[OpenJDK 2D-Dev] Strange text rendering with SRC + Extra Alpha

[Phil Race]

I didn't get time to look at this yesterday.
I think the problem is (sort of) in SunGraphics2D.setComposite() where 
we have

                }
            } else if (newCompType == CompositeType.SrcNoEa ||
                       newCompType == CompositeType.Src ||
                       newCompType == CompositeType.Clear)
            {

This then categorises the composite state "SRC" as COMP_ISCOPY
regardless of whether there is an extra alpha.

This code was introduced in  
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6248957

I believe that there's some handling of the extra alpha for most 
rendering but
its enough to mislead SurfaceData into thinking it can create and use 
LCD glyphs.
I've not yet looked into what exactly happens after that but it
seems like we end up  in a loop that uses the LCD glyph
data as if its greyscale mask and you'll get garbage.

If this is the case we can't rely on the compositeState variable and
will need to check the composite type.

-phil.

Denis Lila wrote:
> Hello.
>
> After noticing some weird things I made some modifications to
> Clemens' test. I've attached the results and the tester.
> The most interesting results are the first 18 lines in each
> image, all of which are produced by rendering to INT_RBG type
> buffered images. The first 6 lines have both AA_ON and subpixel aa.
> Lines 7-12 have only subpixel AA, and lines 13-18 have only AA_ON.
> In each group of 6, the only thing that changes is the order in
> which the hints, the composite, and the colour are set.
>
> Lines 1-6 and 13-18 don't look right on closed jdk (1.6.0_21-b06).
> The only thing they have in common is that the AA hint is on.
> Lines 7-12 look ok - they only have LCD AA. We can see that the order
> doesn't matter.
>
> On openJDK7 (with a build of a fresh clone of the 2d tree) lines
> 1-3 look like what Clemens is seeing, but the next 3 don't look bad,
> even though all of the first 6 lines are supposed to be drawn with
> a black colour, SRC compositing, and both AA_ON and LCD AA.
> The same goes for lines 13-15. What lines 1-3 and 13-15 have in
> common is that the colour is set after the composite.
> Lines 7-12 still look ok, but they are a bit different from what closed
> java produces, even though subpixel antialiasing is clearly used in both.
>
> That's it for my observations.
> Regards,
> Denis.
>
> ----- "Clemens Eisserer" <linuxhippy at gmail.com> wrote:
>
>   
>> Hi again,
>>
>> Attached is the sample program as well as the output I get on
>> jdk7b99,
>> when running the sample program attached.
>>
>> - Clemens
>>     
>>
>> ------------------------------------------------------------------------
>>
>>
>> ------------------------------------------------------------------------
>>