Re: measureString() oddity

This is not that hard to work around. All you have to do is to obtain
the advances by calling measureString() first, and then to feed those
advances into drawChars(). This will result in the characters being
spaced according to the layout metrics.

Tomas

Roland Kay wrote:
>
>
> Hi Guys,
>
>
>>This is not FT bug, but AW one. The linearHoriAdvance is obtained for
>>layout xft font, but the font which is used to draw is device xft font,
>>which is of different size -- it is scaled by the zoom factor, plus
>>there is 1.5 added to it (see XAP_UnixFont::getDeviceXftFont()). The 1.5
>>is significant at 100%, and I suspect strongly that it is the cause of
>>differences you are seeing. (IIRC it was Martin who added the +1.5,
>>something to do with improved clarity on screen.) You can test if I am
>>correct by removing the 1.5.
>
>
> Setting extra_font_size to 0.0 doesn't solve the problem. I think the 1.5 is
> part of the problem, but it seems more complicated than that. Integer rounding
> seems to be at least partly to blame.
>
> For example, if I change the test to display a "B" where it thinks a string
> of "A"s finishes then I get the following for zoom=86% and extra_font_size=0.0
>
> AAAAAAAAAAAAAAA
> B
>
> But for 87% I get this:
>
> AAAAAAAAAAAAAAA
> B
>
> (Note: In reality, it's actually the A's getting wider not the B moving to the
> left)
>
> What's happening is that at 86% getDeviceXftFont() calculates a font size of
> 12.9pt, which it rounds down to 12pt. At 87% it calculates 13.05pt and rounds
> to 13pt. As a result, the string gets dramatically wider.
>
> In contrast measureUnRemappedChar() is taking the value for a 120pt font from the
> cache and scaling it as a float. Of course, it eventually gets rounded to an
> integer as well, but apparently not in step with the device font.
>
> This looks like being a very fiddly problem!
>
> R.
>
>
>
>
>

                
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Received on Thu Aug 18 08:37:07 2005