[fpc-devel] Patch, font rendering on Arm-Linux devices.

[Bernd Mueller]

Daniël Mantione wrote:
> 
> 
> Op Tue, 26 Feb 2008, schreef Bernd Mueller:
> 
>> Daniël Mantione wrote:
>>>
>>>
>>> Op Tue, 26 Feb 2008, schreef Florian Klaempfl:
>>>
>>>> Daniël Mantione schrieb:
>>>>>
>>>>>
>>>>> Op Tue, 26 Feb 2008, schreef Vincent Snijders:
>>>>>
>>>>>> Bernd Mueller schreef:
>>>>>>> Hello,
>>>>>>>
>>>>>>> the attached patch avoids misaligned data access (bus errors), 
>>>>>>> during
>>>>>>> font rendering (with the graph unit) on Arm-Linux devices.
>>>>>>>
>>>>>>
>>>>>> Instead of testing for arm cpu, you could use
>>>>>> FPC_REQUIRES_PROPER_ALIGNMENT too. So it is fixed for sparc as well.
>>>>>
>>>>> Well, packed records are usually used when speed is unimportant. If 
>>>>> the
>>>>
>>>> Isn't this used to read a font file?
>>>
>>> You are right. Therefore, the "unaligned" pseudo function is the 
>>> proper solution.
>>
>> the main affected routines are unpack and decode. Both routines were 
>> called for every single character (only for a stroked font) via 
>> OutTextXYDefault. So speed is not unimportant ;-)
> 
> Loosing a few clock cycles per character is completely acceptable, and 
> even the right engineering decision regarding size/memory trade-off. It 
> would be different if it would be a few clock cycles per pixel. Anyway, 
> the BGI font file format cannot be changed, so in such case the internal 
> data structures would need to be different from the ones on disk. Not 
> worth the effort.

The affected TStroke-Record has nothing to do with the BGI font file 
format. I would not consider this a patch BTW, if you have to change the 
CHR font file format to make it work.

I usually make my engineering decisions on facts and benchmarks. The 
(very unexpected) result of this benchmark is, that a version with 
leaving the TStroke-Record packed, is about 13 % faster than the 
original patch. I am going to send a new patch soon.

Regards, Bernd.