public class DisplayList
This implements the Display and Paintable interfaces and provides a channel-like connection between user processes and an active graphics component.
The user process sees the Display<TT>Display</TT> interface to the DisplayList (in the same way as a writer process sees the OutputChannel interface to a Channel). The ActiveCanvas process sees the Paintable<TT>Paintable</TT> interface to the DisplayList (in the same way as a reader process sees the InputChannel interface to a Channel).
Unlike a Channel, however, a DisplayList should never block any of its attached processes indefinitely, regardless of the behaviour of its partner at the other end. The DisplayList imposes mutually exclusive access to its state and there are no wait/notify operations -- so any delays should be transient. User process sets/extends/changes and ActiveCanvas paints/updates on the DisplayList, therefore, should always succeed.
Note: the cautionary note in the above paragraph is because Java makes no guarantee that any invocation of a synchronized method ever takes place. This is something with which any Java application has to live.
Any number of user processes may draw on the same component via a DisplayList -- i.e. it is a any-one channel. By reserving different sections of a DisplayList for control by different processes, complex multiple animations can be simply managed.
Note: in this release, only the extend<TT>extend</TT> and change<TT>change</TT> methods are safe for direct use by multiple user processes on the same DisplayList. A process should only invoke set<TT>set</TT> at times when it knows others cannot be operating on that DisplayList. This would normally be required by an application, since a DisplayList reset invalidates the result returned by a previous extend and the base index used in a change -- i.e. concurrent processes doing these things will need to be informed before they do them again! However, if the list really needs concurrent setting without such an arrangement, this can be done within a synchronized block on the DisplayList.
User applications will not normally be implementing new processes that are at the receiving end of a DisplayList. Users will only be responsible for connecting a DisplayList to a standard org.jcsp.awt drawing component. This can either be done statically (e.g. through ActiveCanvas.setPaintable<TT>setPaintable</TT>) or dynamically (by sending a GraphicsProtocol.SetPaintable object through a GraphicsProtocol channel).
Type | Name and description |
---|---|
boolean |
change(GraphicsCommand[] c, int i) Changes the array of GraphicsCommands to be executed by replacing elements i onwards with the new ones. |
boolean |
change(GraphicsCommand c, int i) Changes the array of GraphicsCommands to be executed by replacing element i with the new one. |
int |
extend(GraphicsCommand[] c) Extends the array of GraphicsCommands to be executed. |
int |
extend(GraphicsCommand c) Extends the array of GraphicsCommands to be executed by one command. |
GraphicsCommand[] |
get() Returns a copy of the array of GraphicsCommands currently held. |
void |
paint(Graphics g) This is the call-back delegated here by the registered Component. |
void |
register(Component c) Register the Component that will delegate its paint and update methods here. |
void |
set(GraphicsCommand[] c) Sets the array of GraphicsCommands to be executed. |
void |
set(GraphicsCommand c) Sets the GraphicsCommand to be executed. |
void |
setMinRefreshInterval(long minRefreshInterval) Sets the repaint interval invoked by the set<TT>set</TT>, extend<TT>extend</TT> and change<TT>change</TT> commands. |
void |
update(Graphics g) This is the call-back delegated here by the registered Component. |
Changes the array of GraphicsCommands to be executed by replacing elements i onwards with the new ones. There must be at least (i + c.length) elements in the original array -- else this method will not change anything and will return false. The repaint method of the registered component is called to trigger the update<TT>update</TT> callback on this object. All commands will be executed.
c
- the new GraphicsCommands to be executed.i
- the start index for the replacement.Changes the array of GraphicsCommands to be executed by replacing element i with the new one. There must be at least (i + 1) elements in the original array -- else this method will not change anything and will return false. The repaint method of the registered component is called to trigger the update<TT>update</TT> callback on this object. All commands will be executed.
c
- the new GraphicsCommand to be executed.i
- the index for the replacement.Extends the array of GraphicsCommands to be executed. The repaint method of the registered component is called to trigger the update<TT>update</TT> callback on this object. Only the new commands will be executed.
c
- the extra GraphicsCommands to be executed.Extends the array of GraphicsCommands to be executed by one command. The repaint method of the registered component is called to trigger the update<TT>update</TT> callback on this object. Only the new command will be executed.
c
- the extra GraphicsCommand to be executed.Returns a copy of the array of GraphicsCommands currently held.
This is the call-back delegated here by the registered Component. It will normally be the JVM event thread that is making this call.
g
- the graphics context for the painting.Register the Component that will delegate its paint and update methods here. Only the JCSP Active component should perform this registration (in response to being passed this Paintable).
c
- the Component that will do the delegating.Sets the array of GraphicsCommands to be executed. The commands will be executed in ascending order of index. The repaint method of the registered component is called to trigger the update<TT>update</TT> callback on this object. All commands will be executed.
c
- the array of GraphicsCommands to be executed.Sets the GraphicsCommand to be executed. The repaint method of the registered component is called to trigger the update<TT>update</TT> callback on this object.
c
- the GraphicsCommand to be executed.Sets the repaint interval invoked by the set<TT>set</TT>, extend<TT>extend</TT> and change<TT>change</TT> commands. The default is 10 milliseconds (the normal default for the Component.repaint<TT>repaint</TT> method from Component).
minRefreshInterval
- the display commands will be executed at most once
per minRefreshInterval milliseconds.This is the call-back delegated here by the registered Component. It will normally be the JVM event thread that is making this call.
g
- the graphics context for the painting.