[OpenJDK 2D-Dev] RFR: 8132890 Text overlapping on dot matrix printers.

[Sergey Bylokhov]

Hi, Phil.
Looks like in this method we have too many things named as deviceXX. Am 
I understand correctly that
1) AffineTransform deviceTransform = getTransform(); returns 
device+users transformation?
2) fontTransform contains full transform dev+user+font?
And in the fix we remove trueDeviceTransform from the fontTransform, to 
calculate advance? I wonder how many steps we do for that.

One small cleanup is possible also, the deviceTransform is not used 
anymore after the fix in textOut();

On 17.10.15 2:16, Phil Race wrote:
> https://bugs.openjdk.java.net/browse/JDK-8132890
> http://cr.openjdk.java.net/~prr/8132890/
>
> The notable thing about this case is that the printer has different dpi
> in x and y.
>
> In GDI printing we detect when the transform under which the font is
> rendered is non-uniform as in that case we want to tell GDI to create
> a stretched font as that is better than trying to draw the text as a
> filled path.
> What happens here is that the *device resolution* is not uniform.
>
> It is a scale of (3.33, 2.0) - ie 240x144 dpi so x=1.66*y
>
> This device resolution then gets combined with any graphics transform
> and the font transform and we have lost sight of the fact that the
> non-uniform part came from the device rather than the application
> specifying an additional x-scale factor to be applied.
> GDI is already accounting for the real device resolution and we cause
> it to be applied twice.
>
> So we need to divide this out as part of the calculation.
> This needs access to the real device dpi to be passed in/made available.
>
> But there is another issue.  JDK puts the printer job into portrait mode
> even in landscape printing and takes care of the transforms itself.
> So the size used to set the font for GDI needs to use GDI's idea of the
> orientation.
>
> I augmented a text printing test used to verify this with some
> additional scenarios.
> It is now a pretty comprehensive test of many different scenarios.
> It has been tested on an HP LaserJet, the Oki dot matrix printer and the
> XPS driver.
>
> There is also a not completely necessary tweak here to adjust the error we
> allow in gdi vs jdk advances from 0.2% to 1%. This made for about a 25%
> reduction in the overall spool file size for my test with no noticeable
> consequences.
>
> -phil.
>


-- 
Best regards, Sergey.