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, 26 insertions, 0 deletions

diff --git a/src/ring.h b/src/ring.h
index e45434d..91ce3c9 100644
--- a/src/ring.h
+++ b/src/ring.h
@@ -48,6 +48,12 @@ typedef struct teco_buffer_t {
 	 * This is still a guint, so you can call teco_undo_guint().
 	 */
 	guint state;
+
+	/**
+	 * Dot in glyphs.
+	 * This field is always kept up to date.
+	 */
+	teco_int_t dot;
 } teco_buffer_t;
 
 /** @memberof teco_buffer_t */
@@ -149,3 +155,23 @@ teco_current_doc_must_undo(void)
 	 */
 	return !teco_qreg_current || teco_qreg_current->must_undo;
 }
+
+/** update dot in the current document (Q-Register or buffer) */
+static inline void
+teco_current_doc_set_dot(teco_int_t dot)
+{
+	if (teco_qreg_current) {
+		if (teco_qreg_current->must_undo)
+			teco_undo_int(teco_qreg_current->string.dot);
+		teco_qreg_current->string.dot = dot;
+	} else {
+		teco_undo_int(teco_ring_current->dot) = dot;
+	}
+}
+
+static inline teco_int_t
+teco_current_doc_get_dot(void)
+{
+	return teco_qreg_current ? teco_qreg_current->string.dot
+	                         : teco_ring_current->dot;
+}