As veteran OpenInsight programmers know, the system uses a simple boolean flag (exposed as the SAVEWARN property) to determine if the contents of a data-bound form have changed. This flag can be updated in several ways, the most common being:
- From the LOSTFOCUS event of a control.
- From the POSCHANGED, INSERTROW and DELETEROW events of an EDITTABLE control.
- From setting a control’s DEFPROP property.
- From the CLOSE event of a form when the control with focus is inspected to see if it has changed.
It is checked during the CLEAR and CLOSE events to see if it has been set and an “Unsaved Changes” warning issued to the user if so. Most of the time this system works quite well, but (as anyone who has spent several years working with OI systems knows) sometimes it gets triggered when you least expect it, and you’re left with no clue as to why.
To help with this situation the next version of OpenInsight introduces SAVEWARN tracking, so you can see which parts of the system update the SAVEWARN property and when they actually do it. In previous versions the system updated the SAVEWARN flag directly (it’s a simple variable in the “window common area”) but this has been changed to use the Set_Property function so it can be monitored effectively from a single point.
To track SAVEWARN you have two choices:
- Use the SYSMSG event
- Use the System Monitor
Using the SYSMSG event to track SAVEWARN
Every time SAVEWARN is set a standard SYSMSG event is raised with a SAVEWARNINFO code; the system itself does nothing with this message, but it’s there for you to use if you wish. This option is probably more suited for run-time tracing as it’s something you could add to your applications easily if you needed to.
The PS_EQUATES insert record defines the SAVEWARNINFO message number that you can intercept:
equ SYSMSG_SAVEWARNINFO$ to 21 ; // Save warn has been changed - null msg
The Auxiliary parameter passed to the SYSMSG event contains information that describes why the SAVEWARN property was changed.
Using the System Monitor to track SAVEWARN
The SetDebugger() function has been updated to support a new method called “SAVEWARN” that enables SAVEWARN tracking so that changes are displayed in the System Monitor. This option is probably more suited to development use rather than run-time.
From the System Monitor execute:
setdebugger savewarn 1
to turn on tracing, and:
setdebugger savewarn 0
to turn it off.
Setting the SAVEWARN property
If you wish to set SAVEWARN yourself you may use the “index” parameter to pass a description for the change, so this can be picked up in any tracing scenario like so:
Call Set_Property_Only( @Window, "SAVEWARN", TRUE$, "From My Stuff" )
This description is then passed in the Auxiliary parameter of the SYSMSG event as noted above.
Hopefully you will find this facility useful if you ever suffer from problems with SAVEWARN in the future.