“Alt-Tab”的意思、由来-开放百科全书

{{key press|Alt|Tab}} is the common name for a keyboard shortcut that has been in Microsoft Windows since Windows 3.0. This shortcut switches between application-level windows without using the mouse; hence it was named Task Switcher (Flip in Windows Vista).

Perhaps the most common use of {{key press|Alt|Tab}} is to alternate between a full-size window and the desktop, but it can also be used to switch to any running program that has an application-level window. Thus, it can be used alternate between the two most recent tasks. 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 {{key press|Alt|Tab}} keyboard combination has also been incorporated in other operating systems and desktop environments such as macOS and iOS (as {{key press|Cmd|Tab}}), KDE, Xfce, and GNOME.

Behavior

The use of the modifier key {{key press|Alt}} in using {{key press|Alt|Tab}} differs from typical modifier key use in the following ways:

There are many subtleties to the behavior of {{key press|Alt|Tab}}, and they have remained mostly unchanged over the years.

The task list does not change order while it is open, but the order of tasks can change between invocations of the task list.

Windows Vista changed the default behavior^{[{{key press|Tab}}-{{key press|Tab}}... 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 {{key press|Alt|Tab}} but the application fails to update its place in the z-order (for example, if its window procedure is hung), then the next time {{key press|Alt|Tab}} 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 {{key press|Alt|Tab}} 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^[2]

The order of the {{key press|Alt|Tab}} 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.^[3]

Windows-specific issues and hacks

Under Windows XP, the Tweak UI PowerToy,^[6] can adjust the number of rows and columns in the task list window, or it can be adjusted via a registry edit.^[7] This is helpful if there are so many windows that the list would spill over into multiple pages.

Another Microsoft PowerToy, {{key press|Alt|Tab}} Replacement,^[6] is available for Windows XP that displays a screenshot of each application in the task list rather than just its icon, and allows the user to use the mouse to select the desired application. A more advanced version of this functionality, named Windows Flip, is built into Windows Vista.

A number of third-party tools, similar to {{key press|Alt|Tab}} Replacement, are also available that add additional functionality to {{key press|Alt|Tab}}.

Additionally, Windows Vista and Windows 7 allow the user to navigate through the {{key press|Alt|Tab}} menu using mouse or arrow keys.

When the Aero Glass theme is enabled, Windows Vista also offers a 3D view of the windows themselves that animates as the user cycles through it. The behaviour is very similar to {{key press|Alt|Tab}} and is accessed by holding down the {{key press|Win}} key instead of {{key press|Alt}} while pressing {{key press|Tab}}. While this view is visible, windows can be selected and made active by clicking on them with the mouse, and the list can be scrolled forward or backward using the mouse scroll wheel.

If there is only one window on the system, Windows does not show a selector dialog at all when {{key press|Alt|Tab}} is pressed; the key sequence will simply restore or give focus to that window in case it is minimized or not focused. This means that under Windows 10, {{key press|Alt|Tab}} no longer functions as a way to switch out of a full-screen application, since the desktop is no longer a window.

If the user prefers the smaller XP icons over the larger Vista "thumbnail" icons, they can change the functionality by:

In Windows 7 {{key press|Alt|Tab}}, after a one-second delay, displays the full-sized application window immediately each time the cursor position changes, hiding all other windows. This is a part of Aero Peek feature, new in Windows 7. This behavior can be disabled along with Aero Peek: Control Panel - Performance Information and Tools - Adjust visual effects - uncheck Enable Aero Peek.

Delay is adjustable by setting the LivePreview_ms value in HKEY_CURRENT_USER\\Software\\Microsoft\\Windows\\CurrentVersion\\Explorer\\AltTab registry key.

Some users report that the switcher dialog does not stay on top^[8]^[9] while it is displayed, but one can navigate through this dialog using mouse even if it is completely overlapped by some window. This bug is reported to be user profile specific. Some user profiles on the same machine may encounter this bug, some not. As discovered, the problem is sometimes caused by desktop gadgets system. After killing sidebar.exe process (which hosts the gadgets), the problem disappears. After restarting sidebar the problem appears again. This bug also happens when ipoint.exe, the Microsoft Intellipoint mouse driver, is running. Other programs causing this behaviour were reported as well.^[10]

The actual reason this problem occurs is because [zero-sized always-on-top windows at (0,0)] cause Windows Explorer to set the alt-tab properties incorrectly. The solution is to download and run a program which will remove these flags.^[11] download

A poorly thought-out and immature prank in an earlier revision of this page suggested that the problem originated with the keyboard drivers, and rebooting and unplugging was the only way to fix it. Not only was the answer incorrect and misleading, but it may not even fix the problem if the alt-tab bug is triggered by an autostarting program.

To show the XP icons in Windows 7 advanced users can add a new DWORD value AltTabSettings in the registry key

Using Windows 7 the additional key combination {{key press|Ctrl|Alt|Tab}} brings up the switcher dialog and it remains on screen after all the keys have been released. A user can move through the dialog in any direction using the arrow keys, or {{key press|Tab}} through in a linear manner, wrapping at the end of the list back to the beginning. In this mode, the {{key press|Enter}} key or a mouse click selects the desired window which gains the focus and the dialog is dismissed; {{key press|Esc}} dismisses with no change of focus.

In Windows 7, to use a switcher dialog similar to that in XP, one can keep Left-{{key press|Alt}} pressed, tap on Right-{{key press|Alt}} and then press {{key press|Tab}}.

There is a common^[12]^[13] problem associated with the use of {{key press|Alt|Tab}}. It is very easy for the user to mistakenly use {{key press|Alt|Shift}} instead, changing the system language through the use of a default keybind. To solve this issue, go into Control Panel/Regional Settings/Languages/Details and there is a button that allows the user to configure the shortcuts to switch languages - he/she can disable it or change it to something harder to press by mistake. This problem is reported on Windows XP and Windows 7.

There is a bug in Windows 7, that sometimes {{key press|Alt|Tab}} does not work. Various solutions exist, search the web.{{Citation needed|date=May 2015}}

Non-Windows functionality

Macintosh

Similar functionality exists on macOS using {{key press|Command}} instead of {{key press|Alt}}, and switching between applications rather than windows. The Macintosh 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 {{key press|H}} or {{key press|Q}} keys without closing the menu. {{key press|Command|`}} works similarly to switch between windows within the same application. Once {{keypress|Command|Tab}} has been invoked, {{key press|Command|`}} changes behavior to mimic {{key press|Command|Shift|Tab}} (i.e. it cycles backwards). The {{key press|left}} and {{key press|right}} arrow keys may also be used to navigate the application switcher.

This functionality does not switch to a window that has been minimized. To restore such a window, one needs to press {{key press|Command|Tab}} as many times as necessary to choose the desired window, and press the Option key just prior to releasing the Command button. This will restore the minimized window.{{Citation needed|reason=What? Command tab is only about application switching, nothing to do with individual windows! User:CyberSkull 07:11, 6 June 2011 (UTC)|date=June 2011}}

There was no default key binding for application switching in the classic Mac OS. Third party control panels (such as ApplWindows and LiteSwitch) provided this behavior.

iOS

iOS adds comparable functionality using {{key press|Command}} instead of {{key press|Alt}}, 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. {{key press|Command|Shift|Tab}} cycles backwards, as in OS X.

Unix

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 press|Alt|Tab}} 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 {{key press|Alt|Tab}} 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

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.

GNOME

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.

History

The {{key press|Alt|Tab}} 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".^[14]

Before CoolSwitch, the {{key press|Alt|Tab}} combination was similar to the {{key press|Alt|Esc}} combination (which also switched windows), but {{key press|Alt|Esc}} redrew each window immediately on each stroke, while {{key press|Alt|Tab}} brought the windows to the top but did not redraw them until the Alt key was released.

Inconsistency

An example of a program that violates the expectation that pressing {{key press|Alt|Tab}} 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 {{key press|Alt|Tab}} 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 {{key press|Alt|Tab}}: first an icon representing the main Reader window and then an icon for the individual document. While in Adobe Reader, pressing {{key press|Alt|Tab}} one time selects the second item in the list, which is the icon for the PDF document. Adobe Reader remains the current task when {{key press|Alt|Tab}} is released. Thus it is demonstrated that the correct operation of {{key press|Alt|Tab}}, like some other aspects of the Windows environment such as the Clipboard chain, depends on individual applications being written correctly.

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