fix(ui): clamp 'cmdheight' for other tabpages on screen resize (#31419)

src/nvim/drawscreen.c

@@ -290,9 +290,23 @@ void screen_resize(int width, int height)
   Rows = height;
   Columns = width;
   check_screensize();
-  int max_p_ch = Rows - min_rows() + 1;
+  if (!ui_has(kUIMessages)) {
-  if (!ui_has(kUIMessages) && p_ch > 0 && p_ch > max_p_ch) {
+    // clamp 'cmdheight'
-    p_ch = max_p_ch ? max_p_ch : 1;
+    int max_p_ch = Rows - min_rows(curtab) + 1;
+    if (p_ch > 0 && p_ch > max_p_ch) {
+      p_ch = MAX(max_p_ch, 1);
+      curtab->tp_ch_used = p_ch;
+    }
+    // clamp 'cmdheight' for other tab pages
+    FOR_ALL_TABS(tp) {
+      if (tp == curtab) {
+        continue;  // already set above
+      }
+      int max_tp_ch = Rows - min_rows(tp) + 1;
+      if (tp->tp_ch_used > 0 && tp->tp_ch_used > max_tp_ch) {
+        tp->tp_ch_used = MAX(max_tp_ch, 1);
+      }
+    }
   }
   height = Rows;
   width = Columns;

src/nvim/option.c

@@ -1977,8 +1977,8 @@ static const char *did_set_cmdheight(optset_T *args)
 {
   OptInt old_value = args->os_oldval.number;
 
-  if (p_ch > Rows - min_rows() + 1) {
+  if (p_ch > Rows - min_rows(curtab) + 1) {
-    p_ch = Rows - min_rows() + 1;
+    p_ch = Rows - min_rows(curtab) + 1;
   }
 
   // if p_ch changed value, change the command line height

src/nvim/window.c

@@ -7065,17 +7065,17 @@ int last_stl_height(bool morewin)
 }
 
 /// Return the minimal number of rows that is needed on the screen to display
-/// the current number of windows.
+/// the current number of windows for the given tab page.
-int min_rows(void)
+int min_rows(tabpage_T *tp) FUNC_ATTR_NONNULL_ALL
 {
   if (firstwin == NULL) {       // not initialized yet
     return MIN_LINES;
   }
 
-  int total = frame_minheight(curtab->tp_topframe, NULL);
+  int total = frame_minheight(tp->tp_topframe, NULL);
   total += tabline_height() + global_stl_height();
-  if (p_ch > 0) {
+  if ((tp == curtab ? p_ch : tp->tp_ch_used) > 0) {
-    total += 1;           // count the room for the command line
+    total++;  // count the room for the command line
   }
   return total;
 }
@@ -7091,12 +7091,12 @@ int min_rows_for_all_tabpages(void)
   int total = 0;
   FOR_ALL_TABS(tp) {
     int n = frame_minheight(tp->tp_topframe, NULL);
+    if ((tp == curtab ? p_ch : tp->tp_ch_used) > 0) {
+      n++;  // count the room for the command line
+    }
     total = MAX(total, n);
   }
   total += tabline_height() + global_stl_height();
-  if (p_ch > 0) {
-    total += 1;           // count the room for the command line
-  }
   return total;
 }
 

test/functional/ui/screen_basic_spec.lua

@@ -645,6 +645,59 @@ local function screen_tests(linegrid)
                             |
       ]])
     end)
+
+    it('clamps &cmdheight for current tabpage', function()
+      command('set cmdheight=10 laststatus=2')
+      screen:expect([[
+        ^                                                     |
+        {0:~                                                    }|*2
+        {1:[No Name]                                            }|
+                                                             |*10
+      ]])
+      screen:try_resize(53, 8)
+      screen:expect([[
+        ^                                                     |
+        {1:[No Name]                                            }|
+                                                             |*6
+      ]])
+      eq(6, api.nvim_get_option_value('cmdheight', {}))
+    end)
+
+    it('clamps &cmdheight for another tabpage #31380', function()
+      command('tabnew')
+      command('set cmdheight=9 laststatus=2')
+      screen:expect([[
+        {4: [No Name] }{2: [No Name] }{3:                              }{4:X}|
+        ^                                                     |
+        {0:~                                                    }|*2
+        {1:[No Name]                                            }|
+                                                             |*9
+      ]])
+      command('tabprev')
+      screen:expect([[
+        {2: [No Name] }{4: [No Name] }{3:                              }{4:X}|
+        ^                                                     |
+        {0:~                                                    }|*10
+        {1:[No Name]                                            }|
+                                                             |
+      ]])
+      screen:try_resize(53, 8)
+      screen:expect([[
+        {2: [No Name] }{4: [No Name] }{3:                              }{4:X}|
+        ^                                                     |
+        {0:~                                                    }|*4
+        {1:[No Name]                                            }|
+                                                             |
+      ]])
+      command('tabnext')
+      screen:expect([[
+        {4: [No Name] }{2: [No Name] }{3:                              }{4:X}|
+        ^                                                     |
+        {1:[No Name]                                            }|
+                                                             |*5
+      ]])
+      eq(5, api.nvim_get_option_value('cmdheight', {}))
+    end)
   end)
 
   describe('press enter', function()