The line edit control displays a single line of text to the user and allow the user to enter unconstrained text. If more than one line is required a text edit is the right control. Because line edits are unconstrained and don't accept valid data only, input validation and problem handling should be handled carefully.
Is this the right control?
- Use edits for input of single lines of unconstrained text.
- In case of multiple lines of text or more than a few words, use a text edit
- Don't use a line edit if only a specific type of data is valid. Use a control for constrained input.
- Mask letters if edit is used to enter passwords.
- When setting a new password, have it entered twice to prevent typos in passwords.
- Provide a "Show password" checkbox to unmask the password both when setting new and when entering existing passwords.
- Consider to use auto-complete feature to help users when entering data that is likely to be used repeatedly.
- If the user enters a character that is known to be invalid, ignore the character and display an input problem hint that explains the valid characters (e.g. numbers vs. characters).
- If the input data has a value or format that is known to be invalid, display an input problem hint when the text box loses input focus (e.g. wrong zip code format).
- If the input data is inconsistent with other controls on the window, give an error message when the entire input is complete, such as when users click OK for a modal dialog box.
- Don't clear invalid input data unless users are not able to correct errors easily. Doing so allows users to correct mistakes without starting over.
- When disabling the line edit, also disable any associated labels and buttons.
- Label every line edit with a descriptive caption to the left (cf. Alignment).
- Create a buddy relation so access keys are assigned.