This format takes one character variable and displays it in a single line edit box so that the user can change it. Optionally, it can be modified with an integer n that sets the width of the box in characters. The edit box will then scroll horizontally when necessary. For multiple line edit boxes see %re (%re (Multiline Edit Box)) and %eb (Edit box (%eb)).
str='Initial string padded with spaces if needed'
It is important to note that because there is an obvious difference between the widths of characters e.g. 'i' and 'W', the width is specified in 'average characters'.
A grave accent format modifier (`) is used to make the control read-only. In this form no surrounding box is displayed, and the string can only be changed by the program, using WINDOW_UPDATE@ to reflect the changes. This should be used in place of %ws (Display String) when it is necessary to display a string which needs to be updated. A similar effect is produced with %st (String). (see Variable string). The caret is added to provide a call-back function that will be called on every change to the edit window.