Re: font substitution

[Fred Kiefer]

Thank you for the patches. I already applied the first one. For the
other two I would like to understand the problem they try to solve a bit
better, before working around it.

The illegal value for the character set are really strange. The value
GNUstep checks  against is 1114112, which should be the maximal allowed
UNICODE value. I could understand, if GNUstep would be off by one. Could
you please test this or send me such a font, then I would have a look
myself.

The matrix swapping is also strange. In many case your work around would
be fine, but in others when the matrix was explicitly set it would be
wrong. Here it would be nice to know which case are handled correct and
which wrong by the current code. Is there anything special in the way
you created you font?

Cheers,
Fred

Yen-Ju Chen wrote:
> O.K. Sorry for another reply
> This patch fixes the upside-down problem.
> The attached screenshot uses English font as default font
> and Chinese font as substitute.
> I probably need to find a Japanese font and a symbol font to test
> multiple substitute.
> By the way, the speed is not bad.
> Previously I said that it takes 1-2 seconds for 25,000+ Chinese glyphs
> is including putting all glyphs on a NSMatrix.
> So it is fast to get the coverage in NSFont.
> 
> Yen-Ju
> 
> On 8/10/07, Yen-Ju Chen <yjchenx@gmail.com> wrote:
>> Another issue is that sometimes freetype fails to get the coverage.
>> Therefore, NSCharacterSet raise an exception:
>> "Specified range exceeds character set".
>> So this patch prevents NSAttributedString from using all available fonts
>> to eliminate the possibility of using bad fonts.
>> It only uses user specified fonts for substitution.
>> And I hope GNUstep can add an user default to specify the preferred fonts.
>>
>> Once the patch is applied, the font substitute basically works, but
>> has one problem.
>> I attach a screenshot to explain that.
>> The left window is using English font as default font and no preferred font.
>> So you only see English 'GNUstep'.
>> The middle window is using Chinese font as default font and no preferred 
>> font.
>> Because Chinese font also contains English letter,
>> you see both English and Chinese.
>> You can tell the English letter is from different font.
>> The right window is using English font as default font and Chinese
>> font as substitute.
>> Again, you can see both English and Chinese character.
>> But the funny thing is the Chinese character is upside-down.
>> I have no idea why it happens, but I suspect gui or back cache the font 
>> matrix
>> so the matrix of English font is applied to the Chinese font.
>> The hint of Chinese font is also different between middle and right window.
>> The middle one is sharp while the right one is blur.
>> It indicates something is cached, probably for the English font at the
>> start of the text.
>> Maybe someone has insights about what may cause it.
>>
>> Yen-Ju
>>
>> On 8/10/07, Yen-Ju Chen <yjchenx@gmail.com> wrote:
>>> Hi,
>>>
>>>   [NSFont coveredCharacterSet] is broken.
>>>   I attach a patch.
>>>   A quick test shows that a Chinese font which contains 25,000+ glyph
>>>   takes only about 1-2 seconds to go through.
>>>   It's on a powerbook G4 1GHz.
>>>   So cache may not be needed for coveredCharacterSet.
>>>   I haven't test the preferredFont yet.
>>>   Hope this patch can go in soon.
>>>
>>>   Yen-Ju
>>>
>>> On 8/9/07, Yen-Ju Chen <yjchenx@gmail.com> wrote:
>>>> On 8/9/07, Fred Kiefer <fredkiefer@gmx.de> wrote:
>>>>> Yen-Ju Chen wrote:
>>>>>> On 8/8/07, Fred Kiefer <fredkiefer@gmx.de> wrote:
>>>>>>> Yen-Ju Chen wrote:
>>>>>>>>   Another thing I am thinking is to save the coveredCharacterSet on 
>>>>>>>> disk.
>>>>>>>>   Font does not change frequently,
>>>>>>>>   and it does take time to generate coveredCharacterSet for each font,
>>>>>>>>   especially for CJK.
>>>>>>>>   If the cached coveredCharacterSet can be saved on disk and loaded 
>>>>>>>> later,
>>>>>>>>   it can reduce the overhead of starting an application.
>>>>>>>>   For art backend, it can even pack the saved coveredCharacterSet in 
>>>>>>>> nfont.
>>>>>>>>   So for small font, it is fine to check the covered character each 
>>>>>>>> time.
>>>>>>>>   For big font, saved character set is better.
>>>>>>>>
>>>>>>> Great idea! Would you like to work on that?
>>>>>>   If the patch you have goes into the -trunk,
>>>>>>   I can play with it and see how much it effects the speed
>>>>>>   and decide what's the best way to do the cache if needed.
>>>>>>
>>>>> I just committed this change, now it is your turn :-)
>>>>   Thanx. I will take a look shortly.
>>>>
>>>>   Yen-Ju
>>>>
>>>
>>
>>
>> ------------------------------------------------------------------------
>>
>> Index: NSAttributedString.m
>> ===================================================================
>> --- NSAttributedString.m     (revision 25384)
>> +++ NSAttributedString.m     (working copy)
>> @@ -990,7 +990,7 @@
>>  - (NSFont*)_substituteFontWithName: (NSString*)fontName font: 
>> (NSFont*)baseFont
>>  {
>>    // FIXME: Catch case were baseFont is nil
>> -  return [NSFont fontWithName: fontName matrix: [baseFont matrix]];
>> +  return [NSFont fontWithName: fontName size: [baseFont pointSize]];
>>  }
>>  
>>  - (NSFont*)_substituteFontFor: (unichar)uchar font: (NSFont*)baseFont 
>> fromList: (NSArray *)fonts
>> @@ -1061,13 +1061,6 @@
>>      {
>>        return subFont;
>>      }
>> -
>> -  subFont = [self _substituteFontFor: uchar font: baseFont fromList: 
>> -                      [[NSFontManager sharedFontManager] availableFonts]];
>> -  if (subFont != nil)
>> -    {
>> -      return subFont;
>> -    }
>>    
>>    return nil;
>>  }
>>
>> ------------------------------------------------------------------------
>>