WindowManager Errors (changes)
Showing changes from revision #4 to #5:
Added | Removed | Changed
» Part 7 - The Desktop?
» WindowManagerThe Window Manager
» Technical Details
» Errors
Overview
Errors can be very difficult to detect and fix and may cause both the user and developer great frustration if left unfixed.
If an application unfortunately fails to deal with an error, it should, as a bare minimum report the error to the user in a friendly manner, explaining what has happened.
Common Errors
| # | Common Error |
|---|---|
| 1 | Always check for errors when calling a Wimp SWI. |
| 2 | The redraw loops can be a source of infinite error loops. If a redraw fails, then the Wimp will again ask for the area to be redrawn, which cause the same error as before and so on. |
| 3 | Missing Fonts can cause to infinite looping if error checking is not implemented. |
| 4 | Wimp_CreateWindow and Wimp_CreateIcon should always be error proof, to ensure that no data are lost if the calls fail. |
| 5 | Check cases concerning running out of space. |
Error Messages
The table below provides a quick overview of some of the most common error messages that your application may have to deal with.
| Error Code | Error Message |
|---|---|
| &280 | Wimp unable to claim work area. The RMA area is full. |
| &281 | Invalid Wimp operation in this context. Some operations are only allowed after a call to Wimp_Initialise. |
| &284 | Window definition won’t fit. No room in RMA for window. |
| &286 | Wimp_GetRectangle called incorrectly. |
| &287 | Input focus window not found. |
| &288 | Illegal window handle. |
| &289 | Bad work area extent. Visible window is set to display a non-existent part of the work area. |
| &29F | Bad parameter passed to Wimp in R1. |
Social
Follow us on
and
and
ROOL Store
Buy RISC OS Open merchandise here, including SD cards for Raspberry Pi and more.