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, 9 insertions, 4 deletions

diff --git a/src/ring.c b/src/ring.c
index 548173b..ceeb730 100644
--- a/src/ring.c
+++ b/src/ring.c
@@ -736,19 +736,24 @@ teco_state_read_file_done(teco_machine_main_t *ctx, teco_string_t str, GError **
 	if (ctx->flags.mode > TECO_MODE_NORMAL)
 		return &teco_state_start;
 
-	sptr_t pos = teco_interface_ssm(SCI_GETCURRENTPOS, 0, 0);
-	teco_undo_int(teco_ranges[0].from) = teco_interface_bytes2glyphs(pos);
+	sptr_t from = teco_interface_ssm(SCI_GETCURRENTPOS, 0, 0);
+	teco_undo_int(teco_ranges[0].from) = teco_current_doc_get_dot();;
 
 	g_autofree gchar *filename = teco_file_expand_path(str.data);
 	/* FIXME: Add wrapper to interface.h? */
 	if (!teco_view_load(teco_interface_current_view, filename, FALSE, error))
 		return NULL;
 
-	pos = teco_interface_ssm(SCI_GETCURRENTPOS, 0, 0);
-	teco_undo_int(teco_ranges[0].to) = teco_interface_bytes2glyphs(pos);
+	/*
+	 * FIXME: Perhaps teco_view_load() should return the number of glyphs added.
+	 */
+	sptr_t to = teco_interface_ssm(SCI_GETCURRENTPOS, 0, 0);
+	teco_undo_int(teco_ranges[0].to) = teco_interface_bytes2glyphs_rel(teco_ranges[0].from,
+	                                                                   from, to-from);
 	teco_undo_guint(teco_ranges_count) = 1;
 
 	if (teco_ranges[0].from != teco_ranges[0].to) {
+		teco_current_doc_set_dot(teco_ranges[0].to);
 		teco_ring_dirtify();
 
 		if (teco_current_doc_must_undo())