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// This Source Code is Copyright & Licenced as indicated below package org.litesoft.GWT.client.widgets.nonpublic.external; /* * Copyright 2007 Mat Gessel <mat.gessel@gmail.com> * * Licensed under the Apache License, Version 2.0 (the "License"); you may not * use this file except in compliance with the License. You may obtain a copy of * the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the * License for the specific language governing permissions and limitations under * the License. */ /** * A DragGesture wrapper which prevents the wrapped gesture's step action * from occuring until a specified distance is exceeded. This can be used to * prevent accidental manipulation or to pervent the wrapped gesture's start * action from being executed until the mouse is moved. */ public class DragThresholdFilter extends DragGestureWrapper { private final int m_threshold; private MouseEvent m_start; private boolean m_started = false; /** * Creates a new DragGesture with the specified threshold. * * @param distance the distance in screen pixels to move before taking an * action, or <code>0</code> */ public DragThresholdFilter( int distance, DragGesture delegate ) { super( delegate ); if ( distance < 0 ) { throw new IllegalArgumentException( String.valueOf( distance ) ); } m_threshold = distance; } protected boolean equalsThreshold( int deltaX, int deltaY ) { return Math.abs( deltaX ) >= m_threshold || Math.abs( deltaY ) >= m_threshold; } @Override public void start( MouseEvent e ) { if ( m_threshold == 0 ) { m_started = true; super.start( e ); } else { m_start = e; } } @Override public void step( DragEvent e ) { if ( !m_started && equalsThreshold( e.getDeltaX(), e.getDeltaY() ) ) { m_started = true; super.start( m_start ); } if ( m_started ) { super.step( e ); } } @Override public void finish() { super.finish(); m_started = false; m_start = null; } } |