OS X provides a mechanism known as Full Keyboard Access to allow keyboard control of all interface elements: checkboxes, radio buttons, popup lists and buttons. Collectively, these items are referred to as Controls. In the Mac OS X built-in help we read:
“… With Full Keyboard Access, you use the Tab key, arrow keys, and space bar to move to and select or activate items on the screen … You can use your keyboard to select … items in windows and dialogs. Selected items are highlighted. You can specify whether you want to use the keyboard to select only text boxes and lists in a window, or all the controls in the window …”
Classic Helix has always allowed a user to control checkboxes and radio buttons from the keyboard — even though the Classic Mac OS never provided such a feature. When a checkbox/radio button has focus in Classic Helix, you can use the arrow keys and the various true/false values (1/0, T/F, Y/N, and any specified custom values) to toggle those controls. Pressing the delete key while a control has focus deletes the value from that control.
These two specifications — Helix’s original spec and the new Mac OS X spec — are similar in some respects, and differ in others. As a result, the ability to tab through controls is not available in OS X Helix at this time.
For OS X Helix to work reliably, you should disable the Full Keyboard Access setting that allows focus for ‘All Controls.’ This prevents Helix from attempting to focus on checkboxes, radio buttons, and popup menus, making tabbing from field to field much more reliable.
It is our intention to address this specification conflict in a future Helix release.
The remainder of this technote discusses the various settings available in Mac OS X, how to determine which is currently active on your computer, and how to set them to avoid Full Keyboard Access related crashes in Helix.
The pictures on the right (click to zoom) show the Keyboard Shortcuts panel in the Keyboard section of System Preferences for OS X 10.4–10.6. You get to this panel by…
- Selecting System Preferences from the Apple menu.
- Clicking on the icon for Keyboard preferences.
- Clicking on the Keyboard Shortcuts tab at the top of the window.
Once you have reached the Keyboard Shortcuts window, look all the way to the bottom of the window, where the main Full Keyboard Access setting is found. Make certain that the Text boxes and lists only radio button is selected.
- OS X 10.6
- On the left side of the window is a list containing various OS X features. In the Keyboard & Text Input section, make sure the Change the way Tab moves focus shortcut is unchecked. This avoids the possibility of accidentally changing this setting.
- OS X 10.4/10.5
- In the scrollable list containing various keyboard shortcuts, locate the section titled Keyboard Navigation (pictured) and uncheck the Move betweeen controls or textboxes and lists shortcut to avoid the possibility of accidentally changing this setting.
Note! The objective here is not to activate/deactivate the shortcut. The real objective is to set Full Keyboard Access to Text boxes and lists only. Simply disabling the shortcut is not enough! You must make sure Full Keyboard Access is set as shown in this image.
After confirming the correct settings, close the System Preferences window.
When the All controls option is selected, you can expect this behavior from Helix:
- 6.1.2: Helix responds to Tab key presses by crashing at unpredictable times.
- 6.1.3 and later: Helix properly focuses on the control, and the OS X behavior is honored. However, when you press Tab to move to the next field, Helix returns the focus to the home field. In other words, it is impossible to tab beyond the first control encountered when the All Controls option is active.
In Helix 6.1.3 and later, a warning dialog (pictured at right) appears when Helix is launched if your Full Keyboard Access settings are such that they will conflict with Helix. This dialog includes a checkbox that allows you to suppress it in the future, but we strongly discourage you from doing that.
You can also test your system’s Full Keyboard Access setting via the Terminal application (in the OS X Utilities folder). Launch Terminal and enter the following line:
defaults read -g AppleKeyboardUIMode
When you press Return, Terminal responds with a value that indicates the current status of Full Keyboard Access.
Val Settings
0 "Full Keyboard Access OFF" and "Text boxes and lists only"
1 "Full Keyboard Access ON" and "Text boxes and lists only"
2 "Full Keyboard Access OFF" and "All controls"
3 "Full Keyboard Access ON" and "All controls"
Helix is most cooperative when the setting is 0 or 1.
We also created a free AppleScript application that shows your current settings. Download it by clicking here.
July 15, 2008: Initial technote, describing the situation in version 6.1.2 (070)
January 6, 2009: Update, describing the situation in version 6.1.3 (092)
September 24, 2010: Updated for OS X 10.6 (Snow Leopard).