[RDY] Fix click on foldcolumn if it has tabline (#13982)

* Fix click on foldcolumn if it has tabline
* Fixes to correctly determine if tablie was clicked when multigrid is enabled
* Separate foldcolumn checks into functions
* Add test case for click on foldcolumn with split window
* Fix foldcolumn click used nvim_input() on multigrid enabled

3 files changed, 413 insertions, 29 deletions

diff --git a/src/nvim/mouse.c b/src/nvim/mouse.c
index ff471ea978..f28658aa29 100644
--- a/src/nvim/mouse.c
+++ b/src/nvim/mouse.c
@@ -72,9 +72,7 @@ int jump_to_mouse(int flags,
   int row = mouse_row;
   int col = mouse_col;
   int grid = mouse_grid;
-  int mouse_char;
   int fdc = 0;
-  ScreenGrid *gp = &default_grid;
 
   mouse_past_bottom = false;
   mouse_past_eol = false;
@@ -303,25 +301,6 @@ retnomove:
     }
   }
 
-  // Remember the character under the mouse, might be one of foldclose or
-  // foldopen fillchars in the fold column.
-  if (ui_has(kUIMultigrid)) {
-    gp = &curwin->w_grid;
-  }
-  if (row >= 0 && row < Rows && col >= 0 && col <= Columns
-      && gp->chars != NULL) {
-    mouse_char = utf_ptr2char(gp->chars[gp->line_offset[row]
-                                        + (unsigned)col]);
-  } else {
-    mouse_char = ' ';
-  }
-
-  // Check for position outside of the fold column.
-  if (curwin->w_p_rl ? col < curwin->w_width_inner - fdc :
-      col >= fdc + (cmdwin_type == 0 ? 0 : 1)) {
-    mouse_char = ' ';
-  }
-
   // compute the position in the buffer line from the posn on the screen
   if (mouse_comp_pos(curwin, &row, &col, &curwin->w_cursor.lnum)) {
     mouse_past_bottom = true;
@@ -362,11 +341,7 @@ retnomove:
     count |= CURSOR_MOVED;              // Cursor has moved
   }
 
-  if (mouse_char == curwin->w_p_fcs_chars.foldclosed) {
-    count |= MOUSE_FOLD_OPEN;
-  } else if (mouse_char != ' ') {
-    count |= MOUSE_FOLD_CLOSE;
-  }
+  count |= mouse_check_fold();
 
   return count;
 }
@@ -738,3 +713,47 @@ static int mouse_adjust_click(win_T *wp, int row, int col)
 
   return col + nudge;
 }
+
+// Check clicked cell is foldcolumn
+int mouse_check_fold(void)
+{
+  int grid = mouse_grid;
+  int row = mouse_row;
+  int col = mouse_col;
+  int mouse_char = ' ';
+
+  win_T *wp;
+
+  wp = mouse_find_win(&grid, &row, &col);
+
+  if (wp && mouse_row >= 0 && mouse_row < Rows
+      && mouse_col >= 0 && mouse_col <= Columns) {
+    int multigrid = ui_has(kUIMultigrid);
+    ScreenGrid *gp = multigrid ? &wp->w_grid : &default_grid;
+    int fdc = win_fdccol_count(wp);
+
+    row = multigrid && mouse_grid == 0 ? row : mouse_row;
+    col = multigrid && mouse_grid == 0 ? col : mouse_col;
+
+    // Remember the character under the mouse, might be one of foldclose or
+    // foldopen fillchars in the fold column.
+    if (gp->chars != NULL) {
+      mouse_char = utf_ptr2char(gp->chars[gp->line_offset[row]
+                                          + (unsigned)col]);
+    }
+
+    // Check for position outside of the fold column.
+    if (wp->w_p_rl ? col < wp->w_width_inner - fdc :
+        col >= fdc + (cmdwin_type == 0 ? 0 : 1)) {
+      mouse_char = ' ';
+    }
+  }
+
+  if (mouse_char == wp->w_p_fcs_chars.foldclosed) {
+    return MOUSE_FOLD_OPEN;
+  } else if (mouse_char != ' ') {
+    return MOUSE_FOLD_CLOSE;
+  }
+
+  return 0;
+}
diff --git a/src/nvim/normal.c b/src/nvim/normal.c
index d5c92bc3e6..4d8b11f832 100644
--- a/src/nvim/normal.c
+++ b/src/nvim/normal.c
@@ -2404,8 +2404,8 @@ do_mouse (
 
   start_visual.lnum = 0;
 
-  /* Check for clicking in the tab page line. */
-  if (mouse_row == 0 && firstwin->w_winrow > 0) {
+  // Check for clicking in the tab page line.
+  if (mouse_grid <= 1 && mouse_row == 0 && firstwin->w_winrow > 0) {
     if (is_drag) {
       if (in_tab_line) {
         move_tab_to_mouse();
diff --git a/test/functional/ui/fold_spec.lua b/test/functional/ui/fold_spec.lua
index 6ce8b33a63..d3b1d33956 100644
--- a/test/functional/ui/fold_spec.lua
+++ b/test/functional/ui/fold_spec.lua
@@ -38,7 +38,9 @@ describe("folded lines", function()
         [6] = {background = Screen.colors.Yellow},
         [7] = {foreground = Screen.colors.DarkBlue, background = Screen.colors.WebGray},
         [8] = {foreground = Screen.colors.Brown },
-        [9] = {bold = true, foreground = Screen.colors.Brown}
+        [9] = {bold = true, foreground = Screen.colors.Brown},
+        [10] = {background = Screen.colors.LightGrey, underline = true},
+        [11] = {bold=true},
       })
     end)
 
@@ -290,6 +292,369 @@ describe("folded lines", function()
       end
     end)
 
+    it("works with split", function()
+      insert([[
+        aa
+        bb
+        cc
+        dd
+        ee
+        ff]])
+      feed_command('2')
+      command("set foldcolumn=1")
+      feed('zf3j')
+      feed_command('1')
+      feed('zf2j')
+      feed('zO')
+      feed_command("rightbelow new")
+      insert([[
+        aa
+        bb
+        cc
+        dd
+        ee
+        ff]])
+      feed_command('2')
+      command("set foldcolumn=1")
+      feed('zf3j')
+      feed_command('1')
+      feed('zf2j')
+      if multigrid then
+        meths.input_mouse('left', 'press', '', 4, 0, 0)
+        screen:expect([[
+        ## grid 1
+          [2:---------------------------------------------]|
+          [2:---------------------------------------------]|
+          {2:[No Name] [+]                                }|
+          [4:---------------------------------------------]|
+          [4:---------------------------------------------]|
+          [4:---------------------------------------------]|
+          {3:[No Name] [+]                                }|
+          [3:---------------------------------------------]|
+        ## grid 2
+          {7:-}aa                                          |
+          {7:-}bb                                          |
+        ## grid 3
+          :1                                           |
+        ## grid 4
+          {7:-}^aa                                          |
+          {7:+}{5:+---  4 lines: bb···························}|
+          {7:│}ff                                          |
+        ]])
+      else
+        meths.input_mouse('left', 'press', '', 0, 3, 0)
+        screen:expect([[
+          {7:-}aa                                          |
+          {7:-}bb                                          |
+          {2:[No Name] [+]                                }|
+          {7:-}^aa                                          |
+          {7:+}{5:+---  4 lines: bb···························}|
+          {7:│}ff                                          |
+          {3:[No Name] [+]                                }|
+          :1                                           |
+        ]])
+      end
+
+      if multigrid then
+        meths.input_mouse('left', 'press', '', 4, 1, 0)
+        screen:expect([[
+        ## grid 1
+          [2:---------------------------------------------]|
+          [2:---------------------------------------------]|
+          {2:[No Name] [+]                                }|
+          [4:---------------------------------------------]|
+          [4:---------------------------------------------]|
+          [4:---------------------------------------------]|
+          {3:[No Name] [+]                                }|
+          [3:---------------------------------------------]|
+        ## grid 2
+          {7:-}aa                                          |
+          {7:-}bb                                          |
+        ## grid 3
+          :1                                           |
+        ## grid 4
+          {7:-}^aa                                          |
+          {7:-}bb                                          |
+          {7:2}cc                                          |
+        ]])
+      else
+        meths.input_mouse('left', 'press', '', 0, 4, 0)
+        screen:expect([[
+          {7:-}aa                                          |
+          {7:-}bb                                          |
+          {2:[No Name] [+]                                }|
+          {7:-}^aa                                          |
+          {7:-}bb                                          |
+          {7:2}cc                                          |
+          {3:[No Name] [+]                                }|
+          :1                                           |
+        ]])
+      end
+
+      if multigrid then
+        meths.input_mouse('left', 'press', '', 2, 1, 0)
+        screen:expect([[
+        ## grid 1
+          [2:---------------------------------------------]|
+          [2:---------------------------------------------]|
+          {3:[No Name] [+]                                }|
+          [4:---------------------------------------------]|
+          [4:---------------------------------------------]|
+          [4:---------------------------------------------]|
+          {2:[No Name] [+]                                }|
+          [3:---------------------------------------------]|
+        ## grid 2
+          {7:-}aa                                          |
+          {7:+}{5:^+---  4 lines: bb···························}|
+        ## grid 3
+          :1                                           |
+        ## grid 4
+          {7:-}aa                                          |
+          {7:-}bb                                          |
+          {7:2}cc                                          |
+        ]])
+      else
+        meths.input_mouse('left', 'press', '', 0, 1, 0)
+        screen:expect([[
+          {7:-}aa                                          |
+          {7:+}{5:^+---  4 lines: bb···························}|
+          {3:[No Name] [+]                                }|
+          {7:-}aa                                          |
+          {7:-}bb                                          |
+          {7:2}cc                                          |
+          {2:[No Name] [+]                                }|
+          :1                                           |
+        ]])
+      end
+
+      if multigrid then
+        meths.input_mouse('left', 'press', '', 2, 0, 0)
+        screen:expect([[
+        ## grid 1
+          [2:---------------------------------------------]|
+          [2:---------------------------------------------]|
+          {3:[No Name] [+]                                }|
+          [4:---------------------------------------------]|
+          [4:---------------------------------------------]|
+          [4:---------------------------------------------]|
+          {2:[No Name] [+]                                }|
+          [3:---------------------------------------------]|
+        ## grid 2
+          {7:+}{5:^+--  6 lines: aa····························}|
+          {1:~                                            }|
+        ## grid 3
+          :1                                           |
+        ## grid 4
+          {7:-}aa                                          |
+          {7:-}bb                                          |
+          {7:2}cc                                          |
+        ]])
+      else
+        meths.input_mouse('left', 'press', '', 0, 0, 0)
+        screen:expect([[
+          {7:+}{5:^+--  6 lines: aa····························}|
+          {1:~                                            }|
+          {3:[No Name] [+]                                }|
+          {7:-}aa                                          |
+          {7:-}bb                                          |
+          {7:2}cc                                          |
+          {2:[No Name] [+]                                }|
+          :1                                           |
+        ]])
+      end
+    end)
+
+    it("works with tab", function()
+      insert([[
+        aa
+        bb
+        cc
+        dd
+        ee
+        ff]])
+      feed_command('2')
+      command("set foldcolumn=2")
+      feed('zf3j')
+      feed_command('1')
+      feed('zf2j')
+      feed('zO')
+      feed_command("tab split")
+      if multigrid then
+        meths.input_mouse('left', 'press', '', 4, 1, 1)
+        screen:expect([[
+        ## grid 1
+          {10: + [No Name] }{11: + [No Name] }{2:                  }{10:X}|
+          [4:---------------------------------------------]|
+          [4:---------------------------------------------]|
+          [4:---------------------------------------------]|
+          [4:---------------------------------------------]|
+          [4:---------------------------------------------]|
+          [4:---------------------------------------------]|
+          [3:---------------------------------------------]|
+        ## grid 2 (hidden)
+          {7:- }aa                                         |
+          {7:│-}bb                                         |
+          {7:││}cc                                         |
+          {7:││}dd                                         |
+          {7:││}ee                                         |
+          {7:│ }ff                                         |
+          {1:~                                            }|
+        ## grid 3
+          :tab split                                   |
+        ## grid 4
+          {7:- }^aa                                         |
+          {7:│+}{5:+---  4 lines: bb··························}|
+          {7:│ }ff                                         |
+          {1:~                                            }|
+          {1:~                                            }|
+          {1:~                                            }|
+        ]])
+      else
+        meths.input_mouse('left', 'press', '', 0, 2, 1)
+        screen:expect([[
+          {10: + [No Name] }{11: + [No Name] }{2:                  }{10:X}|
+          {7:- }^aa                                         |
+          {7:│+}{5:+---  4 lines: bb··························}|
+          {7:│ }ff                                         |
+          {1:~                                            }|
+          {1:~                                            }|
+          {1:~                                            }|
+          :tab split                                   |
+        ]])
+      end
+
+      if multigrid then
+        meths.input_mouse('left', 'press', '', 4, 0, 0)
+        screen:expect([[
+        ## grid 1
+          {10: + [No Name] }{11: + [No Name] }{2:                  }{10:X}|
+          [4:---------------------------------------------]|
+          [4:---------------------------------------------]|
+          [4:---------------------------------------------]|
+          [4:---------------------------------------------]|
+          [4:---------------------------------------------]|
+          [4:---------------------------------------------]|
+          [3:---------------------------------------------]|
+        ## grid 2 (hidden)
+          {7:- }aa                                         |
+          {7:│-}bb                                         |
+          {7:││}cc                                         |
+          {7:││}dd                                         |
+          {7:││}ee                                         |
+          {7:│ }ff                                         |
+          {1:~                                            }|
+        ## grid 3
+          :tab split                                   |
+        ## grid 4
+          {7:+ }{5:^+--  6 lines: aa···························}|
+          {1:~                                            }|
+          {1:~                                            }|
+          {1:~                                            }|
+          {1:~                                            }|
+          {1:~                                            }|
+        ]])
+      else
+        meths.input_mouse('left', 'press', '', 0, 1, 0)
+        screen:expect([[
+          {10: + [No Name] }{11: + [No Name] }{2:                  }{10:X}|
+          {7:+ }{5:^+--  6 lines: aa···························}|
+          {1:~                                            }|
+          {1:~                                            }|
+          {1:~                                            }|
+          {1:~                                            }|
+          {1:~                                            }|
+          :tab split                                   |
+        ]])
+      end
+
+      feed_command("tabnext")
+      if multigrid then
+        meths.input_mouse('left', 'press', '', 2, 1, 1)
+        screen:expect([[
+        ## grid 1
+          {11: + [No Name] }{10: + [No Name] }{2:                  }{10:X}|
+          [2:---------------------------------------------]|
+          [2:---------------------------------------------]|
+          [2:---------------------------------------------]|
+          [2:---------------------------------------------]|
+          [2:---------------------------------------------]|
+          [2:---------------------------------------------]|
+          [3:---------------------------------------------]|
+        ## grid 2
+          {7:- }^aa                                         |
+          {7:│+}{5:+---  4 lines: bb··························}|
+          {7:│ }ff                                         |
+          {1:~                                            }|
+          {1:~                                            }|
+          {1:~                                            }|
+        ## grid 3
+          :tabnext                                     |
+        ## grid 4 (hidden)
+          {7:+ }{5:+--  6 lines: aa···························}|
+          {1:~                                            }|
+          {1:~                                            }|
+          {1:~                                            }|
+          {1:~                                            }|
+          {1:~                                            }|
+        ]])
+      else
+        meths.input_mouse('left', 'press', '', 0, 2, 1)
+        screen:expect([[
+          {11: + [No Name] }{10: + [No Name] }{2:                  }{10:X}|
+          {7:- }^aa                                         |
+          {7:│+}{5:+---  4 lines: bb··························}|
+          {7:│ }ff                                         |
+          {1:~                                            }|
+          {1:~                                            }|
+          {1:~                                            }|
+          :tabnext                                     |
+        ]])
+      end
+
+      if multigrid then
+        meths.input_mouse('left', 'press', '', 2, 0, 0)
+        screen:expect([[
+        ## grid 1
+          {11: + [No Name] }{10: + [No Name] }{2:                  }{10:X}|
+          [2:---------------------------------------------]|
+          [2:---------------------------------------------]|
+          [2:---------------------------------------------]|
+          [2:---------------------------------------------]|
+          [2:---------------------------------------------]|
+          [2:---------------------------------------------]|
+          [3:---------------------------------------------]|
+        ## grid 2
+          {7:+ }{5:^+--  6 lines: aa···························}|
+          {1:~                                            }|
+          {1:~                                            }|
+          {1:~                                            }|
+          {1:~                                            }|
+          {1:~                                            }|
+        ## grid 3
+          :tabnext                                     |
+        ## grid 4 (hidden)
+          {7:+ }{5:+--  6 lines: aa···························}|
+          {1:~                                            }|
+          {1:~                                            }|
+          {1:~                                            }|
+          {1:~                                            }|
+          {1:~                                            }|
+        ]])
+      else
+        meths.input_mouse('left', 'press', '', 0, 1, 0)
+        screen:expect([[
+          {11: + [No Name] }{10: + [No Name] }{2:                  }{10:X}|
+          {7:+ }{5:^+--  6 lines: aa···························}|
+          {1:~                                            }|
+          {1:~                                            }|
+          {1:~                                            }|
+          {1:~                                            }|
+          {1:~                                            }|
+          :tabnext                                     |
+        ]])
+      end
+    end)
+
     it("works with multibyte text", function()
       -- Currently the only allowed value of 'maxcombine'
       eq(6, meths.get_option('maxcombine'))