(compute_motion): Doc fixes.

1 files changed, 9 insertions, 4 deletions

diff --git a/src/indent.c b/src/indent.c
index 5eef49c3a16..83122d3b0db 100644
--- a/src/indent.c
+++ b/src/indent.c
@@ -401,6 +401,11 @@ struct position val_compute_motion;
    and vpos give its cartesian location.  I'm not clear on what the
    other members are.
 
+   Note that FROMHPOS and TOHPOS should be expressed in real screen
+   columns, taking HSCROLL and the truncation glyph at the left margin
+   into account.  That is, beginning-of-line moves you to the hpos
+   -HSCROLL + (HSCROLL > 0).
+
    For example, to find the buffer position of column COL of line LINE
    of a certain window, pass the window's starting location as FROM
    and the window's upper-left coordinates as FROMVPOS and FROMHPOS.
@@ -422,12 +427,12 @@ struct position val_compute_motion;
             FRAME_HAS_VERTICAL_SCROLL_BARS (XFRAME (WINDOW_FRAME (window)))
           and frame_width = FRAME_WIDTH (XFRAME (window->frame))
 
-        Or,
-          window_internal_width (w) - 1
+   Or you can let window_internal_width do this all for you, and write:
+        window_internal_width (w) - 1
 
    The `-1' accounts for the continuation-line backslashes; the rest
    accounts for window borders if the window is split horizontally, and
-   the scroll bars if the frame supports them.  */
+   the scroll bars if they are turned on.  */
 
 struct position *
 compute_motion (from, fromvpos, fromhpos, to, tovpos, tohpos, width, hscroll, tab_offset)
@@ -537,7 +542,7 @@ compute_motion (from, fromvpos, fromhpos, to, tovpos, tohpos, width, hscroll, ta
               vpos++;
               hpos = 0;
               hpos -= hscroll;
-              if (hscroll > 0) hpos++; /* Count the $ on column 0 */
+              if (hscroll > 0) hpos++; /* Truncation glyph on column 0 */
               tab_offset = 0;
             }
         }