text-motion: add functions to get/set position based on display width

This is inherently a tricky thing to do because we cannot rely on
the current display state. The reason being that the position/cursor
which is modified might not currently be in the visible area.

Tabs are a particular problem because they have a variable display
width. However this new code is certainly not worse than the current
behaviour which relies on text_line_char_{get,set} and thus simply
counts graphemes.

Not yet completely convinced that this is the right approach.

1 files changed, 4 insertions, 0 deletions

diff --git a/text-motions.h b/text-motions.h
index cf108b3..dfe3acc 100644
--- a/text-motions.h
+++ b/text-motions.h
@@ -43,6 +43,10 @@ size_t text_line_offset(Text*, size_t pos, size_t off);
 int text_line_char_get(Text*, size_t pos);
 /* get position of the `count' grapheme in the line containing `pos' */
 size_t text_line_char_set(Text*, size_t pos, int count);
+/* get display width of line upto `pos' */
+int text_line_width_get(Text*, size_t pos);
+/* get position of character being displayed at `width' in line containing `pos' */
+size_t text_line_width_set(Text*, size_t pos, int width);
 /* move to the next/previous grapheme on the same line */
 size_t text_line_char_next(Text*, size_t pos);
 size_t text_line_char_prev(Text*, size_t pos);