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# QMdiSubWindow Class Reference
[com.trolltech.qt.gui module]

The `QMdiSubWindow` class provides a subwindow class for `QMdiArea`. More...

Inherits `QWidget`.

## Detailed Description

The `QMdiSubWindow` class provides a subwindow class for `QMdiArea`.

`QMdiSubWindow` represents a top-level window in a `QMdiArea`, and consists of a title bar with window decorations, an internal widget, and (depending on the current style) a window frame and a size grip. `QMdiSubWindow` has its own layout, which consists of the title bar and a center area for the internal widget.

The most common way to construct a `QMdiSubWindow` is to call QMdiArea::addSubWindow() with the internal widget as the argument. You can also create a subwindow yourself, and set an internal widget by calling `setWidget`.

You use the same API when programming with subwindows as with regular top-level windows (e.g., you can call functions such as `show`, `hide`, `showMaximized`, and `setWindowTitle`).

### Subwindow Handling

`QMdiSubWindow` also supports behavior specific to subwindows in an MDI area.

By default, each `QMdiSubWindow` is visible inside the MDI area viewport when moved around, but it is also possible to specify transparent window movement and resizing behavior, where only the outline of a subwindow is updated during these operations. The `setOption` function is used to enable this behavior.

The `isShaded` function detects whether the subwindow is currently shaded (i.e., the window is collapsed so that only the title bar is visible). To enter shaded mode, call `showShaded`. `QMdiSubWindow` emits the `windowStateChanged` signal whenever the window state has changed (e.g., when the window becomes minimized, or is restored). It also emits `aboutToActivate` before it is activated.

In keyboard-interactive mode, the windows are moved and resized with the keyboard. You can enter this mode through the system menu of the window. The `keyboardSingleStep` and `keyboardPageStep` properties control the distance the widget is moved or resized for each keypress event. When shift is pressed down page step is used; otherwise single step is used.

See also `QMdiArea`.