMode = false;
    }
    handleKeyUp (event) {
        // Backspace, delete
        if (event.key === 'delete' || event.key === 'backspace') {
            deleteSelection(Modes.SELECT);
            this.clearHoveredItem();
            this.boundingBoxTool.removeBoundsPath();
            this.onUpdateSvg();
        }
    }
    deactivateTool () {
        this.clearHoveredItem();
        this.boundingBoxTool.removeBoundsPath();
        this.setHoveredItem = null;
        this.clearHoveredItem = null;
        this.onUpdateSvg = null;
        this.boundingBoxTool = null;
        this.selectionBoxTool = null;
    }
}

export default SelectTool;