For more information about using the GetSysColor function to access the COLOR_ACTIVE-CAPTION and COLOR_INACTIVE-CAPTION constants, see the documentation included in the Win32 SDK.
While the system supports the display of multiple windows, the user generally works within a single window at a time. This window is called the active window. The active window is typically at the top of the window Z order. It is also visually distinguished by its title bar that is displayed in the active window title color. All other windows are inactive with respect to the user's input; that is, while other windows can have ongoing processes, only the active window receives the user's input. The title bar of an inactive window displays the system inactive window color. Your application can query the system for the current values for the active title bar color and the inactive title bar color.
Note
For more information about using the GetSysColor function to access the COLOR_ACTIVE-CAPTION and COLOR_INACTIVE-CAPTION constants, see the documentation included in the Win32 SDK.
The user activates a primary window by switching to it; this inactivates any other primary windows. To activate a window with the mouse or pen, the user clicks or taps on any part of the window, including its interior. If the window is minimized, the user clicks (taps) the button representing the window in the taskbar. From the keyboard, the system provides the ALT+TAB key combination for switching between primary windows. The SHIFT+ALT+TAB key also switches between windows, but in reverse order. (The system also supports ALT+ESC for switching between windows.) The reactivation of a window should not affect any pre-existing selection within it; the selection and focus are restored to the previously active state.
When the user reactivates a primary window, the window and all its secondary windows come to the top of the window order and maintain their relative positions. If the user activates a secondary window, its primary window comes to the top of the window order along with the primary window's other secondary windows.
When a window becomes inactive, hide the selection feedback (for example, display of highlighting or handles) of any selection within it to prevent confusion over which window is receiving keyboard input. A direct manipulation transfer (drag and drop) is an exception. Here, you can display transfer feedback if the pointer is over the window during the drag operation. Do not activate the window unless the user releases the mouse button (the pen tip is lifted) in that window.