Text Entry Fields
Text entry fields are used for entering one or more lines of plain text. In GTK 2, the GtkEntry control is used for single-line text entry, and GtkTextView for multiple-line text entry.
-
Label the entry field with a text label above it or to its left, using sentence capitalization. Provide an access key in the label that allows the user to give focus directly to the entry field.
-
Right-justify the contents of entry fields that are used only for numeric entry, unless the convention in the user's locale demands otherwise. This is useful in windows where the user might want to compare two numerical values in the same column of controls. In this case, ensure the right edges of the relevant controls are also aligned.
-
When the user gives focus to an entry field using the keyboard, place the text cursor at the end of the existing text and highlight its contents (but don't overwrite the existing PRIMARY clipboard selection). This makes it easy to immediately overtype or append new text, the two most common operations performed on entry fields.
-
Size text entry fields according to the likely size of the input. This gives a useful visual cue to the amount of input expected, and breaks up the dialog making it easier to scan. Don't make all the fields in the dialog the same width just to make everything line up nicely.
-
In an instant-apply property or preference window, validate the contents of the entry field when it loses focus or when the window is closed, not after each keypress. Exception: if the field accepts only a fixed number of characters, such as a hexadecimal color code, validate and apply the change as soon as that number of characters have been entered.
-
Provide a static text prompt for text boxes that require input in a particular format or in a particular unit of measurement. For example:
Figure 6-4 Text entry field with static text prompt
-
Where possible, provide an additional or alternative control that limits the required input to the valid range. For example, provide a spinbox or slider if the required input is one of a fixed range of integers, or provide access to a GtkCalendar control if the user has to enter a valid date:
Figure 6-5 Text entry field requiring a date as input, with a button beside it to pop up a GtkCalendar control to simplify the task
This is less error-prone than expecting the user to format their text input in some arbitrary format. You may still want to provide the entry field control as well, however, for expert users who are familiar with the required format.
-
If you implement an entry field that accepts only keystrokes valid in the task context, such as digits, play the system warning beep when the user tries to type an invalid character. If the user types three invalid characters in a row, display an alert that explains the valid inputs for that textfield.
-
The cursor blink rate is globally defined by the XSettings "gtk-cursor-blink" and "gtk-cursor-blink-time". Standard toolkit controls use these and they must not be altered in applications by any means. New controls with text cursors must respect these global values.
- 6.4.1. Behavior of Return key
- 6.4.2. Behavior of Tab key
6.4.1. Behavior of Return key
Normally, pressing Return in a dialog should activate the dialog's default button, unless the focused control uses Return for its own purposes. You should therefore set the activates-default property of most entry fields to TRUE. (Note that GtkTextView does not have such a setting— pressing Return always inserts a new line.).
However, if your dialog contains several entry fields that are usually filled out in order, for example Name, Address and Telephone Number, consider setting the activates-default property on those entry fields to FALSE. Pressing Return should then move focus on to the next control instead. Doing this will help prevent the user from accidentally closing the window before they have entered all the information they wanted to.
As a further safeguard, remember not to set the default button in a dialog until the minimum amount of required information has been entered, for example, both a username and a password in a login dialog. Again, in this case you should move focus to the next control when the user presses Return, rather than just ignoring the keypress.
If you need to provide a keyboard shortcut that activates the default button while a GtkTextView control has focus, use Ctrl+Return.
Gtk does not currently move focus to the next control when Return is pressed and either activates-default=FALSE, or there is no default button in the window. For now, Return does nothing in these situations, so remember to implement the focus change behavior yourself.
6.4.2. Behavior of Tab key
Normally, pressing Tab in a single-line entry field should move focus to the next control, and in a multi-line entry field it should insert a tab character. Pressing Ctrl+Tab in a multi-line entry field should move focus to the next control.
If you need to provide a keyboard shortcut that inserts a tab character into a single line entry field, use Ctrl+Tab. You are unlikely to find many situations where this is useful, however.