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• Event.java

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org.eclipse.swt.widgets.Event Maven / Gradle / Ivy

/*******************************************************************************
 * Copyright (c) 2000, 2022 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.swt.widgets;


import org.eclipse.swt.graphics.*;

/**
 * Instances of this class provide a description of a particular
 * event which occurred within SWT. The SWT untyped listener
 * API uses these instances for all event dispatching.
 * 

 * Note: For a given event, only the fields which are appropriate
 * will be filled in. The contents of the fields which are not used
 * by the event are unspecified.
 * 
 *
 * @see Listener
 * @see org.eclipse.swt.events.TypedEvent
 * @see SWT Example: ControlExample, Listeners
 * @see Sample code and further information
 */

public class Event {

	/**
	 * the display where the event occurred
	 *
	 * @since 2.0
	 */
	public Display display;

	/**
	 * the widget that issued the event
	 */
	public Widget widget;

	/**
	 * the type of event, as defined by the event type constants
	 * in class SWT
	 *
	 * @see org.eclipse.swt.SWT
	 */
	public int type;

	/**
	 * the event specific detail field, as defined by the detail constants
	 * in class SWT
	 *
	 * @see org.eclipse.swt.SWT
	 */
	public int detail;

	/**
	 * the item that the event occurred in (can be null)
	 */
	public Widget item;

	/**
	 * the index of the item where the event occurred
	 *
	 * @since 3.2
	 */
	public int index;

	/**
	 * the graphics context to use when painting
	 * that is configured to use the colors, font and
	 * damaged region of the control.  It is valid
	 * only during the paint and must not be disposed
	 */
	public GC gc;

	/**
	 * depending on the event type, the x offset of the bounding
	 * rectangle of the region that requires painting or the
	 * widget-relative, x coordinate of the pointer at the
	 * time the mouse button was pressed or released
	 */
	public int x;

	/**
	 * depending on the event type, the y offset of the bounding
	 * rectangle of the  region that requires painting or the
	 * widget-relative, y coordinate of the pointer at the
	 * time the mouse button was pressed or released
	 */
	public int y;

	/**
	 * the width of the bounding rectangle of the
	 * region that requires painting
	 */
	public int width;

	/**
	 * the height of the bounding rectangle of the
	 * region that requires painting
	 */
	public int height;

	/**
	 * depending on the event type, the number of following
	 * paint events that are pending which may always be zero
	 * on some platforms, or the number of lines or pages to
	 * scroll using the mouse wheel, or the number of times the
	 * mouse has been clicked
	 */
	public int count;

	/**
	 * the time that the event occurred.
	 *
	 * NOTE: This field is an unsigned integer and should
	 * be AND'ed with 0xFFFFFFFFL so that it can be treated
	 * as a signed long.
	 */
	public int time;

	/**
	 * the button that was pressed or released; 1 for the
	 * first button, 2 for the second button, and 3 for the
	 * third button, etc.
	 */
	public int button;

	/**
	 * depending on the event, the character represented by the key
	 * that was typed.  This is the final character that results
	 * after all modifiers have been applied.  For example, when the
	 * user types Ctrl+A, the character value is 0x01 (ASCII SOH).
	 * It is important that applications do not attempt to modify the
	 * character value based on a stateMask (such as SWT.CTRL) or the
	 * resulting character will not be correct.
	 */
	public char character;

	/**
	 * character that is good for keyboard shortcut comparison. Unlike
	 * {@link #character}, this tries to ignore modifier keys and deal
	 * with non-latin keyboard layouts.
	 * Examples:

	 * 
	 *  
	 *  
	 *  
	 *  
	 *  
	 *  
	 *  
	 *  
	 * 
Layout
US key label
character
keyCode
Windows English US    
C      
'c' 
 
'c'
Windows English US    
Shift+C
'C' 
 
'c'
Windows English US    
Ctrl+C 
0x03
'c'
Windows English Dvorak
I      
'c' 
'c'
Windows Bulgarian     
Ъ      
'ъ' 
'c'
Windows French        
2      
'é' 
'2'
Windows French        
Shift+2
'2' 
'2'


	 *
	 * How it is done differs per platform, and on many platforms,
	 * SWT resorts to various magic. To understand the problem,
	 * consider the following questions about the well known
	 * Ctrl+C shortcut:
	 * 

	 *  
Which key invokes Ctrl+C in English? Well, that's easy, key
	 *   C does it.
	 *  
Dvorak is basically an English layout, but with keys
	 *   shuffled around. Where English has C, Dvorak has J. Where
	 *   English has I, Dvorak has C. Which key invokes Ctrl+C in
	 *   English-Dvorak? Well, both answers are kind of correct.
	 *   There's a heated debate on the internet which answer is better:
	 *   some argue that they like English shortcuts they learned
	 *   before they decided to try Dvorak. Others argue that key
	 *   labels shall match invoked shortcuts. The usually preferred
	 *   answer is that if a key types C in Dvorak, then it shall
	 *   invoke Ctrl+C. That is, the key that is labeled I in English.
	 *  
Which key invokes Ctrl+C in non-latin keyboard layouts?
	 *   That's where it gets hard. Consider Hebrew, Cyrillic,
	 *   Japanese. These layouts simply don't have latin C anywhere!
	 * 
	 * Approaching all 3 questions at once is non-trivial, and each OS
	 * does it in a different way. In very simple words:
	 * 

	 *  
Windows keyboard layouts have an additional invisible
	 *   mapping of keys to keyboard shortcuts, completely independent
	 *   from characters typed by these keys. Layouts also have the
	 *   regular mapping of keys to produced characters. Both are
	 *   edited in keyboard layout editors.
	 *  
macOS keyboard layouts have hidden Latin sub-layouts and
	 *   switch to them when a modifier such as Cmd is pressed. This
	 *   is easy to see in builtin on-screen keyboard. It's a lot more
	 *   complicated with modifiers other than Cmd and Ctrl.
	 *  
Linux is worst. It lacks the information to map shortcuts
	 *   on non-latin keyboards and resorts to inspecting other
	 *   installed layouts to find something latin.
	 * 
	 *
	 * For detailed information, see {@link Widget#setKeyState} per
	 * platform.
	 *
	 *
	 * @see org.eclipse.swt.SWT
	 */
	/*
	 * For debugging, see
	 * 

	 *  
Unit tests Test_org_eclipse_swt_events_KeyEvent
	 *  
Files with names containing 'Issue0351_EventKeyCode'
	 * 
	 */
	public int keyCode;

	/**
	 * depending on the event, the location of key specified by the
	 * keyCode or character. The possible values for this field are
	 * SWT.LEFT, SWT.RIGHT, SWT.KEYPAD,
	 * or SWT.NONE representing the main keyboard area.
	 * 

	 * The location field can be used to differentiate key events that have
	 * the same key code and character but are generated by different keys
	 * in the keyboard. For example, a key down event with the key code equals
	 * to SWT.SHIFT can be generated by the left and the right shift keys in the
	 * keyboard. The location field can only be used to determine the location
	 * of the key code or character in the current event. It does not
	 * include information about the location of modifiers in state
	 * mask.
	 * 
	 *
	 * @see org.eclipse.swt.SWT#LEFT
	 * @see org.eclipse.swt.SWT#RIGHT
	 * @see org.eclipse.swt.SWT#KEYPAD
	 *
	 * @since 3.6
	 */
	public int keyLocation;

	/**
	 * depending on the event, the state of the keyboard modifier
	 * keys and mouse masks at the time the event was generated.
	 *
	 * @see org.eclipse.swt.SWT#MODIFIER_MASK
	 * @see org.eclipse.swt.SWT#BUTTON_MASK
	 */
	public int stateMask;

	/**
	 * depending on the event, the range of text being modified.
	 * Setting these fields only has effect during ImeComposition
	 * events.
	 */
	public int start, end;

	/**
	 * depending on the event, the new text that will be inserted.
	 * Setting this field will change the text that is about to
	 * be inserted or deleted.
	 */
	public String text;

	/**
	 * Bidi segment offsets
	 * @since 3.8
	 */
	public int[] segments;

	/**
	 * Characters to be applied on the segment boundaries
	 * @since 3.8
	 */
	public char[] segmentsChars;

	/**
	 * depending on the event, a flag indicating whether the operation
	 * should be allowed.  Setting this field to false will cancel the
	 * operation.
	 */
	public boolean doit = true;

	/**
	 * a field for application use
	 */
	public Object data;

	/**
	 * An array of the touch states for the current touch event.
	 *
	 * @since 3.7
	 */
	public Touch[] touches;

	/**
	 * If nonzero, a positive value indicates a swipe to the right,
	 * and a negative value indicates a swipe to the left.
	 *
	 * @since 3.7
	 */
	public int xDirection;

	/**
	 * If nonzero, a positive value indicates a swipe in the up direction,
	 * and a negative value indicates a swipe in the down direction.
	 *
	 * @since 3.7
	 */
	public int yDirection;

	/**
	 * The change in magnification. This value should be added to the current
	 * scaling of an item to get the new scale factor.
	 *
	 * @since 3.7
	 */
	public double magnification;

	/**
	 * The number of degrees rotated on the track pad.
	 *
	 * @since 3.7
	 */
	public double rotation;

/**
 * Gets the bounds.
 *
 * @return a rectangle that is the bounds.
 */
public Rectangle getBounds () {
	return new Rectangle (x, y, width, height);
}

Point getLocation () {
	return new Point (x, y);
}

/**
 * Sets the bounds.
 *
 * @param rect the new rectangle
 */
public void setBounds (Rectangle rect) {
	this.x = rect.x;
	this.y = rect.y;
	this.width = rect.width;
	this.height = rect.height;
}

void setLocation (int x, int y) {
	this.x = x;
	this.y = y;
}

/**
 * Returns a string containing a concise, human-readable
 * description of the receiver.
 *
 * @return a string representation of the event
 */
@Override
public String toString () {
	return "Event {type=" + type + " " + widget + " time=" + time + " data=" + data + " x=" + x + " y=" + y + " width=" + width + " height=" + height + " detail=" + detail + "}";  //$NON-NLS-1$//$NON-NLS-2$ //$NON-NLS-3$ //$NON-NLS-4$ //$NON-NLS-5$ //$NON-NLS-6$ //$NON-NLS-7$
}
}