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/help.c b/src/help.c
index 03cc595..c64538e 100644
--- a/src/help.c
+++ b/src/help.c
@@ -38,7 +38,7 @@
 #include "rb3str.h"
 #include "help.h"
 
-static void teco_help_set(const gchar *topic_name, const gchar *filename, teco_int_t pos);
+static void teco_help_set(const gchar *topic_name, const gchar *filename, gsize pos);
 
 static GStringChunk *teco_help_chunk = NULL;
 
@@ -46,13 +46,14 @@ static GStringChunk *teco_help_chunk = NULL;
 typedef struct {
 	teco_rb3str_head_t head;
 
-	teco_int_t pos;
+	/** position of topic in filename (in bytes) */
+	gsize pos;
 	gchar filename[];
 } teco_help_topic_t;
 
 /** @static @memberof teco_help_topic_t */
 static teco_help_topic_t *
-teco_help_topic_new(const gchar *topic_name, const gchar *filename, teco_int_t pos)
+teco_help_topic_new(const gchar *topic_name, const gchar *filename, gsize pos)
 {
 	/*
 	 * Topics are inserted only once into the RB tree, so we can store
@@ -157,7 +158,7 @@ teco_help_init(GError **error)
 
 		do {
 			gchar *endptr;
-			teco_int_t pos = strtoul(topic, &endptr, 10);
+			gsize pos = strtoul(topic, &endptr, 10);
 
 			/*
 			 * This also breaks at the last line of the
@@ -196,7 +197,7 @@ teco_help_find(const gchar *topic_name)
 }
 
 static void
-teco_help_set(const gchar *topic_name, const gchar *filename, teco_int_t pos)
+teco_help_set(const gchar *topic_name, const gchar *filename, gsize pos)
 {
 	teco_help_topic_t *topic;
 	teco_help_topic_t *existing = teco_help_find(topic_name);
@@ -298,6 +299,8 @@ teco_state_help_done(teco_machine_main_t *ctx, teco_string_t str, GError **error
 	    !teco_ring_edit(topic->filename, error))
 		return NULL;
 
+	teco_current_doc_set_dot(teco_interface_bytes2glyphs_absdot(topic->pos));
+
 	/*
 	 * Make sure the topic is visible.
 	 * We do need undo tokens for this (even though