com.diffplug.common.swt

Class SwtExec

java.lang.Object

java.util.concurrent.AbstractExecutorService

com.diffplug.common.swt.SwtExec

All Implemented Interfaces:

com.diffplug.common.rx.RxExecutor.Has, Executor, ExecutorService, ScheduledExecutorService

public class SwtExec
extends AbstractExecutorService
implements ScheduledExecutorService, com.diffplug.common.rx.RxExecutor.Has

Executors which execute on the SWT UI thread. There are two primary kinds of `SwtExec`: - async() -> performs actions using Display.asyncExec - immediate() -> performs actions immediately if called from a UI thread, otherwise delegates to `asyncExec`. In addition to the standard executor methods, each `SwtExec` also has a method guardOn, which returns a SwtExec.Guarded instance - the cure for "Widget is disposed" errors. `Guarded` is an Executor and RxSubscriber which stops running tasks and cancels all subscriptions and futures when the guard widget is disposed. ```java SwtExec.immediate().guardOn(myWidget).subscribe(someFuture, value -> myWidget.setContentsTo(value)); ``` In the example above, if the widget is disposed before the future completes, that's fine! No "widget is disposed" errors. blocking() is similar to `async()` and `immediate()`, but it doesn't support `guard` - it's just a simple `Executor`. It performs actions immediately if called from a UI thread, else delegates to the blocking Display.syncExec(java.lang.Runnable). It also has the SwtExec.Blocking.get(Supplier) method, which allows you to easily get a value using a function which must be called on the SWT thread. In the rare scenario where you need higher performance, it is possible to get similar behavior as immediate() but with less overhead (and safety) in swtOnly() and sameThread(). It is very rarely worth this sacrifice.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	SwtExec.Blocking An Executor (obtained via blocking()) which adds a blocking get() method.
static class	SwtExec.Guarded Executor and Rx for conducting actions which are guarded on an SWT widget.

Field Summary

Fields

Modifier and Type	Field and Description
protected com.diffplug.common.rx.RxExecutor	rxExecutor

Method Summary

Modifier and Type	Method and Description
static SwtExec	async() Returns an "async" SwtExecutor.
boolean	awaitTermination(long timeout, TimeUnit unit) Deprecated.
static SwtExec.Blocking	blocking() Returns a "blocking" Executor for the SWT thread.
void	execute(Runnable runnable) Executes the given command at some time in the future.
com.diffplug.common.rx.RxExecutor	getRxExecutor() Returns an instance of RxExecutor.
SwtExec.Guarded	guardOn(com.diffplug.common.rx.Chit chit) Returns an API for performing actions which are guarded on the given Widget.
SwtExec.Guarded	guardOn(ControlWrapper wrapper) Returns an API for performing actions which are guarded on the given ControlWrapper.
SwtExec.Guarded	guardOn(Widget widget) Returns an API for performing actions which are guarded on the given Widget.
static SwtExec	immediate() Returns an "immediate" SwtExecutor.
static boolean	isRunningOnUI() Returns true iff called from the UI thread.
boolean	isShutdown() Deprecated.
boolean	isTerminated() Deprecated.
static SwtExec	sameThread() UNLESS YOU HAVE PERFORMANCE PROBLEMS, USE immediate() INSTEAD.
<V> ScheduledFuture<V>	schedule(Callable<V> callable, long delay, TimeUnit unit) Creates and executes a ScheduledFuture that becomes enabled after the given delay.
ScheduledFuture<?>	schedule(Runnable command, long delay, TimeUnit unit) Creates and executes a one-shot action that becomes enabled after the given delay.
ScheduledFuture<?>	scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit) Creates and executes a periodic action that becomes enabled first after the given initial delay, and subsequently with the given period; that is executions will commence after initialDelay then initialDelay+period, then initialDelay + 2 * period, and so on.
ScheduledFuture<?>	scheduleWithFixedDelay(Runnable command, long initialDelay, long delay, TimeUnit unit) Creates and executes a periodic action that becomes enabled first after the given initial delay, and subsequently with the given delay between the termination of one execution and the commencement of the next.
void	shutdown() Deprecated.
List<Runnable>	shutdownNow() Deprecated.
static SwtExec	swtOnly() UNLESS YOU HAVE PERFORMANCE PROBLEMS, USE immediate() INSTEAD.
static void	timerExec(int ms, Runnable runnable) Executes the given runnable in the UI thread after the given delay.

Methods inherited from class java.util.concurrent.AbstractExecutorService

invokeAll, invokeAll, invokeAny, invokeAny, newTaskFor, newTaskFor, submit, submit, submit

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.concurrent.ExecutorService

invokeAll, invokeAll, invokeAny, invokeAny, submit, submit, submit

Field Detail

rxExecutor

protected final com.diffplug.common.rx.RxExecutor rxExecutor

Method Detail

isRunningOnUI

public static boolean isRunningOnUI()

Returns true iff called from the UI thread.

async

public static SwtExec async()

Returns an "async" SwtExecutor.

When `execute(Runnable)` is called, the `Runnable` will be passed to Display.asyncExec.

immediate

public static SwtExec immediate()

Returns an "immediate" SwtExecutor. - When `execute(Runnable)` is called from the SWT thread, the `Runnable` will be executed immediately. - Else, the `Runnable` will be passed to Display.asyncExec. In the rare case that `immediate()` only ever receives events on the SWT thread, there are faster options: - swtOnly is about 3x faster, and will throw an error if you call it from somewhere besides an SWT thread. - sameThread is about 15x faster, and will not throw an error if you call it from somewhere besides an SWT thread (but your callback probably will). It is very rare that sacrificing the safety of `immediate()` is worth it. Here is the approximate throughput of the three options on a Win 10, i7-2630QM machine. - `immediate()` - 2.9 million events per second - `swtOnly()` - 8.3 million events per second - `sameThread()` - 50 million events per second

blocking

public static SwtExec.Blocking blocking()

Returns a "blocking" Executor for the SWT thread.

• When `execute(Runnable)` is called from the SWT thread, the `Runnable` will be executed immediately.
• Else, the `Runnable` will be passed to Display.syncExec.

This instance also has a blocking get() method for doing a get in the UI thread.

timerExec

public static void timerExec(int ms,
                             Runnable runnable)

Executes the given runnable in the UI thread after the given delay.

guardOn

public SwtExec.Guarded guardOn(com.diffplug.common.rx.Chit chit)

Returns an API for performing actions which are guarded on the given Widget.

guardOn

public SwtExec.Guarded guardOn(Widget widget)

Returns an API for performing actions which are guarded on the given Widget.

guardOn

public SwtExec.Guarded guardOn(ControlWrapper wrapper)

Returns an API for performing actions which are guarded on the given ControlWrapper.

getRxExecutor

public com.diffplug.common.rx.RxExecutor getRxExecutor()

Returns an instance of RxExecutor.

Specified by:

getRxExecutor in interface com.diffplug.common.rx.RxExecutor.Has

execute

public void execute(Runnable runnable)

Executes the given command at some time in the future. The command may execute in a new thread, in a pooled thread, or in the calling thread, at the discretion of the Executor implementation.

Specified by:

execute in interface Executor

Parameters:

runnable - the runnable task

Throws:

RejectedExecutionException - if this task cannot be accepted for execution.

NullPointerException - if command is null

shutdown

@Deprecated
public void shutdown()

Deprecated.

Initiates an orderly shutdown in which previously submitted tasks are executed, but no new tasks will be accepted. Invocation has no additional effect if already shut down.

Specified by:

shutdown in interface ExecutorService

Throws:

SecurityException - if a security manager exists and shutting down this ExecutorService may manipulate threads that the caller is not permitted to modify because it does not hold RuntimePermission("modifyThread"), or the security manager's checkAccess method denies access.

shutdownNow

@Deprecated
public List<Runnable> shutdownNow()

Deprecated.

Attempts to stop all actively executing tasks, halts the processing of waiting tasks, and returns a list of the tasks that were awaiting execution.

There are no guarantees beyond best-effort attempts to stop processing actively executing tasks. For example, typical implementations will cancel via Thread.interrupt(), so any task that fails to respond to interrupts may never terminate.

Specified by:

shutdownNow in interface ExecutorService

Returns:

list of tasks that never commenced execution

Throws:

SecurityException - if a security manager exists and shutting down this ExecutorService may manipulate threads that the caller is not permitted to modify because it does not hold RuntimePermission("modifyThread"), or the security manager's checkAccess method denies access.

isShutdown

@Deprecated
public boolean isShutdown()

Deprecated.

Returns true if this executor has been shut down.

Specified by:

isShutdown in interface ExecutorService

Returns:

true if this executor has been shut down

isTerminated

@Deprecated
public boolean isTerminated()

Deprecated.

Returns true if all tasks have completed following shut down. Note that isTerminated is never true unless either shutdown or shutdownNow was called first.

Specified by:

isTerminated in interface ExecutorService

Returns:

true if all tasks have completed following shut down

awaitTermination

@Deprecated
public boolean awaitTermination(long timeout,
                                            TimeUnit unit)
                                     throws InterruptedException

Deprecated.

Blocks until all tasks have completed execution after a shutdown request, or the timeout occurs, or the current thread is interrupted, whichever happens first.

Specified by:

awaitTermination in interface ExecutorService

Parameters:

timeout - the maximum time to wait

unit - the time unit of the timeout argument

Returns:

true if this executor terminated and false if the timeout elapsed before termination

Throws:

InterruptedException - if interrupted while waiting

schedule

public ScheduledFuture<?> schedule(Runnable command,
                                   long delay,
                                   TimeUnit unit)

Creates and executes a one-shot action that becomes enabled after the given delay.

Specified by:

schedule in interface ScheduledExecutorService

Parameters:

command - the task to execute

delay - the time from now to delay execution

unit - the time unit of the delay parameter

Returns:

a ScheduledFuture representing pending completion of the task and whose get() method will return null upon completion

Throws:

RejectedExecutionException - if the task cannot be scheduled for execution

NullPointerException - if command is null

schedule

public <V> ScheduledFuture<V> schedule(Callable<V> callable,
                                       long delay,
                                       TimeUnit unit)

Creates and executes a ScheduledFuture that becomes enabled after the given delay.

Specified by:

schedule in interface ScheduledExecutorService

Parameters:

callable - the function to execute

delay - the time from now to delay execution

unit - the time unit of the delay parameter

Returns:

a ScheduledFuture that can be used to extract result or cancel

Throws:

RejectedExecutionException - if the task cannot be scheduled for execution

NullPointerException - if callable is null

scheduleAtFixedRate

public ScheduledFuture<?> scheduleAtFixedRate(Runnable command,
                                              long initialDelay,
                                              long period,
                                              TimeUnit unit)

Creates and executes a periodic action that becomes enabled first after the given initial delay, and subsequently with the given period; that is executions will commence after initialDelay then initialDelay+period, then initialDelay + 2 * period, and so on. If any execution of the task encounters an exception, subsequent executions are suppressed. Otherwise, the task will only terminate via cancellation or termination of the executor. If any execution of this task takes longer than its period, then subsequent executions may start late, but will not concurrently execute.

Specified by:

scheduleAtFixedRate in interface ScheduledExecutorService

Parameters:

command - the task to execute

initialDelay - the time to delay first execution

period - the period between successive executions

unit - the time unit of the initialDelay and period parameters

Returns:

a ScheduledFuture representing pending completion of the task, and whose get() method will throw an exception upon cancellation

Throws:

RejectedExecutionException - if the task cannot be scheduled for execution

NullPointerException - if command is null

IllegalArgumentException - if period less than or equal to zero

scheduleWithFixedDelay

public ScheduledFuture<?> scheduleWithFixedDelay(Runnable command,
                                                 long initialDelay,
                                                 long delay,
                                                 TimeUnit unit)

Creates and executes a periodic action that becomes enabled first after the given initial delay, and subsequently with the given delay between the termination of one execution and the commencement of the next. If any execution of the task encounters an exception, subsequent executions are suppressed. Otherwise, the task will only terminate via cancellation or termination of the executor.

Specified by:

scheduleWithFixedDelay in interface ScheduledExecutorService

Parameters:

command - the task to execute

initialDelay - the time to delay first execution

delay - the delay between the termination of one execution and the commencement of the next

unit - the time unit of the initialDelay and delay parameters

Returns:

a ScheduledFuture representing pending completion of the task, and whose get() method will throw an exception upon cancellation

Throws:

RejectedExecutionException - if the task cannot be scheduled for execution

NullPointerException - if command is null

IllegalArgumentException - if delay less than or equal to zero

swtOnly

public static SwtExec swtOnly()

UNLESS YOU HAVE PERFORMANCE PROBLEMS, USE immediate() INSTEAD. Returns an SwtExecutor which can only be called from the SWT thread, and runs actions immediately. Has the same behavior as immediate() for callbacks on the SWT thread. For values not on the SWT thread, `immediate()` behaves likes async(), while `swtOnly()` throws an exception.

sameThread

public static SwtExec sameThread()

UNLESS YOU HAVE PERFORMANCE PROBLEMS, USE immediate() INSTEAD. Returns an SwtExec which runs actions immediately, without checking whether they were called from the SWT thread or not.