Starting from revision 19044, when i put a TVirtualStringTree control in a form the IDE crashes (see attached log). I could not reproduce with other controls and i'm not sure if the problem is in the changes introduced in 19044 or if just revealed a TVirtualStringTree bug.

The VTV code can be obtained from:
https://lazarus-ccr.svn.sourceforge.net/svnroot/lazarus-ccr/components/virtualtreeview-new It requires LCLExtension package:
https://luipack.googlecode.com/svn/trunk/lclextensions

Any help is appreciated.

Luiz
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2009/3/22 Luiz Americo Pereira Camara :

This code was introduced recently by me. This is either my bug or yours, depending on how we decide ;-)

This code does:

      ed := edClass.Create(nil, 1);
      try
        ed.SetPropEntry(0, A.GetComponent(0), propList^[i]);
        ed.Initialize;

note the "nil" hook parameter. So you have to do one of the following:

1) apply the attached patch
(but note that the hook it will pass might be not the right one -- I am not sure)
2) check for nil hook in your Initialize function
3) explain to me how to obtain the correct hook ;-)

If (1) helps, please apply the patch to Lazarus, if you have commit rights.

As a general design note, I think that PropertyEditor.GetAttributes function should be split into "static" and "dynamic" parts, where "static" part supplies type-specific attributes, and "dynamic" -- value-specific ones.

Alexander Klenin wrote

1) apply the attached patch

I somehow managed to save incorrect patch. Please use this version instead.

I applied this patch but it gives the same problem.

FYI, VTV does not define any custom property editor.

How can i know what is the property giving problem? i tried to get the name through calling GetValue in Initialize method of the TListPropertyEditor but returned Unknown.

Luiz

Luiz Americo Pereira Camara wrote

FYI, VTV does not define any custom property editor.

Ok, I was too lazy to download and install VirtualTree and so shot in the dark.

How can i know what is the property giving problem?

Call GetName or GetPropertyPath.

i tried to get the name through calling GetValue in Initialize method of the TListPropertyEditor but returned Unknown.

Hm, I do not see a way TListPropertyEditor.GetValue can return 'Unknown'... Are you sure there is no inherited class?

Now i've got: Columns and TVirtualStringTree.Columns

The problem is that Columns is a property of Header (TVirtualStringTree.Header.Columns).

Previously Columns where streamed as a direct child of TVirtualStringTree using DefineProperties method as a workaround to Delphi bug. I removed this hack and now Columns is streamed as child of Header.
Is there any method, other than DefineProperty, that can change a property hierarchy?

FYI Columns.GetOwner returns the Header instance.

I called both GetValue (0 items) and inherited GetValue (Unknown).

Luiz

On Sun, Mar 22, 2009 at 22:03, Luiz Americo Pereira Camara wrote:

Ok, I have installed VTV (by the way, it needs not only LCLExtensions, but MultiLog package).
I can reproduce the issue, but this time I am inclined to say this is VTV bug, since
similar properties, like StringGrid.Columns and SdfDataSet.FieldDefs work fine. Also, if I disable IsIntresting function, the IDE stops crashing, I can still see anomalies
with Columns property -- for example, TreeView part of object inspector displays garbage after invoking Columns editor for VTV component.

Streaming child properties correctly is, unfortunately, undocumented and clumsy process.
See e.g. r18774 for a sample of changes required (note overrides for TBasicChartSeries class).
If you will use that code, take into account a possible differences in requirement -- TChart
displays its series as child nodes in Object Inspector's treeview. You might or might not want this for VisualTreeView columns.

Columns is a TCollection descendant but is using a TList property editor. The crash probably is due to the cast to TList (TheList:=TList(GetObjectValue);) in TListPropertyEditor.ReadElementCount

Luiz

Luiz Americo Pereira Camara wrote

Luiz Americo Pereira Camara escreveu: Columns is a TCollection descendant but is using a TList property editor. The crash probably is due to the cast to TList (TheList:=TList(GetObjectValue);) in TListPropertyEditor.ReadElementCount

I'm looking at the same piece of code now, but this seems unlikely to me. Columns should use TCollectionPropertyEditor
unless it is specifically overridden by VTV.
Debug printing seems to confirm that.
Anyway, stacktrace points at "Result:=ReadElementCount" like, which is totally insane. Is seems that virtual function table is broken?!

BTW, perhaps it would be easier to use IRC? I'm _Ask_ on #lazarus-ide.

Oh yeah, sorry. When i do a release i'll remove that dependency.

I can reproduce the issue, but this time I am inclined to say this is VTV bug, since similar properties, like StringGrid.Columns and SdfDataSet.FieldDefs work fine.

The difference to that properties is that in VTV case Columns is a subproperty (child of Header).

The problem is that worked fine from 2 years until revision 19044. Anyway i could not find any different approach in VTV since i already removed the existent hack. Can you point any?

I've found where the crash occurs. See other mail.

I'll stick with the basics and hope that the bug can be fixed.

Luiz

I just noticed the TCollectionPropertyEditor is a descendant of TListPropertyEditor. The crash occurs as a sigsegv in TCollectionPropertyEditor.ReadElementCount

at line:

if (Collectionnil) and (Collection is TCollection) then

Somehow GetObjectValue is returning wrong value

Luiz

Alexander Klenin wrote

BTW, perhaps it would be easier to use IRC? I'm _Ask_ on #lazarus-ide.

Yes. Lazarus mailing list has a big lag for me

Luiz

After IRC discussion the fix was submitted to Mantis as http://bugs.freepascal.org/view.php?id=13381