patch 9.1.0406: Divide by zero with getmousepos() and 'smoothscroll'

Problem:  Divide by zero with getmousepos() and 'smoothscroll'.
Solution: Don't compute skip_lines when width1 is zero.
          (zeertzjq)

closes: #14747

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/mouse.c

@@ -3029,16 +3029,22 @@ mouse_comp_pos(
 
 	if (win->w_skipcol > 0 && lnum == win->w_topline)
 	{
-	    // Adjust for 'smoothscroll' clipping the top screen lines.
-	    // A similar formula is used in curs_columns().
 	    int width1 = win->w_width - win_col_off(win);
-	    int skip_lines = 0;
-	    if (win->w_skipcol > width1)
-		skip_lines = (win->w_skipcol - width1)
+
+	    if (width1 > 0)
+	    {
+		int skip_lines = 0;
+
+		// Adjust for 'smoothscroll' clipping the top screen lines.
+		// A similar formula is used in curs_columns().
+		if (win->w_skipcol > width1)
+		    skip_lines = (win->w_skipcol - width1)
 					    / (width1 + win_col_off2(win)) + 1;
-	    else if (win->w_skipcol > 0)
-		skip_lines = 1;
-	    count -= skip_lines;
+		else if (win->w_skipcol > 0)
+		    skip_lines = 1;
+
+		count -= skip_lines;
+	    }
 	}
 
 	if (count > row)

src/move.c

@@ -2617,12 +2617,14 @@ scroll_cursor_bot(int min_scroll, int set_topbot)
 			    plines_win
 #endif
 					(curwin, curwin->w_topline, FALSE);
-	    int skip_lines = 0;
 	    int width1 = curwin->w_width - curwin_col_off();
+
 	    if (width1 > 0)
 	    {
 		int width2 = width1 + curwin_col_off2();
-		// similar formula is used in curs_columns()
+		int skip_lines = 0;
+
+		// A similar formula is used in curs_columns().
 		if (curwin->w_skipcol > width1)
 		    skip_lines += (curwin->w_skipcol - width1) / width2 + 1;
 		else if (curwin->w_skipcol > 0)

src/testdir/test_functions.vim

@@ -3697,6 +3697,73 @@ func Test_getmousepos()
         \ column: 8,
         \ coladd: 21,
         \ }, getmousepos())
+
+  30vnew
+  setlocal smoothscroll number
+  call setline(1, join(range(100)))
+  exe "normal! \<C-E>"
+  call test_setmouse(1, 5)
+  call assert_equal(#{
+        \ screenrow: 1,
+        \ screencol: 5,
+        \ winid: win_getid(),
+        \ winrow: 1,
+        \ wincol: 5,
+        \ line: 1,
+        \ column: 27,
+        \ coladd: 0,
+        \ }, getmousepos())
+  call test_setmouse(2, 5)
+  call assert_equal(#{
+        \ screenrow: 2,
+        \ screencol: 5,
+        \ winid: win_getid(),
+        \ winrow: 2,
+        \ wincol: 5,
+        \ line: 1,
+        \ column: 53,
+        \ coladd: 0,
+        \ }, getmousepos())
+
+  exe "normal! \<C-E>"
+  call test_setmouse(1, 5)
+  call assert_equal(#{
+        \ screenrow: 1,
+        \ screencol: 5,
+        \ winid: win_getid(),
+        \ winrow: 1,
+        \ wincol: 5,
+        \ line: 1,
+        \ column: 53,
+        \ coladd: 0,
+        \ }, getmousepos())
+  call test_setmouse(2, 5)
+  call assert_equal(#{
+        \ screenrow: 2,
+        \ screencol: 5,
+        \ winid: win_getid(),
+        \ winrow: 2,
+        \ wincol: 5,
+        \ line: 1,
+        \ column: 79,
+        \ coladd: 0,
+        \ }, getmousepos())
+
+  vert resize 4
+  call test_setmouse(2, 2)
+  " This used to crash Vim
+  call assert_equal(#{
+        \ screenrow: 2,
+        \ screencol: 2,
+        \ winid: win_getid(),
+        \ winrow: 2,
+        \ wincol: 2,
+        \ line: 1,
+        \ column: 53,
+        \ coladd: 0,
+        \ }, getmousepos())
+
+  bwipe!
   bwipe!
 endfunc
 

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    406,
 /**/
     405,
 /**/