@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.
@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
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:
usual meaning is a kind of scroll or zoom.
The element @var{position} is a list describing the position of the
-event, in the same format as used in a mouse-click event.
+event, in the same format as used in a mouse-click event (@pxref{Click
+Events}).
@vindex mouse-wheel-up-event
@vindex mouse-wheel-down-event
dropped onto an Emacs frame.
The element @var{position} is a list describing the position of the
-event, in the same format as used in a mouse-click event, and
-@var{files} is the list of file names that were dragged and dropped.
-The usual way to handle this event is by visiting these files.
+event, in the same format as used in a mouse-click event (@pxref{Click
+Events}), and @var{files} is the list of file names that were dragged
+and dropped. The usual way to handle this event is by visiting these
+files.
This kind of event is generated, at present, only on some kinds of
systems.