[liblouis-liblouisxml] Re: Bert Frees: Use of Buffers
- From: Bert Frees <bertfrees@xxxxxxxxx>
- To: liblouis-liblouisxml@xxxxxxxxxxxxx
- Date: Thu, 19 Jan 2012 14:52:53 +0100
Hi John,
outbuf1 is the buffer that was already there (used to be just outbuf I
think). I've added 2 additional buffers that come after the first.
Unlike the first, the 2nd and 3th can be bypassed. They are only
needed in some special cases, which I will explain below:
Special case 1: The setting printPageNumberRange is set to yes, and
the setting printPageNumberAt is set to top.
This means that the whole range of print pages contained in a Braille
page is displayed at the top of the page. This is used a lot in
Belgium. For example, if a braille page contains the last part of
print page 10 and the first part of print page 11, the first line of
the braille page will say: 10-11.
Because in this case, the first line of the page can not be created
until the rest of the page is finished, lines 2 till N are first
written to outbuf2. Then, the first line is written, bypassing
outbuf2. Then, outbuf2 is read out. All this is done in the function
nextBraillePage.
Special case 2: For some element, one or more of the style attributes
dontSplit, keepWithNext or orphanControl are set to yes.
Processing such elements sometimes requires multiple iterations. For
example, let's say dontSplit is set to yes. Before writing the
element, the whole 'state' of the program (including outbuf1 and
outbuf2) is stored. Then, outbuf3 is enabled and the first iteration
is done. If the element fits on the Braille page, outbuf3 is read out
and we can move on. If the element doesn't fit on the Braille page,
the previous state is restored, outbuf3 is discarded and we do a
second iteration. This time, we start the element on a new Braille
page so that it will fit on this page. All this is done in
transcribe_paragraph.c
I still like the idea of cascading multiple buffers, but I'm not sure
if my implementation is very good, performance-wise. You may have to
look at that.
Best,
Bert
On 18-jan-12, at 19:33, John J. Boyer wrote:
Hi Bert,
I am putting your changes into the utd functions in liblouisutdml.
Could
you explain the use of the three buffers, outbuf1 outbuf2 outbuf3
Incidentally, I have moved the buffers off the stack and into
user_data.
This makes them available for the string translation functions as well
for file translation functions. They also come in handy for utd and
for
converting utd to other formats.
Thanks,
John
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