# User Input

## Mouse Interaction

### Buttons

#### A plethora of pointing devices: mouse, trackball, foot-operated mouse, joystick, trackpad, and a finger-mounted pointing device.

Pictures of different types of pointing device, including mouse, trackball, foot-operated mouse and joystick.

For most users, the mouse provides the main way of interacting with graphical user interfaces. The term "mouse" is used in this chapter to include other pointing devices that can be used to move the pointer around the screen, such as trackballs, trackpads, spaceballs, graphics tablets, or assistive technology devices that emulate a mouse.

For right-handed users, the left button on a conventional mouse is used for the majority of mouse actions. We therefore call it the left button here, even though that may not physically be the case. For this reason, you may sometimes see this button referred to in code or documentation as "Button 1" or the "Selection Button".

Similarly for right-handed users, the right button on a conventional mouse is used for operations involving pop-up menus. We therefore call it the right button in this chapter. You may sometimes see this button referred to in code or documentation as "Button 3" or the "Menu Button".

A conventional mouse with three buttons normally has its third button (or a scrollwheel that acts as a button when pushed) between the left and right buttons. We therefore call it the middle button, but you may sometimes see this referred to in code or documentation as "Button 2" or the "Transfer Button".

#### Guidelines

- Your application uses left button gestures for selecting, activating components, dragging, and the display of drop-down menus.

- Your application uses right button gestures to display and select actions from a popup menu.

- Your application uses the middle button to paste the current PRIMARY (usually the last-highlighted) selection at the pointer position, as follows:

  #### Effect of modifier keys on a middle button transfer operation

  Modifier | Function
  --- | ---
  Unmodified | Copy selection
  Ctrl | Copy selection
  Shift | Move selection
  ShiftCtrl | Create link, shortcut or alias to selection

  Do not over-ride this functionality in any part of your user interface where the transfer action is likely to be useful. If you do intend to use the middle button for a different purpose somewhere, only do so as a shortcut for experienced users, and only for operations that can also be performed without using the right button or middle button.

- If present on the mouse, the scrollwheel should scroll the window or control under the pointer, if it supports scrolling. Initiating scrolling in this way should not move keyboard focus to the window or control being scrolled.

- Ctrl scrollwheel-up should zoom into the window or control under the mouse pointer, and Ctrl scrollwheel-down should zoom out. Zooming in this way should not move keyboard focus to the window or control being zoomed.

- Do not depend on input from the middle or right mouse buttons. As well as being physically more difficult to click, some pointing devices and many assistive technology devices only support or emulate the left mouse button. Some assistive technologies may noteven emulate the mouse at all, but generate keyboard events instead.

- Ensure that every operation in your application that can be done with the mouse can also be done with the keyboard. The only exceptions to this are actions where fine motor control is an essential part of the task. For example, controlling movement in some types of action games, or freehand painting in an image-editing application.

- Do not warp the mouse pointer, or restrict mouse movement to part of the screen. This can interfere with assistive technologies, and is usually confusing even for users who do not rely on assistive technologies.

- Do not require the use of chording (pressing multiple mouse buttons simultaneously) for any operations.

- Do not require the use of multiple (triple- or quadruple-) clicking actions for any operations, unless you also provide an accessible alternative method of performing the same action.

- Allow all mouse operations to be cancelled before their completion. Pressing the Esc key should cancel any mouse operation in progress, such as dragging and dropping a file in a file manager, or drawing a shape in a drawing application.

- Do not assign any actions exclusively to the middle button of a three-button mouse, as not all mice have one.

- Do not hard-code mouse target sizes, or make them too small. Define any mouse targets to be at least as large as the arrow button in a GtkSpinBox in the current gtk theme. Bear in mind that a user with impaired dexterity or vision may be using a theme that results in considerably larger widgets than the default theme.

- Do not refer to particular mouse buttons in your interface unless absolutely necessary. Not everybody will be using a conventional mouse with left, middle and right buttons, so any text or diagrams that refer to those may be confusing.

### Selecting Objects

#### Mouse and keyboard equivalents

For controls or windows that contain a number of objects that the user can select, either singly or multiply, ensure the following mechanisms are in place to allow selections to be made using either the mouse or the keyboard.

##### Standard mouse and keyboard selection mechanisms

| Mouse | Keyboard
--- | --- | ---
Select item, deselect all others | Click | Space
Add/remove item from selection | Ctrl click (toggles item's selected state) | Ctrl Space (toggles focused item's selected state)
Extend selection | Shift click | Shift Space, ShiftHome, ShiftEnd, ShiftPageUp, or ShiftPageDown
Move focus | Click appropriate item to select it | Cursor keys, Home, End, PageUp, and PageDown move focus and selection simultaneously. Ctrl cursor keys, CtrlHome,CtrlEnd, CtrlPageUp, and CtrlPageDown move focus without affecting current selection.
Select All | Click first item, then Shift click last item | CtrlA
Deselect All | Click container background | ShiftCtrlA
Activate selection | Double-click to activate a single selection. Shift or Ctrl double-clicking extends or adds item to selection first before activating the entire selection. | Return activates entire selection. If nothing is currently selected, selects currently-focused item first.
Invert Selection | No mouse equivalent | CtrlI

#### Bounding Box Selection

For a container whose objects may be arranged in two dimensions, for example the icon view in a file manager, allow multiple selection by dragging a bounding box (sometimes called a "rubber band") around one or more objects. Shift left button drag should add all the objects within the bounding box to the existing selection. Ctrl left button drag should toggle the selected state of all the objects within the bounding box.

##### Guidelines

- Allow a bounding box selection to begin only if the initial mouse button press is made:

  - Within the bounds of the container's background, and

  - outside the bounds of any another object in the same container that can be dragged.

  In a drawing application, for example, this means that a bounding box click and drag could start on a blank area of the canvas, or within a shape that had been locked down to prevent accidental editing, but not in an active shape which would itself be dragged instead.

- Select any objects that lie wholly or partly within the bounding box when the mouse button is released.

- Use dynamic highlighting during the drag to show which objects will be selected. Do not wait until the mouse button is released. This avoids any uncertainty about which objects will be selected by the bounding box.

- When a bounding box is being dragged out within a scrollable window, support automatic scrolling of that window when the box is dragged near the window's edges.

##### Examples illustrating dynamic selection highlighting during bounding box selection. In the first example, the folder color and label highlighting changes to indicate selection. In the second, selection is indicated by the addition of resizing handles to selected objects.

Example illustrating dynamic selection highlighting during bounding box selection
Example illustrating dynamic selection highlighting during bounding box selection

### Drag and Drop

Drag and drop is a direct manipulation technique, where you perform actions on selected objects by moving them around the screen with the mouse. You "drag" an object by clicking it, then holding the button while you move the pointer to the object's target location. The object is "dropped" at that location by releasing the mouse button.

#### Guidelines

- Use drag and drop only where the user can reasonably guess what the effect might be. The most common uses are:

  - to move or copy objects from one place to another

  - to link one object to another

  - to perform an action on the objects by dropping them onto an icon representing that action, such as a trash can or printer icon.

- Provide visual feedback throughout a drag and drop operation. Highlight valid targets and change the mouse pointer as it passes over them. Use the "no drop" mouse pointer when passing over invalid drop targets. See also .

- Augment the mouse pointer with a representation of the objects being dragged. Keep this representation small or make it translucent, so as not to obscure possible drop targets underneath it. See also .

  #### Example of copy pointer augmented by an icon representing the file being copied

  Copy pointer superimposed on icon representing a file being copied, to form a "copy file" pointer

- Only allow objects to be copied between applications, not moved. This avoids any confusion about which application's Undo function reverses the operation.

- Allow the user to cancel a drag and drop operation by all of these methods:

  - pressing Esc before releasing the mouse button

  - dropping the object back on its original location

  - performing a query drag and selecting Cancel on the pop-up menu (see )

  - dropping the object on an invalid drop target.

- Allow the user to undo the effects a drag and drop operation by selecting Edit Undo.

- Allow multiple objects to be dragged by Shift or Ctrl selecting them, then dragging any one of the selected objects.

- Ensure that keyboard users can replicate all drag and drop actions using only menu items or keyboard shortcuts, such as Copy (CtrlC) and Paste (CtrlV).

- When an item is being dragged within or into a scrollable window, support automatic scrolling of that window when the mouse is moved near its edges.

- Pop up a menu when the user attemps to drop multiple objects on a target that only accepts single objects. On the menu, list all the objects being dragged, and a Cancel item.

#### Overriding drag and drop behavior

##### Keyboard Modifiers

Allow the user to force the behavior of a drag and drop operation by holding the Ctrl, Shift or both keys throughout. If the user changes modifier keys after they have started the drag, change the mouse pointer immediately and perform the new action when the mouse button is released.

###### Effect of modifier keys during a drag and drop operation

Modifier | Function
--- | ---
Ctrl | Copy
Shift | Move
ShiftCtrl | Create link, shortcut or alias

##### Query Drag

Allow the user to drag objects with the middle button , or with Alt left button. Pop up a menu when the mouse button is released, offering the choice of Copy, Move and Link (or whichever subset of those actions is available), and Cancel. Dragging in this way is known as query drag because it prompts the user before changing anything.

#### Mouse Pointers to Use for Drag and Drop

Use the default GTK drag and drop pointers for the standard transfer operations listed below. This consistency helps ensure the user will know exactly what to expect when they release the mouse button. If you have to design a pointer for a non-standard transfer action not listed here, follow the style of the standard pointers.

##### Mouse Pointers for Drag and Drop

Pointer Shape | Meaning
--- | ---
"Move" pointer | Move selection. The dragged selection will be moved to the drop location, removing it from its previous location.
"Copy" pointer | Copy selection. The dragged selection will be copied to the drop location, leaving the original intact.
"Link" pointer | Link selection. A link to the selection will be inserted at the drop location. How the link appears will be application-dependent, it may be a hyperlink, an icon, or a duplicate of the orignal selection, for example.
"Query drop" pointer | Middle button or Alt-left button drag. A pop-up menu will be posted at the drop location to ask whether the user wants to Move, Copy, or Link the selection, or Cancel the operation.
"Can't drop here" pointer | Can't drop here. Show this pointer while the mouse is over an area where the selection cannot be dropped.

### Mouse Interaction with Panel Applications (Applets)

All objects on the desktop must behave consistently. Despite their specialized nature, applets are no exception.

#### Guidelines

- The unmodified left mouse button must be sufficient to operate all your applet's controls. Applets are meant to be simple enough that modified clicking, or clicking with other mouse buttons (except to pop up the applet's menu) is never required.

- Clicking the right button anywhere within the applet's enclosing window must display either the popup menu for the whole applet, or the popup menu for the control under the mouse pointer. Do not have "dead areas" in your applet that do not respond to a right click.

- Do not use the middle button for anything except dragging the applet to a new location. Middle-clicking and dragging anywhere within the applet window must move the applet, do not require a drag bar or similar device.

  Ctrl left button drag should copy the applet, if moving to another panel; unmodified drag or Shift left button drag should move the applet, if moving to another panel. If moving within same panel, Ctrl=switched movement, Shift=push movement, Alt=free movement.

## Keyboard Interaction

### Keyboard Navigation

A well-designed keyboard user interface plays a key role when you are designing applications. Many power-users prefer to perform most operations with the keyboard rather than the mouse. Visually-impaired users can navigate software more effectively using the keyboard, because using the mouse depends on visual feedback of the mouse pointer location. And mobility impairments can prevent a user from successfully navigating using the mouse, because of the fine motor control skills required.

Make all mouse actions available from the keyboard, and include keyboard access to all toolbars, menus, links and buttons. Every function your application provides must be available using the keyboard alone. Hiding your mouse while you test your application is a great way to test this!

#### Dialog and menu, with some of their access and shortcut keys indicated

Screenshot of a dialog and a menu with some of their access keys and shortcut keys highlighted

Most functionality is easy to make available from the keyboard, by using access keys and shortcut keys, and the toolkit's built-in keyboard navigation features. All controls with labels should have access keys, and frequently-used menu items should be assigned shortcut keys. However, operations that rely on drag-and-drop, for example, may require more thought to make them keyboard accessible.

#### Guidelines

- Provide efficient keyboard access to all application features. In particular, ensure every control on menus and in dialogs are directly focusable using access keys or shortcut keys.

- Use a logical keyboard navigation order. When navigating around a window with the Tab key, keyboard focus should move between controls in a predictable order. In Western locales, this is normally left to right and top to bottom.

- Ensure correct tab order for controls whose enabled state is dependent on check box, radio button or toggle button state. When such a button is selected, all its dependent controls should be enabled, and all the dependent controls of any other button in the group should be disabled. When the user selects a check box, radio button or toggle button that has dependent controls, do not automatically give focus to the first dependent control, but instead leave the focus on the button.

- Do not over-ride existing system-level accessibility features. For example, the MouseKeys feature in the GNOME Keyboard Accessibility preferences dialog allows mouse movement and button clicks to be simulated using the keypad. Therefore you cannot add features to your application that can only be accessed by pressing keys on the keypad, as users relying on the MouseKeys feature will not be able to use them.

- Ensure that any text that can be selected with the mouse can also be selected with the keyboard. This is a convenience for all users, but especially for those for whom fine control of the mouse is difficult.

- Ensure that objects that can be resized or moved by drag and drop can also be resized or moved with the keyboard. For example, icons and windows on the desktop. Where precision sizing and placement is potentially important, e.g. shapes in a diagram, also consider providing a dialog into which you can type co-ordinates, or a means of snapping objects to a user-definable grid.

- Do not use general navigation functions to trigger operations. For example, do not use basic Tab keyboard navigation in a dialog to activate any actions associated with a control.

- Show keyboard-invoked menus, windows and tooltips near the object they relate to, but without hiding or obscuring the object to which the menu or tooltip refers,. In GNOME, popup menus are activated with ShiftF10, and tooltips with CtrlF1.

- Provide more than one method to perform keyboard tasks where possible. Users may find some keys and key combinations easier to use than others.

- Do not assign awkward reaches to frequently performed keyboard operations. Some people may only be able to use one hand on the keyboard, so shortcuts that can be easily used with one hand are preferable for common operations. In any case, having to frequently perform long or difficult reaches on the keyboard can increase muscle strain for all users, increasing the risk of pain or injury.

- Do not require repetitive use of simultaneous keypresses. Some users are only able to press and hold one key at a time. Assistive technologies such as the GNOME Keyboard Accessibility preferences dialog do allow users to press the keys sequentially rather than simultaneously, but this of course means the operation will take longer for them.

### Choosing Access Keys

Give all labelled components an access key (underlined letter), with the exception of toolbar controls which would use up too many access key combinations.

Choose access keys to be as easy to remember as possible. Normally, this means using the first letter of the label. However, in complex windows, the choice can become more difficult. Here are some simple rules:

1. Assign access keys to the most frequently-used controls first. If it's not clear which controls will be the most frequently used, assign access keys from left to right, top to bottom (for Western locales).

2. Use the first letter of the label, or of one of its other words if it has more than one. If another letter provides a better association (e.g. "x" in Extra Large) however, consider using that letter instead.

3. If the first letter is not available, choose an easy to remember consonant from the label, for example, "p" in Replace.

4. If no such consonants are available, choose any available vowel from the label.

If duplication of access keys in a window is unavoidable, you should still refrain from duplicating the access keys for any of these buttons that appear in the same window: OK, Cancel, Close, Apply or Help.

Also, it is better not to assign access keys to "thin" letters (such as lowercase i or l), or letters with descenders (such as lowercase g or y) unless it is unavoidable. The underline does not show up very well on those characters in some fonts.

Applications using a non-Roman writing system in conjunction with a standard keyboard can have control labels prefixed with Roman characters as access keys.

### Choosing Shortcut Keys

The tables in summarize the standard shortcut keys to use when your application supports those functions. Your application will not necessarily support all of these functions, see for more information. However, use the recommended shortcut keys for those functions you do support.

You will probably want to add your own shortcut keys for functions specific to your application. If so, as well as following the guidelines below, look at any other existing similar applications to see which shortcut keys they have defined. Your users may already be using those or similar applications, so being consistent where it is possible and sensible to do so will provide a better user experience for them when they begin to use yours.

#### Guidelines

- Use Ctrl letter in preference to other combinations when choosing new shortcut keys.

- Insert, Delete, Home, End, Page Up and Page Down are acceptable shortcut keys for functions that are closely related to those keys' normal system-defined uses. Do not assign them to unrelated functions just because you've run out of other shortcut key combinations, however.

- Only assign shortcut keys to the most commonly-used actions in your application. Do not try to assign a shortcut key to everything.

- Choose new shortcut keys to be as mnemonic as possible, as these will be easier to learn and remember. For example, CtrlE would be a good shortcut for a menu item called Edit Page.

- Use ShiftCtrlletter for functions that reverse or extend another function. For example, CtrlZ and ShiftCtrlZ for Undo and Redo.

  #### Unicode entry shortcuts

  Note that you cannot use ShiftCtrlA-thru-F or ShiftCtrl0-thru-9 for your own purposes, as these combinations are used to enter unicode characters in text fields.

- Do not use Ctrlnumber or numbered function keys as shortcut keys, unless the number has some obvious relevance to the action. For example, Ctrl2 and Ctrl3 may be acceptable shortcut keys for View 2D View and View 3D View in a 3D modelling application.

- Do not use Altkey combinations for shortcut keys, as these may conflict with window manager or menu access keys.

- Do not use symbols that require Shift or other modifiers as part of a shortcut, for example Ctrl%. Remember that symbols that can be accessed without a modifier key on your keyboard may be more difficult to access on different international keyboards.

- Do not assign shortcut keys to menu items that change over time, for example a list of open windows on the Window menu, or a recently-used file list on the File menu. Do assign access keys to these items, however.

- Do not use any of the standard shortcut keys listed in for your own purposes, even if your application doesn't support those functions. This helps reinforce consistency between all GNOME applications.

### Standard Application Shortcut Keys

If your application uses any of the standard functions listed in the following tables, use the recommended standard keyboard shortcut for that function.

#### Standard GNOME application shortcut keys and access keys - File menu

Function | Shortcut | Description
--- | --- | ---
New | CtrlN | Create a new document
Open | CtrlO | Open a document
Save | CtrlS | Save the current document
Print | CtrlP | Print the current document
Close | CtrlW | Close the current document
Quit | CtrlQ | Quit the application

#### Standard GNOME application shortcut keys and access keys - Edit menu

Function | Shortcut | Description
--- | --- | ---
Undo | CtrlZ | Undo the last operation
Redo | ShiftCtrlZ | Redo the last operation
Cut | CtrlX | Cut the selected area and store it in the clipboard
Copy | CtrlC | Copy the selected area into the clipboard
Paste | CtrlV | Paste contents of clipboard at mouse/cursor position
Duplicate | CtrlU | Duplicate the currently-selected items and add them to the same window, without affecting the clipboard
Select All | CtrlA | Select everything in focused control or window
Invert Selection | CtrlI | Select everything in focused control or window that was previously unselected, and deselect everything that was previously selected
Delete | Del | Delete selection
Find... | CtrlF | Find matches in the current document, highlighting them in-place
Search... | CtrlF (see note below) | Search for matches in multiple documents, files or other external sources
Find Next | CtrlG | Find the next match
Replace... | CtrlH | Find and replace matches
Rename | F2 | Switch the selected item's label into edit mode, allowing user to type in a new name.

#### Find and Search

If your application requires both Edit Find and Edit Search menu items, use ShiftCtrlF as the shortcut for Search.

#### Standard GNOME application shortcut keys and access keys - View menu

Function | Shortcut | Description
--- | --- | ---
Zoom In | Ctrl Plus | Zoom in on the document
Zoom Out | Ctrl Minus | Zoom out of the document
Normal Size | Ctrl 0 | Restore to zoom level to normal size (generally 100%)
Refresh | CtrlR | Redraw current view of document, without checking if content has changed
Reload | CtrlR (see note below) | Reload the current document, updating content from source if necessary
Properties | AltEnter | Display the selected object's Properties window. May alternatively appear on the File menu if the document itself is the only object in the application whose properties can be inspected.

#### Reload and Refresh

If your application requires both View Reload and View Refresh menu items, use ShiftCtrlR as the shortcut for Reload.

#### Standard GNOME application shortcut keys and access keys - Bookmarks menu

Function | Shortcut | Description
--- | --- | ---
Add Bookmark | CtrlD | Add a bookmark for the current location
Edit Bookmarks... | CtrlB (see note below) | Open a window in which the user can edit and organise saved bookmarks

#### Bold and Edit Bookmarks

If your application requires both Format Bold and Bookmarks Edit Bookmarks... menu items, use ShiftCtrlD as the shortcut for Edit Bookmarks.

#### Standard GNOME application shortcut keys and access keys - Go menu

Function | Shortcut | Description
--- | --- | ---
Back | Alt Left | Go to the previous location in the navigation chain
Next | Alt Right | Go to the next location in the navigation chain
Up | Alt Up | Go up one level in the navigation hierarchy
Home | Alt Home | Go to the starting page defined by the user or application
Location... | Ctrl L | Present or focus an entry field into which the user can type a new address or location to view

#### Standard GNOME application shortcut keys and access keys - Format menu

Function | Shortcut | Description
--- | --- | ---
Bold | CtrlB | Make selected text bold/regular
Underline | CtrlU | Underline/remove underline from selected text
Italic | CtrlI | Make selected text italic/regular

#### Standard GNOME application shortcut keys and access keys - Help menu

Function | Shortcut | Description
--- | --- | ---
Contents | F1 | Show help contents page for the current application

#### Standard Window Manager Shortcut Keys

The following shortcut keys are used by many window managers, and should not normally be over-ridden by your application.

##### Standard window manager shortcut keys and access keys

Function | Shortcut | Description
--- | --- | ---
Switch primary windows | AltTab, ShiftAltTab | Switch focus to the next or previous top level window on the desktop
Switch panels | CtrlAltTab, ShiftCtrlAltTab | Switch focus to the next or previous panel on the desktop
Log out | CtrlAltDel | Open the session logout confirmation dialog
Window menu | AltSpace | Open the window menu
Close | AltF4 | Close the focused window
Restore | AltF5 | Restore the focused to its previous size
Switch secondary windows | AltF6, ShiftAltF6 | Switch focus to the next or previous secondary window associated with the application ( )
Move | AltF7 | Move the focused window
Resize | AltF8 | Resize the focused window
Minimize | AltF9 | Minimze the focused window
Maximize | AltF10 | Maximize the focused window
Full Screen | CtrlF11 | Show the window in full screen mode, with no border, menubar, toolbar or statusbar

#### Standard Widget Navigation Shortcut Keys

The following shortcut keys are reserved for keyboard navigation use by the various widgets used in GNOME, and should not normally be over-ridden by your application.

##### Standard GNOME keyboard navigation keys for widgets

Key | Function
--- | ---
Tab, ShiftTab | Moves keyboard focus to next/previous control
CtrlTab, ShiftCtrlTab | Moves keyboard focus out of enclosing widget to next/previous control, in those situations where Tab alone has another function (e.g. GtkTextView)
CtrlF1 | Pop up tooltip for currently-focused control
ShiftF1 | Show context-sensitive help for currently-focused window or control
F6, ShiftF6 | Give focus to next/previous pane in a GtkPaned window
F8 | Give focus to splitter bar in paned window
F10 | Give focus to window's menu bar
ShiftF10 | Pop up contextual menu for currently-selected objects
Space | Toggle selected state of focused check box, radio button, or toggle button
Return | Activate focused button, menu item etc.
Home, End | Select/move to first item in selected widget
PageUp, CtrlPageUp, PageDown, CtrlPageDown | Scroll selected view by one page up/left/down/right

#### Additional Widget Navigation Shortcut Keys

The following emacs-style navigation shortcut keys are still available in GNOME 2.0 text entry fields (by selecting the "emacs" scheme in the GNOME Keyboard Shortcuts preferences dialog), but are disabled by default. Since some users will still want to use them, do not over-ride them for your own purposes in any situations where a text entry control has focus.

##### Emacs-style navigation keys for widgets

Key | Function
--- | ---
CtrlA | Move cursor to beginning of line
CtrlD | Delete character following/under cursor
CtrlE | Move cursor to end of line
CtrlK | Delete from cursor to end of line
CtrlU | Delete current line
CtrlW | Cut to clipboard
CtrlY | Paste from clipboard
Ctrl Space | Set mark
CtrlDel, AltD | Delete from cursor to end of word
Ctrl Backspace | Delete from cursor to start of word
Alt Space | Delete all whitespace around cursor, reinsert single space
Alt\ | Delete all whitespace around cursor

### Keyboard Interaction with Panel Applications (Applets)

Panels have been fully keyboard navigable since GNOME 2.0. Since your panel application can gain keyboard focus, you must ensure that it is also keyboard navigable.

The rules for panel application keyboard navigation are mostly the same as those for any other window. However, there is one imporant difference:

- Do not use the the Tab key as the means of moving focus between controls in a panel application. Use the arrow keys for this purpose instead.

When an object on a panel has focus, the Tab key normally moves focus to the next object on the panel. If your panel application also used Tab for its own internal navigation, the user would have to press CtrlTab to move focus out of your panel application instead. This inconsistency would be detremental to the user experience.