Query.DisableControls - Exception on click
lazarus / 16-Databases

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fpcoder · 2014-02-18 03:40

I wanted the content of a DBGrid to stay visible after closing both
datasets and transactions. That succeded by calling:

Query.DisableControls

And then:

Connection.CloseDataSets;
Connection.CloseTransactions;

DBGrid looks fine while the Transaction and Query is temporarily
deactivated.

Problem: If the grid is clicked or scrolled there is an exception. I
thought that if the control is disabled it shouldn't react to mouse or
keyboard?

If the grid is not clicked or otherwise tampered with, then its no
problem and after Query.EnableControls it runs like before disabling
it.

Is there a fix for this?

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Mike.Cornflake · 2014-02-18 04:36

Query.DisableControls doesn't actually disable the controls.  It
provides a mechanism to allow those controls to know not to respond to
certain database messages.  Definitely a useful call, usually made
before scrolling through a dataset in code.  By setting
.DisableControls, then any grid hooked up for instance knows not to
scroll to the next record when you call Query.Next.

I'm thinking you maybe need to insert a DBGrid.Enabled := False as
well.

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fpcoder · 2014-02-18 05:31

I attempted DBGrid.Enabled := False but get Exception - SIGSEGV when
the calling procedure returns.

Perhaps its not possible to do this with a dataaware control.


Quote from: Mike.Cornflake on February 18, 2014, 05:36:45 amI'm
thinking you maybe need to insert a DBGrid.Enabled := False as well.

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Mike.Cornflake · 2014-02-18 05:59

Can you post your full code?

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exdatis · 2014-02-18 06:14

Also, as prevention, you can handle the event onClick.

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mangakissa · 2014-02-18 08:15

Why not using a memorytable?

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fpcoder · 2014-02-20 04:20

The problem have somehow disappeared and I dont know what caused it.

Made a test app in Delphi7. You can try to click and scroll as much as
you like after Query.Disablecontrols. And it is the same in Lazarus
now.

We'll see if it happens again, then I'll try to pinpoint why.

Thanks for all the answers.

@mangakissa: I'll look into the memdataset, might be useful.