Переключение окон с помощью клавиатуры: Alt+Tab и принцип работы

Keyboard shortcut to switch windows without using a mouse

is the common name for a keyboard shortcut that has been in Microsoft Windows since Windows 2.0 (1987). This shortcut switches between application level windows without using the mouse; hence it was named Task Switcher (Flip in Windows Vista). orders windows by most recently used, thus repeated keystrokes will switch between the two most recent tasks. It can also be used alternate between a full size window and the desktop. The window environment maintains a Z order list of top level windows (tasks) with the most recently used tasks at the front and the desktop at the bottom, so the most recently used tasks can be switched to the most quickly. The keyboard combination has also been incorporated in other operating systems and desktop environments such as KDE, Xfce, and GNOME. iOS and macOS have similar functionality by pressing but that switches applications rather than windows.

Windows may be divided into two categories, 'always on top' and ordinary. When a task is switched to, it is moved to the head of its category. For the following example, suppose there are no 'always on top' windows. Let A be the current window title. Hold down Alt and press and release Tab once, leaving Alt pressed. The window list comes up. A is guaranteed to be first in the list. Suppose the complete list is A W Z E U B C. The selection cursor will initially be on W. Suppose we want to switch to window U. Without releasing Alt, press Tab three more times and then release Alt. Then hold down Alt and press release Tab once leaving Alt down. The window list will now show U A W Z E B C. Then Tab over to E and release Alt, selecting window E. Press and hold down Alt and press release Tab once leaving Alt down. The window list will now show E U A W Z B C. Note that the windows switched to with (E, U, A) are in order of how recently they were switched to. Now Tab over to A and release Alt. Press and hold down Alt and press release Tab leaving Alt down. The window list will show A E U W Z B C. The effect of this most recently used behavior is that to return to the most recent task, Tab is pressed once, for the second most recent task Tab is pressed twice, and so on for all tasks. The priority of a window in terms of accessibility is how recently it was used. If A is now minimized, the list will become E U W Z B C A, and if Z is minimized the list becomes E U W B C A Z. Thus minimizing a window mimics the effect of not using it for a long time. The commonplace alternation between the 2 most recent tasks (using a fast with all keys released immediately) is precisely a special case of the above behavior. Suppose the windows are A B C and we want to alternate between A and B. Hold Alt while pressing and releasing Tab; continue holding Alt. The list will show A B C and the cursor will initially be over B. When Alt is released B will be selected, Tab having been pressed a total of 1 time, and zero attention to the task selection cursor having been necessary. Again, press and release Tab while holding Alt. The list will show B A C and the cursor will initially be over A. When Alt is released we have switched back to A. Displaying the list again, the order has returned to A B C and this sequence can recur. On close inspection, in the course of typing and releasing both keys quickly, the task list window can be observed to flicker for a split second, so If the user has been switching among 3 applications and wants to dispense with one of them by minimizing, one of the remaining ones will be on top immediately after minimizing, and ordinarily will alternate between the 2 remaining windows. If a program fails to move to the end of the list when minimized, pressing once will return to the minimized program. Failures such as this can result in a frenzied reordering of the list by means of several sequences to compensate for the program misbehavior. The algorithm for this reshuffling is intuitive after using for a long time. If the user attempts to switch to an application using but the application fails to update its place in the z order (for example, if its window procedure is hung), then the next time is invoked, the task selection cursor may initially point unexpectedly far into the list of icons, just past the application in question, which will not have been moved to the head of the list. Applications have some say in where they are located in the order. The list of windows is altered by the creation and destruction of windows, programmatic hiding, showing, raising, and lowering of windows, and alterations to the window z order
The order of the list corresponds directly to the z order, once the windows have been sorted according to 'always on top' status. Alt Shift Esc is equivalent to one Alt Shift Tab except that minimized windows are selected without being displayed.

Similar functionality exists on macOS using instead of , and switching between applications rather than windows. The Mac's switcher has the additional capabilities of pointing at the desired icon with the mouse (also present in Windows Vista and above), and dropping files on applications' icons. Selected application can be hidden or closed using or keys without closing the menu. works similarly to switch between windows within the same application. Once has been invoked, changes behavior to mimic (i. e. it cycles backwards). Using or allows the user to select the window to focus on. The and arrow keys may also be used to navigate the application switcher. This functionality does not automatically restore windows from an application in which all windows been minimized. To restore a window, one needs to press as many times as necessary to choose the desired application, and hold the Option key just prior to releasing the Command button. This will restore the most relevant window in the application. There was no default key binding for application switching in Classic Mac OS. Third party control panels (such as ApplWindows and LiteSwitch) provided this behavior.

iOS adds comparable functionality using instead of , as with macOS. The iOS switcher allows the user to move between recently used applications (nine in landscape, six in portrait), as opposed to "open" applications, since the concept of an open application is considerably less clear on iOS than other desktop operating systems. cycles backwards, as in OS X.

Unix like desktop systems such as fvwm, KDE, Xfce, and GNOME have added a compatible function. On some systems including Sun's CDE and old versions of fvwm, the key combination is mapped to less sophisticated functionality such as only alternating between two windows, cycling forward or backward in a list of all windows in a fixed order, or opening a task applet in which one has to use arrow keys or the mouse to select a task and then click or push Enter. Some window managers such as WindowLab forego the onscreen window list and simply bring each window to the front in turn as is pressed. Not all window managers provide this functionality as a core feature. For example, Blackbox does not; users desiring this behavior can add it by running a helper application such as bbkeys.

Compiz Fusion (aka Beryl, Compiz) has similar functionality, but displays a preview of the window as well as its icon (Present in Windows Vista and above, with DWM enabled). It also makes use of Alt Shift Tab by moving backwards through the displayed programs, and it is possible to activate a Windows Flip 3D alternative using the Windows key and Tab.

The Metacity window manager has similar functionality to versions of Windows released before Vista, but it only displays the outline of the currently selected window on the screen. Windows, on the other hand shows the whole selected window, which helps the user to pick the correct window from multiple windows with a similar title or icon.

The key combination to switch between windows has been present in all versions of Windows since Windows 1.0. However, there was no visual indication of the list of windows available when switching between windows until Windows 3.1, when this feature was introduced as the 'Fast "Alt+TAB" Switching' checkbox in the Display control panel applet, internally known as "CoolSwitch". Before CoolSwitch, the combination was similar to the combination (which also switched windows), but redrew each window immediately on each stroke, while brought the windows to the top but did not redraw them until the Alt key was released.

An example of a program that violates the expectation that pressing one time will switch to the previous application is Adobe Reader 7.0. x. Like newer versions of Microsoft Word it attempts to give a separate icon in the task menu to each MDI document. However, unlike Word, it brings two items to the front of the list whenever a document is selected using : first an icon representing the main Reader window and then an icon for the individual document. While in Adobe Reader, pressing one time selects the second item in the list, which is the icon for the PDF document. Adobe Reader remains the current task when is released. Thus it is demonstrated that the correct operation of , like some other aspects of the Windows environment such as the Clipboard chain, depends on individual applications being written correctly.