On Before Keystroke
| Code | Can be called by | Definition |
|---|---|---|
| 17 | 4D Write Pro area - Combo Box - Form - Input - List Box - List Box Column | A character is about to be entered in the object that has the focus. Get edited text returns the object's text without this character. |
History
| Release | Changes |
|---|---|
| 18 R5 | - Support in non-enterable list boxes - The event is now triggered after IME validation |
Description
After the On Before Keystroke and On After Keystroke event events are selected for an object, you can detect and handle the keystrokes within the object, using the Form event code command that will return On Before Keystroke and then On After Keystroke event (for more information, please refer to the description of the Get edited text command). Within the On Before Keystroke event, the FILTER KEYSTROKE command can be used to filter typed chars.
These events are also activated by language commands that simulate a user action like
POST KEY.
The On Before Keystroke event is not generated:
- in a list box column method except when a cell is being edited (however it is generated in any cases in the list box method),
- when user modifications are not carried out using the keyboard (paste, drag-and-drop, checkbox, drop down list, combo box). To process these events, you must use
On After Edit.
Non-enterable objects
The On Before Keystroke event can be generated in non-enterable objects, e.g. in a list box even if the list box cells are not enterable, or rows are not selectable. This allows you to build interfaces where the user can scroll dynamically to a specific row in a list box by entering the first letters of a value. In case where the list box cells are enterable, you can use the Is editing text command to know if the user is actually entering text in a cell or is using the type-ahead feature and then, execute appropriate code.
Keystroke sequence
When an entry requires a sequence of keystrokes, the On Before Keystroke and On After Keystroke events are generated only when the entry is fully validaded by the user. The Keystroke command returns the validated character. This case mainly occurs:
- when using "dead" keys such as ^ or ~: events are generated only when the extended character is eventuelly entered (e.g. "ê" or ñ),
- when an IME (Input Code Editor) displays an intermediary dialog box where the user can enter a combination of characters: events are generated only when the IME dialog is validated.