Questions about the font shaping tender

Chris Sherlock chris.sherlock79 at
Tue Feb 2 10:41:41 CET 2016

Would it be helpful to look at the way that OutputDevice handles laying out text?

When I was looking at this code early last year I found that I had to try to understand what OutputDevice did before I could come even *close* to understanding what SalLayout was attempting. 

For instance, the DX array code looks suspiciously like it was adopted from the way that EMF (and I guess Windows GDI?) handles text layout. 

If I were to start a Wiki page, would that be at all helpful? It would be rough, but if others wanted to correct my mistakes and misunderstandings then could this be helpful in any way?


> On 2 Feb 2016, at 8:15 PM, Miklos Vajna <vmiklos at> wrote:
> Hi,
> I think the problem to solve is that we have different layout on Linux,
> Windows and OS X, which means it's next to impossible to write unit
> tests that assert the text is laid out correctly, since there can be
> small differences today. The hope is that this is the root cause of e.g.
> the chart tests which are not enabled by default today.
> As far as I know, there are two ways you can solve this:
> - use the Linux stack everywhere (fontconfig, freetype, harfbuzz?
>  something like that), IIRC that's what e.g. Chromium does
> - create a 4th layout in VCL, which is just a stub, but gives exactly
>  the same results in all platforms, to allow writing unit tests that
>  are executed in all platforms
> Regards,
> Miklos
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