Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Ask Question. Asked 10 years, 3 months ago. Active 10 years, 3 months ago. Viewed 13k times. Any ideas? Danpe Danpe Add a comment. Active Oldest Votes. David Heffernan k 40 40 gold badges silver badges bronze badges. Obviously you meant it to point to one of Raymond's articles.
I tried understanding the example on SendInput without any success.. I need to send Keys to a non focused proccess that is runing on my PC, and not from my keyboard, from a diffrent event, like button click.
Danpe, if the window isn't focused then SendInput wont' work. For more information about FindWindow function, please see the following link. For more information about PostMessage function, please see the following link. We are trying to better understand customer views on social support experience, so your participation in this interview project would be greatly appreciated if you have time. Thanks for helping make community forums a great place.
Click HERE to participate the survey. For more information, please see the following link. Send method, but you have to use SetForegroundWindow function, otherwise the window which in the background cannot receive this message. For more information about SendKeys. Send method, please refer to the following link. Could you provide some sort of explanation on the post message function? The website you provided doesn't give me nearly enough.
I mainly am confused on the last 3 parameters. What do the 3rd and fourth parameters do? A window procedure must check the message identifier to determine how to interpret the message parameters. The system sends or posts a system-defined message when it communicates with an application. It uses these messages to control the operations of applications and to provide input and other information for applications to process. An application can also send or post system-defined messages.
Applications generally use these messages to control the operation of control windows created by using preregistered window classes. Each system-defined message has a unique message identifier and a corresponding symbolic constant defined in the software development kit SDK header files that states the purpose of the message.
Symbolic constants specify the category to which system-defined messages belong. The prefix of the constant identifies the type of window that can interpret and process the message. Following are the prefixes and their related message categories. General window messages cover a wide range of information and requests, including messages for mouse and keyboard input, menu and dialog box input, window creation and management, and Dynamic Data Exchange DDE.
An application can create messages to be used by its own windows or to communicate with windows in other processes. If an application creates its own messages, the window procedure that receives them must interpret the messages and provide appropriate processing. The system uses two methods to route messages to a window procedure: posting messages to a first-in, first-out queue called a message queue , a system-defined memory object that temporarily stores messages, and sending messages directly to a window procedure.
A messages that is posted to a message queue is called a queued message. Most other messages, which are sent directly to a window procedure, are called nonqueued messages. The system can display any number of windows at a time. To route mouse and keyboard input to the appropriate window, the system uses message queues. The system maintains a single system message queue and one thread-specific message queue for each GUI thread.
To avoid the overhead of creating a message queue for non—GUI threads, all threads are created initially without a message queue. The system creates a thread-specific message queue only when the thread makes its first call to one of the specific user functions; no GUI function calls result in the creation of a message queue. Whenever the user moves the mouse, clicks the mouse buttons, or types on the keyboard, the device driver for the mouse or keyboard converts the input into messages and places them in the system message queue.
The system removes the messages, one at a time, from the system message queue, examines them to determine the destination window, and then posts them to the message queue of the thread that created the destination window. A thread's message queue receives all mouse and keyboard messages for the windows created by the thread. The thread removes messages from its queue and directs the system to send them to the appropriate window procedure for processing.
This ensures that a window receives its input messages in the proper first in, first out FIFO sequence. The system posts a message to a thread's message queue by filling an MSG structure and then copying it to the message queue. Information in MSG includes: the handle of the window for which the message is intended, the message identifier, the two message parameters, the time the message was posted, and the mouse cursor position.
A thread can post a message to its own message queue or to the queue of another thread by using the PostMessage or PostThreadMessage function. An application can remove a message from its queue by using the GetMessage function. To examine a message without removing it from its queue, an application can use the PeekMessage function. This function fills MSG with information about the message. After removing a message from its queue, an application can use the DispatchMessage function to direct the system to send the message to a window procedure for processing.
DispatchMessage passes the window handle, the message identifier, and the two message parameters to the window procedure, but it does not pass the time the message was posted or mouse cursor position. An application can retrieve this information by calling the GetMessageTime and GetMessagePos functions while processing a message. A thread can use the WaitMessage function to yield control to other threads when it has no messages in its message queue.
The function suspends the thread and does not return until a new message is placed in the thread's message queue. You can call the SetMessageExtraInfo function to associate a value with the current thread's message queue. Nonqueued messages are sent immediately to the destination window procedure, bypassing the system message queue and thread message queue. The system typically sends nonqueued messages to notify a window of events that affect it.
These messages notify the window that it has been activated, that keyboard input is being directed to the window, and that the mouse cursor has been moved within the borders of the window. Nonqueued messages can also result when an application calls certain system functions. An application must remove and process messages posted to the message queues of its threads.
A single-threaded application usually uses a message loop in its WinMain function to remove and send messages to the appropriate window procedures for processing. Applications with multiple threads can include a message loop in each thread that creates a window. The following sections describe how a message loop works and explain the role of a window procedure:. A simple message loop consists of one function call to each of these three functions: GetMessage , TranslateMessage , and DispatchMessage.
Note that if there is an error, GetMessage returns —1, thus the need for the special testing. In a single-threaded application, ending the message loop is often the first step in closing the application. If you specify a window handle as the second parameter of GetMessage , only messages for the specified window are retrieved from the queue.
GetMessage can also filter messages in the queue, retrieving only those messages that fall within a specified range. For more information about filtering messages, see Message Filtering. A thread's message loop must include TranslateMessage if the thread is to receive character input from the keyboard. A virtual-key message contains a virtual-key code that identifies which key was pressed, but not its character value.
The character message can then be removed upon a subsequent iteration of the message loop and dispatched to a window procedure. The DispatchMessage function sends a message to the window procedure associated with the window handle specified in the MSG structure. An application's main thread starts its message loop after initializing the application and creating at least one window. After it is started, the message loop continues to retrieve messages from the thread's message queue and to dispatch them to the appropriate windows.
Only one message loop is needed for a message queue, even if an application contains many windows. DispatchMessage always dispatches the message to the proper window; this is because each message in the queue is an MSG structure that contains the handle of the window to which the message belongs. You can modify a message loop in a variety of ways. For example, you can retrieve messages from the queue without dispatching them to a window.
This is useful for applications that post messages not specifying a window. You can also direct GetMessage to search for specific messages, leaving other messages in the queue.
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