Question

In GUI dialogs, most applications provide for keyboard control as follows:

1. Enter key – presses the default button. (Default is usually indicated with a bold button border.)
2. Esc key – presses the Cancel or close button.
3. Space key – presses widget that currently has keyboard focus.
4. Tab key – advances focus to next widget.

Question is, when keyboard focus is on a widget that is a button, should the default button be changed to be the one with focus?

I see some issues with this behavior:

1. The display noise of redrawing buttons to unbold the outline of original default button and rebold the button under focus as being new default.
2. The Space key is now somewhat redundant with Enter key.
3. There is no keyboard accelerator to get the normal default button now (Usually the OK button).

However, it seems the trend has been in this direction to change the default button with focus change to another button. What is the rationale for this departure from the early GUIs? It would seem to provide less functionality given there is no way to press the original default button. Did people find that the original model was too complicated for users to understand? I would think keyboard control of dialogs would be a task for advanced users who would have no trouble understanding the model and prefer to have accelerator for current button (Space) and original default button (Enter) at all times.

Note that Qt for one is supporting the change: QPushButton’s autoDefault property is responsible for the behavior of changing the default button. By default its value is true. Therefore, you must take extra action to set it to false for all buttons, to prevent them from becoming the default button when focused.

Answer 1

This is not a "departure from the early GUIs", at least not if by "early GUIs", you mean Windows 1.0. The behavior that you describe has been this way since the beginning.

The focused button is always "pushed" when the Enter key is pressed. The default button is only triggered in the following two situations:

• The default button has the focus (which it does by default), or
• The focus is on a control that does not process Enter key presses (such as a static control, or a single-line textbox that does not have the ES_WANTRETURN style flag set).

The famous Win32 blogger Raymond Chen has a post explaining this behavior (focus specifically on the last two quoted paragraphs):

A dialog box maintains the concept of a "default button" (which is always a pushbutton). The default button is typically drawn with a distinctive look (a heavy outline or a different color) and indicates what action the dialog box will take when you hit Enter. Note that this is not the same as the control that has the focus.

For example, open the Run dialog from the Start menu. Observe that the OK button is the default button; it has a different look from the other buttons. But focus is on the edit control. Your typing goes to the edit control, until you hit Enter; the Enter activates the default button, which is OK.

As you tab through the dialog, observe what happens to the default button. When the dialog box moves focus to a pushbutton, that pushbutton becomes the new default button. But when the dialog box moves focus to something that isn’t a pushbutton at all, the OK button resumes its position as the default button.

The dialog manager remebers which control was the default button when the dialog was initially created, and when it moves focus to something that isn’t a button, it restores that original button as the default button.