fix(mouse): click on empty line with 'foldcolumn'

src/nvim/mouse.c

@@ -1861,44 +1861,47 @@ static void mouse_check_grid(colnr_T *vcolp, int *flagsp)
   int start_row = 0;
   int start_col = 0;
   grid_adjust(&gp, &start_row, &start_col);
-  if (gp->handle != click_grid) {
+  if (gp->handle != click_grid || gp->chars == NULL) {
     return;
   }
   click_row += start_row;
   click_col += start_col;
+  if (click_row < 0 || click_row >= gp->rows
+      || click_col < 0 || click_col >= gp->cols) {
+    return;
+  }
 
-  colnr_T col_from_screen = -1;
+  const size_t off = gp->line_offset[click_row] + (size_t)click_col;
+  colnr_T col_from_screen = gp->vcols[off];
 
-  if (gp->chars != NULL
+  if (col_from_screen == MAXCOL) {
-      && click_row >= 0 && click_row < gp->rows
+    // When clicking after end of line, still need to set correct curswant
-      && click_col >= 0 && click_col < gp->cols) {
+    size_t off_l = gp->line_offset[click_row] + (size_t)start_col;
-    const size_t off = gp->line_offset[click_row] + (size_t)click_col;
+    if (gp->vcols[off_l] < MAXCOL) {
-    col_from_screen = gp->vcols[off];
+      // Binary search to find last char in line
-
+      size_t off_r = off;
-    if (col_from_screen == MAXCOL) {
+      while (off_l < off_r) {
-      // When clicking after end of line, still need to set correct curswant
+        size_t off_m = (off_l + off_r + 1) / 2;
-      size_t off_l = gp->line_offset[click_row] + (size_t)start_col;
+        if (gp->vcols[off_m] < MAXCOL) {
-      if (gp->vcols[off_l] < MAXCOL) {
+          off_l = off_m;
-        // Binary search to find last char in line
+        } else {
-        size_t off_r = off;
+          off_r = off_m - 1;
-        while (off_l < off_r) {
-          size_t off_m = (off_l + off_r + 1) / 2;
-          if (gp->vcols[off_m] < MAXCOL) {
-            off_l = off_m;
-          } else {
-            off_r = off_m - 1;
-          }
         }
-        *vcolp = gp->vcols[off_r] + (int)(off - off_r);
-      } else {
-        // Clicking on an empty line
-        *vcolp = click_col - start_col;
       }
-    } else if (col_from_screen >= 0) {
+      colnr_T eol_vcol = gp->vcols[off_r];
-      // Use the virtual column from vcols[], it is accurate also after
+      assert(eol_vcol < MAXCOL);
-      // concealed characters.
+      // This may be -2 or -3 with 'foldcolumn' and empty line.
-      *vcolp = col_from_screen;
+      // In that case set it to -1 as it's just before start of line.
+      eol_vcol = MAX(eol_vcol, -1);
+      *vcolp = eol_vcol + (int)(off - off_r);
+    } else {
+      // Clicking on an empty line
+      *vcolp = click_col - start_col;
     }
+  } else if (col_from_screen >= 0) {
+    // Use the virtual column from vcols[], it is accurate also after
+    // concealed characters.
+    *vcolp = col_from_screen;
   }
 
   if (col_from_screen == -2) {

test/functional/ui/float_spec.lua

@@ -8831,6 +8831,117 @@ describe('float window', function()
         meths.input_mouse('left', 'press', '', 0, 3, 15)
       end
       eq({0, 3, 1, 0, 10}, funcs.getcurpos())
+
+      command('setlocal foldcolumn=1')
+      feed('zfkgg')
+      if multigrid then
+        screen:expect{grid=[[
+        ## grid 1
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [3:----------------------------------------]|
+        ## grid 2
+                                                  |
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+        ## grid 3
+                                                  |
+        ## grid 4
+          {5:┌────────────────────┐}|
+          {5:│}{19: }{1:^                   }{5:│}|
+          {5:│}{19:+}{28:+--  2 lines: ·····}{5:│}|
+          {5:│}{2:~                   }{5:│}|
+          {5:└────────────────────┘}|
+        ]], float_pos={
+          [4] = {{id = 1001}, "NW", 1, 0, 5, true, 50};
+        }, win_viewport={
+          [2] = {win = {id = 1000}, topline = 0, botline = 2, curline = 0, curcol = 0, linecount = 1, sum_scroll_delta = 0};
+          [4] = {win = {id = 1001}, topline = 0, botline = 4, curline = 0, curcol = 0, linecount = 3, sum_scroll_delta = 0};
+        }}
+      else
+        screen:expect{grid=[[
+               {5:┌────────────────────┐}             |
+          {0:~    }{5:│}{19: }{1:^                   }{5:│}{0:             }|
+          {0:~    }{5:│}{19:+}{28:+--  2 lines: ·····}{5:│}{0:             }|
+          {0:~    }{5:│}{2:~                   }{5:│}{0:             }|
+          {0:~    }{5:└────────────────────┘}{0:             }|
+          {0:~                                       }|
+                                                  |
+        ]]}
+      end
+
+      if multigrid then
+        meths.input_mouse('left', 'press', '', 4, 2, 1)
+        screen:expect{grid=[[
+        ## grid 1
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [2:----------------------------------------]|
+          [3:----------------------------------------]|
+        ## grid 2
+                                                  |
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+          {0:~                                       }|
+        ## grid 3
+                                                  |
+        ## grid 4
+          {5:┌────────────────────┐}|
+          {5:│}{19: }{1:^                   }{5:│}|
+          {5:│}{19:-}{1:                   }{5:│}|
+          {5:│}{19:│}{1:                   }{5:│}|
+          {5:└────────────────────┘}|
+        ]], float_pos={
+          [4] = {{id = 1001}, "NW", 1, 0, 5, true, 50};
+        }, win_viewport={
+          [2] = {win = {id = 1000}, topline = 0, botline = 2, curline = 0, curcol = 0, linecount = 1, sum_scroll_delta = 0};
+          [4] = {win = {id = 1001}, topline = 0, botline = 3, curline = 0, curcol = 0, linecount = 3, sum_scroll_delta = 0};
+        }}
+      else
+        meths.input_mouse('left', 'press', '', 0, 2, 6)
+        screen:expect{grid=[[
+               {5:┌────────────────────┐}             |
+          {0:~    }{5:│}{19: }{1:^                   }{5:│}{0:             }|
+          {0:~    }{5:│}{19:-}{1:                   }{5:│}{0:             }|
+          {0:~    }{5:│}{19:│}{1:                   }{5:│}{0:             }|
+          {0:~    }{5:└────────────────────┘}{0:             }|
+          {0:~                                       }|
+                                                  |
+        ]]}
+      end
+
+      if multigrid then
+        meths.input_mouse('left', 'press', '', 4, 2, 2)
+      else
+        meths.input_mouse('left', 'press', '', 0, 2, 7)
+      end
+      eq({0, 2, 1, 0, 1}, funcs.getcurpos())
+
+      if multigrid then
+        meths.input_mouse('left', 'press', '', 4, 2, 3)
+      else
+        meths.input_mouse('left', 'press', '', 0, 2, 8)
+      end
+      eq({0, 2, 1, 0, 2}, funcs.getcurpos())
+
+      if multigrid then
+        meths.input_mouse('left', 'press', '', 4, 2, 11)
+      else
+        meths.input_mouse('left', 'press', '', 0, 2, 16)
+      end
+      eq({0, 2, 1, 0, 10}, funcs.getcurpos())
     end)
 
     it("'winblend' option", function()