gdi32 : Questions about SetDIBColorTable and GetDIBColorTable

[Laurent Vromman]

Hi,

I am looking deeper inside gdi32 in order to continue helping wine after my first try on WidenPath.

Something looks strange to me in SetDIBColorTable and GetDIBColorTable.

GetDIBColorTable is structured like this : 

if (dc->funcs->pGetDIBColorTable)
    result = dc->funcs->pGetDIBColorTable;
else
{
    result = local implementation;
}
return result;

This looks normal. If dc->funcs->pGetDIBColorTable is available, wine uses it, else it uses a local implementation.
In both cases, the return value is the result of the chosen operation.

But I have more difficulties with SetDIBColorTable :

result = local implementation;

if (dc->funcs->pGetDIBColorTable)
    dc->funcs->pGetDIBColorTable;

return result;

Whatever happen next, the local implementation is used. Then if pGetDIBColorTable is available, it is used too. I see here a second call for the same thing, even if the local implementation succeed. Moreover, the result of dc->funcs->pGetDIBColorTable is not used as a return value.
Is there a mistake here, or is there something I do not understand ?

GetDIBColorTable uses the local implementation only if dc->funcs is not available. That is not the case for SetDIBColorTable, which runs first the local implementation.
What is the right policy to apply here ? 

I believe the call order of pSetDIBColorTable and the fact its return value is not used are errors. Am i wrong? If someone can confirm I am not, I will provide a patch in the next days.

Thank you for your help and time,

Laurent Vromman

[Alexandre Julliard]

Laurent Vromman <laurent(a)vromman.org> writes:
> Whatever happen next, the local implementation is used. Then if
> pGetDIBColorTable is available, it is used too. I see here a second
> call for the same thing, even if the local implementation
> succeed. Moreover, the result of dc->funcs->pGetDIBColorTable is not
> used as a return value.  Is there a mistake here, or is there
> something I do not understand ?
>
> GetDIBColorTable uses the local implementation only if dc->funcs is
> not available. That is not the case for SetDIBColorTable, which runs
> first the local implementation.  What is the right policy to apply
> here ?

Both are correct. gdi32 always stores the color table, so it has to be
updated upon SetDIBColorTable no matter what the driver does; while
GetDIBColorTable doesn't need to access it if the driver has a better
way of doing it. This way the driver can either:

1. not implement anything, get and set are handled by gdi32;
2. let gdi32 maintain the local copy but still do something when the
   color table is changed;
3. implemented both set and get to override gdi32 completely.

-- 
Alexandre Julliard
julliard(a)winehq.org