[HarfBuzz] Can I only reshape broken clusters?

[kelvinsthirteen at gmail.com]

> On Jun 30, 2016, at 11:41 PM, Behdad Esfahbod <behdad at behdad.org> wrote:
> 
> No, it wouldn't be safe necessarily.  That's exactly what the
> unsafe-to-break API is about, but that's not finished yet.  For now,
> you have to reshape the entire new string.

That’s O(n^2) in terms of the amount of shaping that has to be done per paragraph based on the length of the paragraph text, and not workable in practice

> 
>> On Thu, Jun 30, 2016 at 8:31 PM, Kelvin Ma <kelvinsthirteen at gmail.com> wrote:
>> If I have the string A = 'affifibcd' and the master list of shaped glyphs
>> 
>> [a 0] [ffi 1] [fi 4] [b 6] [c 7] [d 8]
>> 
>> and I wanted to shape the substring A[2:] ('fifibcd'), could I simply take
>> my preshaped glyphs after the cluster at or above (ceiling) i = 2 and only
>> reshape the segment A[2:6]?
>> 
>> So I would reuse the glyphs
>> 
>> [fi 4] [b 6] [c 7] [d 8]
>> 
>> and reshape the segment A[2:6] = 'fifi' to get
>> 
>> [fi 2] [fi 4]
>> 
>> and add them together (dropping the last glyph in the reshaped segment) to
>> get
>> 
>> [fi 2]  [fi 4] [b 6] [c 7] [d 8]
>> 
>> ?
>> Would this be the same result as reshaping the entire segment A[2:]? Would
>> this still work for RTL text, or a substring that’s on the left-hand side of
>> the parent string like A[:5] = 'affif'?
>> 
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> 
> 
> 
> -- 
> behdad
> http://behdad.org/