DragReorderHandler.java

/*
 * Copyright 2016 Laszlo Balazs-Csiki
 *
 * This file is part of Pixelitor. Pixelitor is free software: you
 * can redistribute it and/or modify it under the terms of the GNU
 * General Public License, version 3 as published by the Free
 * Software Foundation.
 *
 * Pixelitor is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Pixelitor. If not, see <http://www.gnu.org/licenses/>.
 */

package pixelitor.layers;

import javax.swing.*;
import javax.swing.event.MouseInputAdapter;
import java.awt.Component;
import java.awt.Cursor;
import java.awt.event.MouseEvent;

/**
 * The MouseListener and MouseMotionListener for the layer buttons for the drag-reordering
 */
public class DragReorderHandler extends MouseInputAdapter {
    private static final Cursor MOVE_CURSOR = Cursor.getPredefinedCursor(Cursor.HAND_CURSOR);
    private static final Cursor DEFAULT_CURSOR = Cursor.getDefaultCursor();
    private static final int DRAG_X_INDENT = 10;
    private final LayersPanel layersPanel;
    private int dragStartYInButton;
    private boolean dragging = false;
    private long lastNameEditorPressesMillis;

    public DragReorderHandler(LayersPanel layersPanel) {
        this.layersPanel = layersPanel;
    }

    @Override
    public void mousePressed(MouseEvent e) {
        // a manual double-click watch - necessary on Mac?
        Component c = e.getComponent();
        if (c instanceof LayerNameEditor) {
            long when = e.getWhen();
            long diffMillis = when - lastNameEditorPressesMillis;
            if (diffMillis < 250) {
                LayerNameEditor editor = (LayerNameEditor) c;
                editor.enableEditing();
            }
            lastNameEditorPressesMillis = when;
        }

        getLayerButtonFromEvent(e); // the call is necessary for translating the mouse event
        dragStartYInButton = e.getY();
    }

    @Override
    public void mouseDragged(MouseEvent e) {
        LayerButton layerButton = getLayerButtonFromEvent(e);
        if (!dragging && Math.abs(dragStartYInButton - e.getY()) < 5) {
            // it seems that on Mac we get mouseDragged events even when the mouse is not moved
            return;
        }
        if (layerButton.isNameEditing()) {
            return;
        }

        // since the LayerButton is continuously relocated, e.getY() returns
        // the mouse relative to the last LayerButton position
        int newY = layerButton.getY() + e.getY() - dragStartYInButton;
        layerButton.setLocation(DRAG_X_INDENT, newY);

        layersPanel.updateDrag(layerButton, newY, !dragging);
        dragging = true;

        layerButton.setCursor(MOVE_CURSOR);
        layersPanel.doLayout();
    }

    @Override
    public void mouseReleased(MouseEvent e) {
        LayerButton layerButton = getLayerButtonFromEvent(e);
        if (dragging) {
            layerButton.setCursor(DEFAULT_CURSOR);
            layersPanel.dragFinished();
        } else {
            // necessary on Mac so that the layer gets selected
            // even if the user clicks on the name field
            layerButton.setSelected(true);
        }
        dragging = false;
    }

    /**
     * Returns the layer button for the mouse event and also translate
     * the coordinates of the argument into the layer button space
     */
    private static LayerButton getLayerButtonFromEvent(MouseEvent e) {
        LayerButton layerButton;
        Component c = e.getComponent();
        // the source of the event must be either the layer button
        // or the textfield inside it
        if (c instanceof LayerNameEditor) {
            LayerNameEditor nameEditor = (LayerNameEditor) c;
            layerButton = nameEditor.getLayerButton();
            // translate into the LayerButton coordinate system
            e.translatePoint(nameEditor.getX(), nameEditor.getY());
        } else if (c instanceof JLabel) {
            layerButton = (LayerButton) c.getParent();
            e.translatePoint(c.getX(), c.getY());
        } else {
            layerButton = (LayerButton) c;
        }
        return layerButton;
    }

    public void attachToComponent(Component c) {
        c.addMouseListener(this);
        c.addMouseMotionListener(this);
    }

    public void detachFromComponent(Component c) {
        c.addMouseListener(this);
        c.addMouseMotionListener(this);
    }
}