Re: [ft-devel] Unable to load OpenType font (test case + font attached)

[suzuki toshiya]

Here is a preliminary patch to permit a font WITHOUT essential tables,
if its header declares CFF/OpenType (by OTTO tag) and CFF table is
included.

This patch does not use cmap table, it uses the character-glyph mapping
info (Encoding dict) in CFF table. It is NOT expected behaviour, because
CID-keyed CFF font for CJK scripts has no Encoding dict. I have to work
more about...

Regards,
mpsuzuki

suzuki toshiya wrote:
> Thank you for providing a sample.
> 
> For first, please let me comment to your question "why". An OpenType
> embedded in PDF should not be expected to be usable as a self standing
> OpenType font. It is a component of PDF, and some essential information
> are removed (because the identical or substitution information are
> stored in the side of PDF). If you check OpenType specification,
>       http://www.microsoft.com/typography/otspec/otff.htm#otttables
> you will find that "head" is essential table and the font lacking it
> is not an officially self-standing OpenType font. And, PDF has their
> own convention how to transform/compress the OpenType font and PDF
> spec does not request the embedded OpenType is conforming to OpenType
> spec.
> 
> # without "head" table, TrueType font parser cannot access the
> # glyph program, because only the "head" table provides the info
> # how to calculate the glyph program storage location from the
> # glyph index. but in this case, "CFF" table is used, so it
> # is not essential.
> 
> Anyway, I understand FreeType is often expected to load the embedded
> OpenType font data in PDF. And, your sample would not require complex
> trick to load as self standing font; Your sample is a simple concatenation
> of cmap table and CFF table. It would not be so difficult changing FreeType
> to pass included CFF stream to CFF parser. But yet I'm not sure if
> the cmap table content should be used (if it should be used, more work
> is needed).
> 
> 
> 
> Regards,
> mpsuzuki
> 
> Harry Roberts wrote:
>> At sfnt/ttload.c:~280
>>
>> The font doesn't have the two expected tables (head, sing) - if I ignore
>> that fact and return `SFNT_Err_Ok` from `check_table_dir` then the font
>> loads fine and renders perfectly.
>>
>> Why does the FreeType TTF loader required these two headers when it works
>> without them?
>>
>> ```
>> 282:     FT_TRACE2(( "check_table_dir:" ));
>> 283: #ifdef TT_CONFIG_OPTION_EMBEDDED_BITMAPS
>> 284:       FT_TRACE2(( " neither `head', `bhed', nor `sing' table found\n"
>> ));
>> 285: #else
>> 286:      FT_TRACE2(( " neither `head' nor `sing' table found\n" ));
>> 287: #endif
>> 288:      error = SFNT_Err_Table_Missing;
>> ```
>>
>> On 7 November 2012 01:12, Harry Roberts <address@hidden> wrote:
>>
>>> Recently I have come across many fonts embedded within PDF files which
>>> cannot be loaded by FreeType v2.4.10.
>>>
>>> I suspect Enfocus PitStop is mangling the fonts when the PDF file is
>>> 'optimized'.
>>>
>>> Attached is the font file (extracted from a PDF) and test case.
>>>
>>> Adobe Acrobat and Photoshop are able to load the fonts. FontForge can also
>>> open the font, and after 'Exporting to OpenType'  the test case is able to
>>> load the font successfully.
>>>
>>> I am still trying to debug the problem, but my knowledge of FreeType and
>>> font format internals is being stretched. Any insight would be appreciated.
>>>
>>> Regards,
>>>  - Harry
>>>
>>
>> ------------------------------------------------------------------------
>>
>> _______________________________________________
>> Freetype-devel mailing list
>> address@hidden
>> https://lists.nongnu.org/mailman/listinfo/freetype-devel
> 
> 
> _______________________________________________
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diff --git a/src/sfnt/ttload.c b/src/sfnt/ttload.c
index 16914f2..22a545b 100644
--- a/src/sfnt/ttload.c
+++ b/src/sfnt/ttload.c
@@ -171,7 +171,7 @@
   {
     FT_Error   error;
     FT_UShort  nn, valid_entries = 0;
-    FT_UInt    has_head = 0, has_sing = 0, has_meta = 0;
+    FT_UInt    has_head = 0, has_sing = 0, has_meta = 0, has_cff = 0;
     FT_ULong   offset = sfnt->offset + 12;
 
     static const FT_Frame_Field  table_dir_entry_fields[] =
@@ -260,6 +260,8 @@
         has_sing = 1;
       else if ( table.Tag == TTAG_META )
         has_meta = 1;
+      else if ( table.Tag == TTAG_CFF )
+        has_cff = 1;
     }
 
     sfnt->num_tables = valid_entries;
@@ -272,7 +274,7 @@
     }
 
     /* if `sing' and `meta' tables are present, there is no `head' table */
-    if ( has_head || ( has_sing && has_meta ) )
+    if ( has_head || ( sfnt->format_tag != TTAG_OTTO && has_cff )  || ( 
has_sing && has_meta ) )
     {
       error = SFNT_Err_Ok;
       goto Exit;
@@ -281,9 +283,9 @@
     {
       FT_TRACE2(( "check_table_dir:" ));
 #ifdef TT_CONFIG_OPTION_EMBEDDED_BITMAPS
-      FT_TRACE2(( " neither `head', `bhed', nor `sing' table found\n" ));
+      FT_TRACE2(( " neither `head', `CFF ', `bhed', nor `sing' table found\n" 
));
 #else
-      FT_TRACE2(( " neither `head' nor `sing' table found\n" ));
+      FT_TRACE2(( " neither `head', `CFF ', nor `sing' table found\n" ));
 #endif
       error = SFNT_Err_Table_Missing;
     }