patch 9.0.1919: Wrong curswant when clicking on empty line or with vsplits

Problem:  Wrong curswant when clicking on empty line or with vsplits.
Solution: Don't check for ScreenCols[] before the start of the window
          and handle empty line properly.

closes: #13132

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

src/mouse.c

@@ -2101,11 +2101,11 @@ retnomove:
     if (col_from_screen == MAXCOL)
     {
 	// When clicking after end of line, still need to set correct curswant
-	int off_l = LineOffset[prev_row];
+	int off_l = LineOffset[prev_row] + curwin->w_wincol;
 	if (ScreenCols[off_l] < MAXCOL)
 	{
 	    // Binary search to find last char in line
-	    int off_r = off_l + prev_col;
+	    int off_r = LineOffset[prev_row] + prev_col;
 	    int off_click = off_r;
 	    while (off_l < off_r)
 	    {
@@ -2118,8 +2118,8 @@ retnomove:
 	    col = ScreenCols[off_r] + (off_click - off_r);
 	}
 	else
-	    // Shouldn't normally happen
-	    col = MAXCOL;
+	    // Clicking on an empty line
+	    col = prev_col - curwin->w_wincol;
     }
     else if (col_from_screen >= 0)
     {

src/testdir/test_normal.vim

@@ -4104,6 +4104,39 @@ func Test_normal_click_on_double_width_char()
   let &mouse = save_mouse
 endfunc
 
+func Test_normal_click_on_empty_line()
+  let save_mouse = &mouse
+  set mouse=a
+  botright new
+  call setline(1, ['', '', ''])
+  let row = win_screenpos(0)[0] + 2
+  20vsplit
+  redraw
+
+  call test_setmouse(row, 1)
+  call feedkeys("\<LeftMouse>", 'xt')
+  call assert_equal([0, 3, 1, 0, 1], getcurpos())
+  call test_setmouse(row, 2)
+  call feedkeys("\<LeftMouse>", 'xt')
+  call assert_equal([0, 3, 1, 0, 2], getcurpos())
+  call test_setmouse(row, 10)
+  call feedkeys("\<LeftMouse>", 'xt')
+  call assert_equal([0, 3, 1, 0, 10], getcurpos())
+
+  call test_setmouse(row, 21 + 1)
+  call feedkeys("\<LeftMouse>", 'xt')
+  call assert_equal([0, 3, 1, 0, 1], getcurpos())
+  call test_setmouse(row, 21 + 2)
+  call feedkeys("\<LeftMouse>", 'xt')
+  call assert_equal([0, 3, 1, 0, 2], getcurpos())
+  call test_setmouse(row, 21 + 10)
+  call feedkeys("\<LeftMouse>", 'xt')
+  call assert_equal([0, 3, 1, 0, 10], getcurpos())
+
+  bwipe!
+  let &mouse = save_mouse
+endfunc
+
 func Test_normal33_g_cmd_nonblank()
   " Test that g<End> goes to the last non-blank char and g$ to the last
   " visible column

src/testdir/test_virtualedit.vim

@@ -564,35 +564,38 @@ func Test_virtualedit_mouse()
   let save_mouse = &mouse
   set mouse=a
   set virtualedit=all
-  new
+  botright new
+  let row = win_screenpos(0)[0]
+  20vsplit
+  wincmd p
 
   call setline(1, ["text\tword"])
   redraw
-  call test_setmouse(1, 4)
+  call test_setmouse(row, 21 + 4)
   call feedkeys("\<LeftMouse>", "xt")
   call assert_equal([0, 1, 4, 0, 4], getcurpos())
-  call test_setmouse(1, 5)
+  call test_setmouse(row, 21 + 5)
   call feedkeys("\<LeftMouse>", "xt")
   call assert_equal([0, 1, 5, 0, 5], getcurpos())
-  call test_setmouse(1, 6)
+  call test_setmouse(row, 21 + 6)
   call feedkeys("\<LeftMouse>", "xt")
   call assert_equal([0, 1, 5, 1, 6], getcurpos())
-  call test_setmouse(1, 7)
+  call test_setmouse(row, 21 + 7)
   call feedkeys("\<LeftMouse>", "xt")
   call assert_equal([0, 1, 5, 2, 7], getcurpos())
-  call test_setmouse(1, 8)
+  call test_setmouse(row, 21 + 8)
   call feedkeys("\<LeftMouse>", "xt")
   call assert_equal([0, 1, 5, 3, 8], getcurpos())
-  call test_setmouse(1, 9)
+  call test_setmouse(row, 21 + 9)
   call feedkeys("\<LeftMouse>", "xt")
   call assert_equal([0, 1, 6, 0, 9], getcurpos())
-  call test_setmouse(1, 12)
+  call test_setmouse(row, 21 + 12)
   call feedkeys("\<LeftMouse>", "xt")
   call assert_equal([0, 1, 9, 0, 12], getcurpos())
-  call test_setmouse(1, 13)
+  call test_setmouse(row, 21 + 13)
   call feedkeys("\<LeftMouse>", "xt")
   call assert_equal([0, 1, 10, 0, 13], getcurpos())
-  call test_setmouse(1, 15)
+  call test_setmouse(row, 21 + 15)
   call feedkeys("\<LeftMouse>", "xt")
   call assert_equal([0, 1, 10, 2, 15], getcurpos())
 

src/version.c

@@ -699,6 +699,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1919,
 /**/
     1918,
 /**/