[reportlab-users] Incorrect character composition

[Robin Becker]

On 21/04/2015 11:50, Glenn Linderman wrote:
> On 4/21/2015 2:51 AM, Robin Becker wrote:
>> Glenn,
>>
>> my reading of the control sequence(s) is that these glyphs are being
>> individually positioned in PDF; I see 12 separate Tm operators.
>
> I agree.
>
>> I ideally we should see a single BT with a string containing 14 bytes which
>> would imply that acrobat handles all the glyph positioning.
>
> I think we are on the same wavelength here, but I think you meant to say "Adobe
> Reader (or other PDF display tool)" where you said "Acrobat".  I think it is the
> case that "Acrobat", (or other PDF generation tool), is doing all the
> positioning, and encoding it into the PDF file.

yes the positioning is not being done by the renderer (acrobat reader/evince etc 
etc).

If that is the case then positioning has to be done by the software that 
produces the PDF ie illustrator/acrobat reader pro/reportlab. If this is true 
then there's no point in including the GPOS information into the embedded fonts.

If reportlab has to do the positioning of glyphs it should not affect the 
existing standard mechanisms. Probably we'll need a cumbersome, slow and fairly 
complicated text output mechanism.
>
> The below seems to be referring to the Nuance generated file, the Acrobat file
> used HEX codes.
>
> "Ideally", of course, refers to the way it should work if the PDF viewer's
> renderer was responsible for combined glyph positioning. Of course, if it was,
> it should also be responsible for rendering the kerning too, and then you
> wouldn't be able to do right justification very well... it would have to be
> predicted in one place and matched in the other... so I think the PDF technique
> is to have the viewer only convert curves to pixels, following instructions by
> the PDF creator as to where those curves should be placed, actually produces
> more consistent results across platforms and devices... as much as it hurts to
> have to do the calculations for the Td or Tm parameters when generating the PDF.
.........

well I think kerning is a separate issue. Here we are talking about a standard 
unicode approach to composite glyph construction. Pairs/groups of glyphs are 
supposed to be treated in a specific way; kerning is optional.

-- 
Robin Becker