Fix and document components of mouse event position.

 src/keyboard.c (make_lispy_position): Put a meaningful value in yret
 when the click is on the header or mode line.
 doc/lispref/commands.texi (Click Events): Document the values of X, Y and
 COL, ROW in the event's position, when the click is on the header or
 mode line, on the fringes, or in the margins.

4 files changed, 28 insertions, 7 deletions

diff --git a/doc/lispref/ChangeLog b/doc/lispref/ChangeLog
index 8f57bc45da5..d1c2d861eb7 100644
--- a/doc/lispref/ChangeLog
+++ b/doc/lispref/ChangeLog
@@ -1,3 +1,9 @@
+2010-11-26  Eli Zaretskii  <eliz@gnu.org>
+
+        * commands.texi (Click Events): Document the values of X, Y and
+        COL, ROW in the event's position, when the click is on the header
+        or mode line, on the fringes, or in the margins.
+
 2010-11-17  Eli Zaretskii  <eliz@gnu.org>
 
         * customize.texi (Composite Types): Lower-case index entry.
diff --git a/doc/lispref/commands.texi b/doc/lispref/commands.texi
index 17cfcc0def8..d83396750ca 100644
--- a/doc/lispref/commands.texi
+++ b/doc/lispref/commands.texi
@@ -1285,8 +1285,12 @@ input stream.  @xref{Key Sequence Input}.
 @item @var{x}, @var{y}
 These are the pixel coordinates of the click, relative to
 the top left corner of @var{window}, which is @code{(0 . 0)}.
-For the mode or header line, @var{y} does not have meaningful data.
-For the vertical line, @var{x} does not have meaningful data.
+For a click on text, these are relative to the top left corner of
+the window's text area.  For the mode or header line, they are
+relative to the top left window edge.  For fringes, margins, and the
+vertical border, @var{x} does not have meaningful data.  For fringes
+and margins, @var{y} is relative to the bottom edge of the header
+line.
 
 @item @var{timestamp}
 This is the time at which the event occurred, in milliseconds.
@@ -1316,7 +1320,12 @@ the window.
 @item @var{col}, @var{row}
 These are the actual coordinates of the glyph under the @var{x},
 @var{y} position, possibly padded with default character width
-glyphs if @var{x} is beyond the last glyph on the line.
+glyphs if @var{x} is beyond the last glyph on the line.  For clicks on
+the header or mode line, these are measured from the top left edge of
+the header or mode line.  For clicks on the fringes and on the
+vertical border, these have no meaningful data.  For clicks on the
+margins, @var{col} is measured from the left edge of the margin area
+and @var{row} is measured from the top of the margin area.
 
 @item @var{image}
 This is the image object on which the click occurred.  It is either
@@ -1333,7 +1342,7 @@ left corner of the character glyph clicked on.
 These are the pixel width and height of @var{object} or, if this is
 @code{nil}, those of the character glyph clicked on.
 @end table
- 
+
 @sp 1
 For mouse clicks on a scroll-bar, @var{position} has this form:
 
diff --git a/src/ChangeLog b/src/ChangeLog
index 61ef9a202a8..eac550a7334 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2010-11-26  Eli Zaretskii  <eliz@gnu.org>
+
+        * keyboard.c (make_lispy_position): Put a meaningful value in yret
+        when the click is on the header or mode line.
+
 2010-11-25  Eli Zaretskii  <eliz@gnu.org>
 
         * xdisp.c (set_cursor_from_row): Don't forget to consider the
diff --git a/src/keyboard.c b/src/keyboard.c
index e96d0167fd4..923ac1ad1d9 100644
--- a/src/keyboard.c
+++ b/src/keyboard.c
@@ -5283,9 +5283,9 @@ make_lispy_position (struct frame *f, Lisp_Object x, Lisp_Object y,
           xret = XINT (x) - window_box_left (w, TEXT_AREA);
           yret = wy - WINDOW_HEADER_LINE_HEIGHT (w);
         }
-      /* For mode line and header line clicks, return X relative to
-         the left window edge; ignore Y.  Use mode_line_string to look
-         for a string on the click position.  */
+      /* For mode line and header line clicks, return X, Y relative to
+         the left window edge.  Use mode_line_string to look for a
+         string on the click position.  */
       else if (part == ON_MODE_LINE || part == ON_HEADER_LINE)
         {
           Lisp_Object string;
@@ -5305,6 +5305,7 @@ make_lispy_position (struct frame *f, Lisp_Object x, Lisp_Object y,
             ? PT : XMARKER (w->pointm)->charpos;
 
           xret = wx;
+          yret = wy;
         }
       /* For fringes and margins, Y is relative to the area's (and the
          window's) top edge, while X is meaningless.  */