[Whookie]

Hi,

in a new project I'm just using TsAlphaImageList and I quite often get an exception in class $C0000005 with message c0000005 ACCESS_VIOLATION as soon as an image should be drawn.

The debugger stops in sGraphUtils.CreateContributors at the following code:

Code:

with Data[Count] do begin
if B < 0 then
Pixel := -B
else
if B >= MaxSize then
Pixel := 2 * MaxSize – B – 1 <-----Exception
else
Pixel := B;

Pixel := Pixel * Delta;
Weight := Round(W * Scale2 * 65536);
end;

This might be due to suspicious code in sGraphUtils.CreateContributors:

1.

Code:

…
CSize := Trunc(AWidth * 2 + 1) * SizeOf(TContributor);
GetMem(Contrib, Size * (SizeOf(TCList) + CSize));

This might or might not allocate enough memory because of the 'AWidth * 2 + 1' term.

2.

Code:

…
Contrib[A].Data := Data;
Data := PContributorList(DWord(Data) + DWord(CSize));
=====

This is definitly a bug and will (or will not) lead to an error depending on where the current memory-block is physically mapped.

I haven't used AlphaControls for quite some time, so I hope you are focused on the project and the 64bit migration (don't know if the code is full of bugs like this, because I just dropped in the image list)!

In general:

Stay away from hard-casts as much as possible, use NativeInt/NativeUInt with pointer arithmentics (or PByte+Inc()).

Stay away from PAnsiChar (for anything except AnsiChars).

Use FastMM4 while testing and define AlwaysAllocateTopDown this will raise errors for most of such bugs.

Also look through message-handling code and make sure you use THandle/LPARAM/WPARAM.

[Support]

Thank you for the message. I will check and I will try to improve it.

If you have a test-application with error and you can share it, this would be great.

[Whookie]

'Support' wrote:

Thank you for the message. I will check and I will try to improve it.

If you have a test-application with error and you can share it, this would be great.

It is a rather big project and I'm on a tight schedule so maybe next month.

To fix my problem do at least the following:

Code:

…
Contrib[A].Data := Data;
Data := PContributorList(NativeUInt(Data) + DWord(CSize));
==========

[Support]

I have changed it to this:

Code:

…
Contrib[A].Data := Data;
Data := PContributorList(PAnsiChar(Data) + CSize);

What you think about the “PAnsiChar” in this case?

[Whookie]

'Support' wrote:

What you think about the “PAnsiChar” in this case?

This will work since you are using a pointer type now.

I think you have some backward compatibility issues to take into account (D2007 and lower?) so it's sort of a good compromise (otherwise I would use

Code:

Data := PContributorList(PByte(Data) + CSize);

instead).

BTW it would be really great to have a selectable background color in the Imagelist window (as I'm working with styles I always have lists with pure white icons and they are invisible)!

[Support]

'Whookie' wrote:

BTW it would be really great to have a selectable background color in the Imagelist window (as I'm working with styles I always have lists with pure white icons and they are invisible)!

I will try to do it in the v12.03

[Whookie]

'Support' wrote:

I will try to do it in the v12.03

Hi, I went to the current version (12.12) and found that you have

* Added support of the BkColor property in the TsAlphaImageList component

in 12.03 but it seems as it isn't what I was after.

So I thought a show you a screenshot of what I'm struggling with:

[attachment=8388:imagelist_win.jpg]

The mouse hovers over image 5 (cursor not shown) so this is the only way to see what image is stored there.

What I meant was something like this:

[attachment=8392:imglst_bk.JPG]

I hacked that into your dialog and attached that project too (you need to remove “.pas” though and unpack it).

[Stephane Senecal]

I think it was a typo. I'm quite sure he meant 12.13 since that's the number of the next version.

Stephane Senecal
CIS Group
Delphi programmer since 2001

[Support]

Hello, Whookie

I think, you need a possibility to change a color of icons background in this dialog. Right?

I can add such ColorSelector there.

[Author]

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