nankin.zheng.gatem.view
Class DisplayCacheImplSwing

java.lang.Object
  |
  +--nankin.zheng.gatem.view.DisplayCacheImplSwing

All Implemented Interfaces:

DisplayCache

public class DisplayCacheImplSwing

extends java.lang.Object

implements DisplayCache

A default implementation of interface DisplayCache as JPanel instance (for Swing-platform).

In Swing, the actual drawing is done by JPanel.paintComponent(), but in Gatem, the actual drawing is done by DisplayCache.flush(). So flush() should call JPanel.repaint() to update game frame, and JPanel.paintComponent() will draw game frame onto the screen according to the viewport and DrawCommand buffer.

Field Summary

private java.util.Vector	buffer Buffer saves all the draw commands.
private int	depth
private Env	env
private Position	viewport

Constructor Summary

DisplayCacheImplSwing(Env environ)
Constructor.

Method Summary

void	addToCache(DrawCommand cmd) Add a DrawCommand object to DrawCommand buffer.
void	flush(java.lang.Object helper) Flush buffer and draw the game frame onto the screen.
int	getDepth() Get depth.
private int	getViewportPhysicalX(DrawCommand cmd) Get physical coordonate x of the top-left point of the image contained in cmd.
private int	getViewportPhysicalY(DrawCommand cmd) Get physical coordonate y of the top-left point of the image contained in cmd.
private int	getWindowPhysicalX(int x) Adjust viewport physical coordonate x to window physical coordonate x.
private int	getWindowPhysicalY(int y) Adjust viewport physical coordonate y to window physical coordonate y.
private boolean	isInsideViewport(java.awt.Image img, int x, int y) Whether the image is inside the viewport.
void	setDepth(int d) Set depth
void	setViewport(Position vp) Set viewport position.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

env

private Env env

viewport

private Position viewport

depth

private int depth

buffer

private java.util.Vector buffer

Buffer saves all the draw commands. NOTICE that since JPanel.repaint() and g.drawImage() will create new threads to do the actual work, buffer should be visited mutually.

• While repaint()->paintComponent() is visiting buffer, buffer should not be modified by addToCache().
• While g.drawImage() is drawing images according to a certain order, the later image should wait until the previous one has been drawn completely.

Constructor Detail

DisplayCacheImplSwing

public DisplayCacheImplSwing(Env environ)

Constructor.

Parameters:

environ - game environment object.

Throws:

java.lang.NullPointerException - if environ is null.

Method Detail

getDepth

public int getDepth()

Get depth.

Specified by:

getDepth in interface DisplayCache

Returns:

depth

setDepth

public void setDepth(int d)

Set depth

Specified by:

setDepth in interface DisplayCache

Parameters:

d - depth to be set

setViewport

public void setViewport(Position vp)

Set viewport position. The viewport is the visual part of all the background.

Note that since DisplayCache.flush() is called by a thread, we CANNOT make sure that before another frame updating starts, the old DrawCommand instances have all been flushed. So, while setting viewport, it is possible that there are still some DrawCommand instances left in the buffer.

Specified by:

setViewport in interface DisplayCache

Parameters:

vp - position of viewport.

addToCache

public void addToCache(DrawCommand cmd)

Add a DrawCommand object to DrawCommand buffer.

While adding command to buffer, the image in the command is not drawn onto the screen but only saved in the buffer. All the draw commands will be executed (their images will be drawn onto the screen) for one time when flush() is called.

This method is set synchronized to avoid modifying buffer while buffer is being visited by paintComponent().

Specified by:

addToCache in interface DisplayCache

Parameters:

cmd - DrawCommand object.

Throws:

java.lang.NullPointerException - if cmd is null.

flush

public void flush(java.lang.Object helper)
           throws GameException

Flush buffer and draw the game frame onto the screen. After flushing, it will clean the buffer.

NOTE that this method does the actual drawing work, and it calls g.drawImage(Image, int, int) method. So this method will be called by JPanel.paintComponent() method.

NOTE that this method is set synchronized to prevent other method (addToCache()) from modifying the buffer while it is in use.

Specified by:

flush in interface DisplayCache

Parameters:

helper - Graphics object, containing the drawing environment.

Throws:

GameException - if helper is not an instance of Graphics.

getViewportPhysicalX

private int getViewportPhysicalX(DrawCommand cmd)

Get physical coordonate x of the top-left point of the image contained in cmd.

Parameters:

cmd - DrawCommand object which contains the image and the logical coordonate of the image.

Returns:

physical coordonate x of the top-left point of the image.

getViewportPhysicalY

private int getViewportPhysicalY(DrawCommand cmd)

Get physical coordonate y of the top-left point of the image contained in cmd.

Parameters:

cmd - DrawCommand object which contains the image and the logical coordonate of the image.

Returns:

physical coordonate y of the top-left point of the image.

getWindowPhysicalX

private int getWindowPhysicalX(int x)

Adjust viewport physical coordonate x to window physical coordonate x.

getWindowPhysicalY

private int getWindowPhysicalY(int y)

Adjust viewport physical coordonate y to window physical coordonate y.

isInsideViewport

private boolean isInsideViewport(java.awt.Image img,
                                 int x,
                                 int y)

Whether the image is inside the viewport.

Parameters:

img - image.

x - physical coordonate x of the top-left point of the image.

y - physical coordonate y of the top-left point of the image.

Returns:

true if the image is inside the viewport.