Important: You have to remember that only one global hook can exist at a time since calling SetDispatchProc will override the previously set one.

Additionally, UioHook contains the PostEvent method for simulating input events.

UioHook also contains the PostText method which simulates text entry. The text to simulate doesn't depend on the current keyboard layout. The full range of UTF-16 (including surrogate pairs, e.g. emojis) is supported.

libuiohook also provides functions to get various system properties. The corresponding methods are also present in UioHook.

Global Hooks

SharpHook provides the IGlobalHook interface along with three default implementations which you can use to control the hook and subscribe to its events. Here's a basic usage example:

First, you create the hook, then subscribe to its events, and then run it. The Run method runs the hook on the current thread, blocking it. The RunAsync() method runs the hook on a separate thread and returns a Task which is finished when the hook is stopped. You can subscribe to events after the hook is started.

IGlobalHook contains the Stop method to stop the global hook. After stopping, the global hook can be started again by calling the Run or RunAsync method. Calling Stop when the hook is not running won't do anything.

IGlobalHook extends IDisposable. When you call the Dispose method on a hook, it's disposed and stopped if it was running. Once a hook has been disposed, it cannot be started again – you'll have to create a new instance. Calling Dispose when the hook is not running won't do anything other than marking the instance as disposed.

Hook events are of type HookEventArgs or a derived type which contains more info. It's possible to suppress event propagation by setting the SuppressEvent property to true inside the event handler. This must be done synchronously and is only supported on Windows and macOS. You can check the event time and whether the event is real or simulated with the EventTime and IsEventSimulated properties respectively.

Important: Always use one instance of IGlobalHook at a time in the entire application since they all must use the same static method to set the hook callback for libuiohook, so there may only be one callback at a time. Running a global hook when another global hook is already running will corrupt the internal global state of libuiohook.

You can create a keyboard-only or a mouse-only hook by passing a GlobalHookType to the hook's constructor. This makes a real difference only on Windows where there are two different global hooks – a keyboard hook and a mouse hook. On macOS and Linux, there is one hook for all events, and this simply enables filtering keyboard or mouse events out on these OSes.

SharpHook provides three implementations of IGlobalHook:

• SharpHook.SimpleGlobalHook runs all of its event handlers on the same thread on which the hook itself runs. This means that the handlers should generally be fast since they will block the hook from handling the events that follow if they run for too long.

• SharpHook.EventLoopGlobalHook runs all of its event handlers on a separate dedicated thread. On backpressure it will queue the remaining events which means that the hook will be able to process all events. This implementation should be preferred to SimpleGlobalHook except for very simple use-cases. But it has a downside – suppressing event propagation will be ignored since event handlers are run on another thread.

• SharpHook.TaskPoolGlobalHook runs all of its event handlers on other threads inside the default thread pool for tasks. The parallelism level of the handlers can be configured. On backpressure it will queue the remaining events which means that the hook will be able to process all events. This implementation should be preferred to SimpleGlobalHook except for very simple use-cases. But it has a downside – suppressing event propagation will be ignored since event handlers are run on other threads. In general, EventLoopGlobalHook should be preferred instead, as this class provides benefits only if events should be processed in parallel, which is rarely the case.

The library also provides the SharpHook.GlobalHookBase class which you can extend to create your own implementation of the global hook. It calls the appropriate event handlers, and you only need to implement a strategy for dispatching the events. It also keeps a reference to a running global hook so that it's not garbage-collected.

Reactive Global Hooks

Use the SharpHook.Reactive package for reactive global hooks with Rx.NET integration.

Use the SharpHook.R3 package for reactive global hooks with R3 integration.

Event Simulation

SharpHook provides the ability to simulate keyboard and mouse events in a cross-platform way as well. Here's a quick example:

SharpHook provides the IEventSimulator interface, and the default implementation, EventSimulator, which by default calls UioHook.PostEvent to simulate the events.

Text Entry Simulation

SharpHook also provides text entry simulation. IEventSimulator contains the SimulateTextEntry method which accepts a string. The text to simulate doesn't depend on the current keyboard layout. The full range of UTF-16 (including surrogate pairs, e.g., emojis) is supported.

Logging

libuiohook can log messages throughout its execution. By default the messages are not logged anywhere, but you can get these logs by using the ILogSource interface and its default implementation, LogSource:

ILogSource extends IDisposable – you can dispose of a log source to stop receiving libuiohook messages.

An EmptyLogSource class is also available – this class doesn't listen to the libuiohook logs and can be used instead of LogSource in release builds.

Testing

SharpHook provides two classes which make testing easier. They aren't required since mocks can be used instead, but unlike mocks, no setup is required to use these classes.

SharpHook.Testing.TestGlobalHook provides an implementation of IGlobalHook and IEventSimulator which can be used for testing. When the Run or RunAsync method is called, it will dispatch events using the various Simulate methods from IEventSimulator.

If this class is used as an IEventSimulator in the tested code, then the SimulatedEvents property can be checked to see which events were simulated using the test instance.

If the low-level functionality of SharpHook should be mocked, or mocking should be pushed as far away as possible, then SharpHook.Testing.TestProvider can be used. It implements every interface in the SharpHook.Providers namespace and as such it can be used instead of a normal low-level functionality provider.

Like TestGlobalHook, this class can post events using the PostEvent method and dispatch them if Run was called. It also contains the PostedEvents property.

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