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, 8 insertions, 5 deletions

diff --git a/src/doc.c b/src/doc.c
index 9bc9dc8..40217f4 100644
--- a/src/doc.c
+++ b/src/doc.c
@@ -77,7 +77,7 @@ teco_doc_edit(teco_doc_t *ctx, guint default_cp)
 	              (sptr_t)teco_doc_get_scintilla(ctx));
 	teco_view_ssm(teco_qreg_view, SCI_SETFIRSTVISIBLELINE, ctx->first_line, 0);
 	teco_view_ssm(teco_qreg_view, SCI_SETXOFFSET, ctx->xoffset, 0);
-	teco_view_ssm(teco_qreg_view, SCI_SETSEL, ctx->anchor, (sptr_t)ctx->dot);
+	teco_view_ssm(teco_qreg_view, SCI_SETSEL, ctx->anchor, (sptr_t)ctx->pos);
 
 	/*
 	 * NOTE: Thanks to a custom Scintilla patch, representations
@@ -124,7 +124,7 @@ teco_doc_undo_edit(teco_doc_t *ctx)
 	 */
 	//undo__teco_view_set_representations(teco_qreg_view);
 
-	undo__teco_view_ssm(teco_qreg_view, SCI_SETSEL, ctx->anchor, (sptr_t)ctx->dot);
+	undo__teco_view_ssm(teco_qreg_view, SCI_SETSEL, ctx->anchor, (sptr_t)ctx->pos);
 	undo__teco_view_ssm(teco_qreg_view, SCI_SETXOFFSET, ctx->xoffset, 0);
 	undo__teco_view_ssm(teco_qreg_view, SCI_SETFIRSTVISIBLELINE, ctx->first_line, 0);
 	undo__teco_view_ssm(teco_qreg_view, SCI_SETDOCPOINTER, 0,
@@ -222,9 +222,11 @@ void
 teco_doc_update_from_view(teco_doc_t *ctx, teco_view_t *from)
 {
 	ctx->anchor = teco_view_ssm(from, SCI_GETANCHOR, 0, 0);
-	ctx->dot = teco_view_ssm(from, SCI_GETCURRENTPOS, 0, 0);
+	ctx->pos = teco_view_ssm(from, SCI_GETCURRENTPOS, 0, 0);
 	ctx->first_line = teco_view_ssm(from, SCI_GETFIRSTVISIBLELINE, 0, 0);
 	ctx->xoffset = teco_view_ssm(from, SCI_GETXOFFSET, 0, 0);
+
+	ctx->dot = teco_view_bytes2glyphs_rel(from, 0, 0, ctx->pos);
 }
 
 /** @memberof teco_doc_t */
@@ -232,9 +234,11 @@ void
 teco_doc_update_from_doc(teco_doc_t *ctx, const teco_doc_t *from)
 {
 	ctx->anchor = from->anchor;
-	ctx->dot = from->dot;
+	ctx->pos = from->pos;
 	ctx->first_line = from->first_line;
 	ctx->xoffset = from->xoffset;
+
+	ctx->dot = from->dot;
 }
 
 /**
@@ -252,7 +256,6 @@ teco_doc_exchange(teco_doc_t *ctx, teco_doc_t *other)
 	memcpy(other, &temp, sizeof(*other));
 }
 
-/** @memberof teco_doc_t */
 void
 teco_doc_clear(teco_doc_t *ctx)
 {