vim-patch:8.1.2304: cannot get the mouse position when getting a mouse click

Problem:    Cannot get the mouse position when getting a mouse click.
Solution:   Add getmousepos().
db3a205147

runtime/doc/eval.txt

@@ -2431,6 +2431,7 @@ getloclist({nr})		List	list of location list items
 getloclist({nr}, {what})	Dict	get specific location list properties
 getmarklist([{buf}])		List	list of global/local marks
 getmatches([{win}])		List	list of current matches
+getmousepos()			Dict	last known mouse position
 getpid()			Number	process ID of Vim
 getpos({expr})			List	position of cursor, mark, etc.
 getqflist()			List	list of quickfix items
@@ -4709,7 +4710,8 @@ getchar([expr])						*getchar()*
 		When the user clicks a mouse button, the mouse event will be
 		returned.  The position can then be found in |v:mouse_col|,
 		|v:mouse_lnum|, |v:mouse_winid| and |v:mouse_win|.
-		Mouse move events will be ignored.
+		|getmousepos()| can also be used.  Mouse move events will be
+		ignored.
 		This example positions the mouse as it would normally happen: >
 			let c = getchar()
 			if c == "\<LeftMouse>" && v:mouse_win > 0
@@ -5099,6 +5101,36 @@ getmatches([{win}])					*getmatches()*
 			'pattern': 'FIXME', 'priority': 10, 'id': 2}] >
 			:unlet m
 <
+getmousepos()						*getmousepos()*
+		Returns a Dictionary with the last known position of the
+		mouse.  This can be used in a mapping for a mouse click.  The
+		items are:
+			screenrow	screen row
+			screencol	screen column
+			winid		Window ID of the click
+			winrow		row inside "winid"
+			wincol		column inside "winid"
+			line		text line inside "winid"
+			column		text column inside "winid"
+		All numbers are 1-based.
+
+		If not over a window, e.g. when in the command line, then only
+		"screenrow" and "screencol" are valid, the others are zero.
+
+		When on the status line below a window or the vertical
+		separater right of a window, the "line" and "column" values
+		are zero.
+
+		When the position is after the text then "column" is the
+		length of the text in bytes.
+
+		If the mouse is over a focusable floating window then that
+		window is used.
+
+
+		When using |getchar()| the Vim variables |v:mouse_lnum|,
+		|v:mouse_col| and |v:mouse_winid| also provide these values.
+
 							*getpid()*
 getpid()	Return a Number which is the process ID of the Vim process.
 		This is a unique number, until Vim exits.

src/nvim/eval.lua

@@ -162,6 +162,7 @@ return {
     getloclist={args={1, 2}},
     getmarklist={args={0, 1}},
     getmatches={args={0, 1}},
+    getmousepos={},
     getpid={},
     getpos={args=1},
     getqflist={args={0, 1}},

src/nvim/eval/funcs.c

@@ -3750,6 +3750,48 @@ static void f_getmatches(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   }
 }
 
+// "getmousepos()" function
+void f_getmousepos(typval_T *argvars, typval_T *rettv, FunPtr fptr)
+{
+  dict_T *d;
+  win_T *wp;
+  int row = mouse_row;
+  int col = mouse_col;
+  int grid = mouse_grid;
+  varnumber_T winid = 0;
+  varnumber_T winrow = 0;
+  varnumber_T wincol = 0;
+  varnumber_T line = 0;
+  varnumber_T column = 0;
+
+  tv_dict_alloc_ret(rettv);
+  d = rettv->vval.v_dict;
+
+  tv_dict_add_nr(d, S_LEN("screenrow"), (varnumber_T)mouse_row + 1);
+  tv_dict_add_nr(d, S_LEN("screencol"), (varnumber_T)mouse_col + 1);
+
+  wp = mouse_find_win(&grid, &row, &col);
+  if (wp != NULL) {
+    int height = wp->w_height + wp->w_status_height;
+    // The height is adjusted by 1 when there is a bottom border. This is not
+    // necessary for a top border since `row` starts at -1 in that case.
+    if (row < height + wp->w_border_adj[2]) {
+      winid = wp->handle;
+      winrow = row + 1 + wp->w_border_adj[0];  // Adjust by 1 for top border
+      wincol = col + 1 + wp->w_border_adj[3];  // Adjust by 1 for left border
+      if (row >= 0 && row < wp->w_height && col >= 0 && col < wp->w_width) {
+        mouse_comp_pos(wp, &row, &col, &line);
+        column = col + 1;
+      }
+    }
+  }
+  tv_dict_add_nr(d, S_LEN("winid"), winid);
+  tv_dict_add_nr(d, S_LEN("winrow"), winrow);
+  tv_dict_add_nr(d, S_LEN("wincol"), wincol);
+  tv_dict_add_nr(d, S_LEN("line"), line);
+  tv_dict_add_nr(d, S_LEN("column"), column);
+}
+
 /*
  * "getpid()" function
  */

src/nvim/mouse.c

@@ -363,6 +363,7 @@ bool mouse_comp_pos(win_T *win, int *rowp, int *colp, linenr_T *lnump)
   bool retval = false;
   int off;
   int count;
+  char_u *p;
 
   if (win->w_p_rl) {
     col = win->w_width_inner - 1 - col;
@@ -407,6 +408,12 @@ bool mouse_comp_pos(win_T *win, int *rowp, int *colp, linenr_T *lnump)
     col += row * (win->w_width_inner - off);
     // add skip column (for long wrapping line)
     col += win->w_skipcol;
+    // limit to text length plus one
+    p = ml_get_buf(win->w_buffer, lnum, false);
+    count = STRLEN(p);
+    if (col > count) {
+      col = count;
+    }
   }
 
   if (!win->w_p_wrap) {