Re: Moving point after character when clicking latter half of it

[Po Lu]

Moritz Maxeiner <mm@ucw.sh> writes:

> Done. Though I am concerned that capitalizing "x coordinate" to  "X 
> coordinate" will lead to confusion, as capitalized X seems to usually refer 
> to 
> the X window system within NEWS. In this instance, it's not supposed to be 
> referring to that, instead it's referring to the x of the (x,y) coordinate 
> pair.

I think that what the X refers to is sufficiently clear from the
surrounding context.  If you're still concerned, however, how about
``cordinate on the X axis''?

> diff --git a/doc/lispref/commands.texi b/doc/lispref/commands.texi
> index cd1745614eb..d1b8f9c494c 100644
> --- a/doc/lispref/commands.texi
> +++ b/doc/lispref/commands.texi
> @@ -2751,6 +2751,16 @@ If @var{whole} is non-@code{nil}, the @var{x} 
> coordinate is relative
>  to the entire window area including scroll bars, margins and fringes.
>  @end defun
>  
> +@defopt mouse-prefer-closest-glyph
> +If this variable is non-@code{nil}, the @code{posn-point} of a mouse
> +position list will be set to the position of the glyph whose left most
> +position is closest to the mouse pointer, as opposed to the position of
> +the glyph underneath the mouse pointer itself.  For example, if
> +@code{posn-at-x-y} is called with @var{x} set to @code{9}, which is
> +contained within a character of width 10 positioned at column 0, the
> +point saved within the mouse position list will be after that character.
> +@end defopt
> +
>  @node Accessing Scroll
>  @subsection Accessing Scroll Bar Events
>  @cindex scroll bar events, data in
> diff --git a/etc/NEWS b/etc/NEWS
> index 9e6f0c16bcd..3c127aa9bd7 100644
> --- a/etc/NEWS
> +++ b/etc/NEWS
> @@ -952,6 +952,17 @@ wheel reports.  Unlike 'pixel-scroll-mode', this mode 
> scrolls the
>  display pixel-by-pixel, as opposed to only animating line-by-line
>  scrolls.
>  
> ++++
> +** New user option 'mouse-prefer-closest-glyph'.
> +When enabled, clicking or dragging with the mouse will put the point
> +in front of the buffer position corresponding to the glyph with the
> +closest X coordinate to the click or start of the drag.
> +In other words, if the mouse pointer is in the right half of a glyph,
> +point will be put after the buffer position corresponding to that glyph,
> +whereas if the mouse pointer is in the left half of a glyph, point
> +will be put in front the buffer position corresponding to that glyph.
> +By default this is disabled.
> +
>  ** Terminal Emacs
>  
>  ---
> diff --git a/lisp/cus-start.el b/lisp/cus-start.el
> index 054683d7cf6..2ed904f178f 100644
> --- a/lisp/cus-start.el
> +++ b/lisp/cus-start.el
> @@ -231,6 +231,7 @@ Leaving \"Default\" unchecked is equivalent with 
> specifying a default of
>            (inverse-video display boolean)
>            (visible-bell display boolean)
>            (no-redraw-on-reenter display boolean)
> +          (mouse-prefer-closest-glyph display boolean)
>  
>               ;; doc.c
>               (text-quoting-style display
> diff --git a/src/dispnew.c b/src/dispnew.c
> index 65d9cf9b4e1..143dda412e9 100644
> --- a/src/dispnew.c
> +++ b/src/dispnew.c
> @@ -5611,6 +5611,15 @@ buffer_posn_from_coords (struct window *w, int *x, int 
> *y, struct display_pos *p
>       argument is ZV to prevent move_it_in_display_line from matching
>       based on buffer positions.  */
>    move_it_in_display_line (&it, ZV, to_x, MOVE_TO_X);
> +  if (mouse_prefer_closest_glyph)
> +    {
> +      int next_x = it.current_x + it.pixel_width;
> +      int before_dx = to_x - it.current_x;
> +      int after_dx = next_x - to_x;
> +      if (before_dx > after_dx)
> +        move_it_in_display_line (&it, ZV, next_x, MOVE_TO_X);
> +    }
> +
>    bidi_unshelve_cache (itdata, 0);
>  
>    Fset_buffer (old_current_buffer);
> @@ -6788,6 +6797,15 @@ predicates which report frame's specific UI-related 
> capabilities.  */);
>    DEFVAR_BOOL ("cursor-in-echo-area", cursor_in_echo_area,
>              doc: /* Non-nil means put cursor in minibuffer, at end of any 
> message there.  */);
>  
> +  DEFVAR_BOOL ("mouse-prefer-closest-glyph", mouse_prefer_closest_glyph,
> +            doc: /* Non-nil means mouse position lists are reported relative
> +to the glyph closest to their coordinates.
> +
> + When non-nil, mouse position lists will be reported with their
> +`posn-point' set to the position of the glyph closest to the mouse
> +pointer, instead of the glyph immediately under.  */);
> +  mouse_prefer_closest_glyph = false;
> +
>    DEFVAR_LISP ("glyph-table", Vglyph_table,
>              doc: /* Table defining how to output a glyph code to the frame.
>  If not nil, this is a vector indexed by glyph code to define the glyph.
> diff --git a/src/xdisp.c b/src/xdisp.c
> index 763af7d3bc8..1d71bb02641 100644
> --- a/src/xdisp.c
> +++ b/src/xdisp.c
> @@ -2723,6 +2723,7 @@ remember_mouse_glyph (struct frame *f, int gx, int gy, 
> NativeRectangle *rect)
>    enum window_part part;
>    enum glyph_row_area area;
>    int x, y, width, height;
> +  int original_gx;
>  
>    if (mouse_fine_grained_tracking)
>      {
> @@ -2733,6 +2734,8 @@ remember_mouse_glyph (struct frame *f, int gx, int gy, 
> NativeRectangle *rect)
>    /* Try to determine frame pixel position and size of the glyph under
>       frame pixel coordinates X/Y on frame F.  */
>  
> +  original_gx = gx;
> +
>    if (window_resize_pixelwise)
>      {
>        width = height = 1;
> @@ -2948,6 +2951,15 @@ remember_mouse_glyph (struct frame *f, int gx, int gy, 
> NativeRectangle *rect)
>    gy += WINDOW_TOP_EDGE_Y (w);
>  
>   store_rect:
> +  if (mouse_prefer_closest_glyph)
> +    {
> +      int half_width = width / 2;
> +      width = half_width;
> +
> +      int bisection = gx + half_width;
> +      if (original_gx > bisection)
> +        gx = bisection;
> +    }
>    STORE_NATIVE_RECT (*rect, gx, gy, width, height);
>  
>    /* Visible feedback for debugging.  */
> @@ -37345,7 +37357,10 @@ may be more familiar to users.  */);
>    DEFVAR_BOOL ("mouse-fine-grained-tracking", mouse_fine_grained_tracking,
>      doc: /* Non-nil for pixel-wise mouse-movement.
>  When nil, mouse-movement events will not be generated as long as the
> -mouse stays within the extent of a single glyph (except for images).  */);
> +mouse stays within the extent of a single glyph (except for images).
> +When nil and mouse-prefer-closest-glyph is non-nil, mouse-movement
> +events will instead not be generated as long as the mouse stays within
> +the extent of a single left/right half glyph (except for images).  */);
>    mouse_fine_grained_tracking = false;
>  
>    DEFVAR_BOOL ("tab-bar--dragging-in-progress", 
> tab_bar__dragging_in_progress,

Otherwise, LGTM.  Thanks.