fix(float): clamp floating window above cmdline #37899

Problem:  A float whose zindex is below the cmdline can be enlarged and
          end up behind the cmdline.
Solution: Clamp height of such windows to not extend beyond 'cmdheight'.

src/nvim/winfloat.c

@@ -239,7 +239,8 @@ void win_config_float(win_T *wp, WinConfig fconfig)
   }
 
   if (!ui_has(kUIMultigrid)) {
-    wp->w_height = MIN(wp->w_height, Rows - win_border_height(wp));
+    int above_ch = wp->w_config.zindex < kZIndexMessages ? (int)p_ch : 0;
+    wp->w_height = MIN(wp->w_height, Rows - win_border_height(wp) - above_ch);
     wp->w_width = MIN(wp->w_width, Columns - win_border_width(wp));
   }
 

test/functional/ui/float_spec.lua

@@ -5028,9 +5028,9 @@ describe('float window', function()
         }
       else
         screen:expect([[
-                    {1:such           }               |
+                    {1:very           }               |
-          {0:~         }{1:very           }{0:               }|
+          {0:~         }{1:^float          }{0:               }|
-                    ^                              |
+                                                  |
         ]])
       end
 
@@ -10924,7 +10924,7 @@ describe('float window', function()
           {0:~    }{5:│}{2:~}{5:│}{2:~}{5:│┌──┐│}{2: }{5:││}{0:                      }|
           {0:~    }{5:│}{2:~}{5:│}{2:~}{5:││}{1:  }{5:││}{2: }{5:││}{0:                      }|
           {0:~    }{5:│}{2:~}{5:│}{2:~}{5:││}{2:~ }{5:││}{2: }{5:││}{0:                      }|
-          {0:~    }{5:│}{2:~}{5:│}{2:~}{5:└└──┘┘}{2: }{5:││}{0:                      }|
+          {0:~    }{5:└─└─└└──┘┘─┘┘}{0:                      }|
                                                   |
         ]])
       end
@@ -10966,7 +10966,7 @@ describe('float window', function()
           ^     {5:┌─┌─┌────┐─┐┐}                      |
           {0:~    }{5:│}{1: }{5:│}{1: }{5:│}{1:    }{5:│}{1: }{5:││}{0:                      }|
           {0:~    }{5:│}{2:~}{5:│}{2:~}{5:│}{2:~   }{5:│}{2: }{5:││}{0:                      }|*3
-          {0:~    }{5:│}{2:~}{5:│}{2:~}{5:└────┘}{2: }{5:││}{0:                      }|
+          {0:~    }{5:└─└─└────┘─┘┘}{0:                      }|
                                                   |
         ]])
       end
@@ -11002,7 +11002,8 @@ describe('float window', function()
         screen:expect([[
           ^     {5:┌─┌────────┐┐}                      |
           {0:~    }{5:│}{1: }{5:│}{1:        }{5:││}{0:                      }|
-          {0:~    }{5:│}{2:~}{5:│}{2:~       }{5:││}{0:                      }|*4
+          {0:~    }{5:│}{2:~}{5:│}{2:~       }{5:││}{0:                      }|*3
+          {0:~    }{5:└─└────────┘┘}{0:                      }|
                                                   |
         ]])
       end
@@ -11730,6 +11731,89 @@ describe('float window', function()
         screen:expect { mode = 'cmdline_normal' }
       end
     end)
+
+    it("window is not enlarged behind 'cmdheight'", function()
+      local opts = { relative = 'editor', width = 10, height = 4, row = 0, col = 0, zindex = 199 }
+      opts.border = 'single'
+      api.nvim_open_win(0, true, opts)
+      opts.zindex, opts.col = 200, 12
+      local above = api.nvim_open_win(0, false, opts)
+      command('echo "cmdline" | wincmd +')
+      if multigrid then
+        screen:expect({
+          grid = [[
+          ## grid 1
+            [2:----------------------------------------]|*6
+            [3:----------------------------------------]|
+          ## grid 2
+                                                    |
+            {0:~                                       }|*5
+          ## grid 3
+            cmdline                                 |
+          ## grid 4
+            {5:┌──────────┐}|
+            {5:│}{1:^          }{5:│}|
+            {5:│}{2:~         }{5:│}|*4
+            {5:└──────────┘}|
+          ## grid 5
+            {5:┌──────────┐}|
+            {5:│}{1:          }{5:│}|
+            {5:│}{2:~         }{5:│}|*3
+            {5:└──────────┘}|
+          ]],
+          float_pos = {
+            [5] = { 1002, 'NW', 1, 0, 12, true, 200, 3, 0, 12 },
+            [4] = { 1001, 'NW', 1, 0, 0, true, 199, 1, 0, 0 },
+          },
+        })
+      else
+        screen:expect([[
+          {5:┌──────────┐┌──────────┐}                |
+          {5:│}{1:^          }{5:││}{1:          }{5:│}{0:                }|
+          {5:│}{2:~         }{5:││}{2:~         }{5:│}{0:                }|*3
+          {5:└──────────┘└──────────┘}{0:                }|
+          cmdline                                 |
+        ]])
+      end
+      api.nvim_set_current_win(above)
+      command('wincmd +')
+      if multigrid then
+        screen:expect({
+          grid = [[
+          ## grid 1
+            [2:----------------------------------------]|*6
+            [3:----------------------------------------]|
+          ## grid 2
+                                                    |
+            {0:~                                       }|*5
+          ## grid 3
+            cmdline                                 |
+          ## grid 4
+            {5:┌──────────┐}|
+            {5:│}{1:          }{5:│}|
+            {5:│}{2:~         }{5:│}|*4
+            {5:└──────────┘}|
+          ## grid 5
+            {5:┌──────────┐}|
+            {5:│}{1:^          }{5:│}|
+            {5:│}{2:~         }{5:│}|*4
+            {5:└──────────┘}|
+          ]],
+          float_pos = {
+            [5] = { 1002, 'NW', 1, 0, 12, true, 200, 3, 0, 12 },
+            [4] = { 1001, 'NW', 1, 0, 0, true, 199, 1, 0, 0 },
+          },
+        })
+      else
+        screen:expect([[
+          {5:┌──────────┐┌──────────┐}                |
+          {5:│}{1:          }{5:││}{1:^          }{5:│}{0:                }|
+          {5:│}{2:~         }{5:││}{2:~         }{5:│}{0:                }|*3
+          {5:└──────────┘│}{2:~         }{5:│}{0:                }|
+          cmdline     {5:└──────────┘}                |
+        ]])
+      end
+    end)
   end
 
   describe('with ext_multigrid and actual mouse grid', function()