Window Handles

After creating a window, the creation function returns a window handle that uniquely identifies the window. An application uses this handle in other functions to direct their actions to the window. A window handle has the HWND data type; an application must use this type when declaring a variable that holds a window handle.

The Win32 API includes several special constants that can replace a window handle in certain functions. For example, an application can use HWND_TOPMOST in the SendMessageTimeout function, HWND_BROADCAST in the SendMessage function, or HWND_DESKTOP in the MapWindowPoints function.

Although the NULL constant is not a window handle, you can use it in some functions to specify that no window is affected. For example, specifying NULL for the CreateWindowEx function's hwndParent parameter creates a window that has no parent or owner. Some functions may return NULL instead of a handle, indicating that the given action applies to no window.

An application can use the FindWindow function to discover whether a window with the specified class name or window name exists in the system. If such a window exists, FindWindow returns the handle of the window. To limit the search to the child windows of a particular application, use the FindWindowEx function. The IsWindow function determines whether a window handle identifies a valid, existing window.

Software for developers

Delphi Components
.Net Components
Software for Android Developers

More information resources

MegaDetailed.Net
Unix Manual Pages
Delphi Examples

Databases for Amazon shops developers

Amazon Categories Database
Browse Nodes Database