revised and improved the Unicode glyph-to-byte conversion heuristics

Previously almost all glyph-to-byte offset conversions consulted
Scintilla's line index and counted characters on the resulting line.
For instance a simple expression like `.+1J` would scan the same line
twice completely, which would be very slow on pathologically long lines.
Even insertions did that due to having to update the ^Y ranges.
If you repeat such an operation over all characters as in `<.+1:J;>`
you would have complexity O(n^2) for n = line length.
Only commands with an explicit relative nature like `C` and `A` would
use teco_view_glyph2bytes_relative() which scans beginning at dot
as long as the relative movement is less than 1024 glyphs.

Wit the new heuristics almost all glyph-to-byte and byte-to-glyph
conversions can make use of that optimization.
This requires that dot must at all times be known in glyphs as well -
the byte position is managed by Scintilla (SCI_GETCURRENTPOS).
We therefore introduced teco_current_doc_set_dot() and
teco_current_doc_get_dot() to update dot in the current buffer or
Q-Register -- it cannot be stored along with the view since
Q-Registers share a single view.
A number of auxiliary functions have been introduced for
converting relative to a known (glyphs,bytes) offset pair
and for converting absolute and relative positions with regard
to the current doc and SCI_GETCURRENTPOS position.
Of course this is error-prone since the glyph and dot positions
are interdependant - they must always be kept in sync.

With these new optimizations even pathologically long lines can
(usually) be managed even in UTF-8 documents.
It does not address slow-downs in Scintilla's line layout, yet.
grosciteco.tes for instance runs twice as fast now.

1 files changed, 4 insertions, 3 deletions

diff --git a/src/view.h b/src/view.h
index 4c57eb8..86cc3dc 100644
--- a/src/view.h
+++ b/src/view.h
@@ -85,9 +85,10 @@ teco_view_get_codepage(teco_view_t *ctx)
 		? : teco_view_ssm(ctx, SCI_STYLEGETCHARACTERSET, STYLE_DEFAULT, 0);
 }
 
-gssize teco_view_glyphs2bytes(teco_view_t *ctx, teco_int_t pos);
-teco_int_t teco_view_bytes2glyphs(teco_view_t *ctx, gsize pos);
-gssize teco_view_glyphs2bytes_relative(teco_view_t *ctx, gsize pos, teco_int_t n);
+gssize teco_view_glyphs2bytes_rel(teco_view_t *ctx, teco_int_t pos_glyphs,
+                                  gsize pos, teco_int_t n);
+teco_int_t teco_view_bytes2glyphs_rel(teco_view_t *ctx, teco_int_t pos_glyphs,
+                                      gsize pos, gssize n);
 
 teco_int_t teco_view_get_character(teco_view_t *ctx, gsize pos, gsize len);