Cancelling preview yields access violation

rbuser

I'v got a user defined preview screen, with a pppreview component on it.
When the form is closed by the user, i call ppViewer.Cancel in the DoClose
procedure of the form.
SHortly after that the report object is freeAndNil'ed by the destroy method
of the datamodule that own the report.

After this an Access violation is raised in the TppEngine.RequestPage method,
probably because i'v destroyed the report-object too soon.

Is there a report or engine status i have to wait for, before freeing a report
object?

thanks

nardmoseley

Try checking the Report.Printing boolean property. If that is true, then the
report is still busy. Cancel does not immediatedly cancel the report, it
sets a flag that is checked by the report engine and then the report engine
shuts down gracefully.


--
Nard Moseley
Digital Metaphors
www.digital-metaphors.com

rbuser

Hello Nard,

is the engine running in its own thread? and if not ... how can i make it
continue after it has been interupted by the FormCLose event?

nardmoseley

What are you trying to accomplish?

In Windows a modal form executes in a different message loop than the rest
of the program - this makes it seem like it is in a different thread. It is
asynchronous. If an exception occurs it is handled differently. That is true
for all Delphi modal forms.

You can use ReportBuilder to print in a separate thread. See the RBuilder
help topic for Report.BackgroundPrintSettings.

If you Cancel report, it cannot be continued. You can call Report.Reset and
then call Report.Print or PrintToDevices to start generation from the
beginning.

--
Nard Moseley
Digital Metaphors
www.digital-metaphors.com