From 1999c4cdc11c530be272d192c5b435a95cb6ba3b Mon Sep 17 00:00:00 2001
From: fredizzimo <fsundvik@gmail.com>
Date: Sat, 26 Apr 2025 23:39:12 +0300
Subject: [PATCH] fix: screenchar()/screenstring() with multigrid #32494

Problem:
- When multigrid is enabled, screenchar()/screenstring() functions return wrong
  results. See https://github.com/neovide/neovide/issues/2569
- `screenstring()` executed via RPC in child Nvim process, doesn't recognize
  floating windows.

Solution:
In ui_comp_get_grid_at_coord(), also iterate window grids.
---
 src/nvim/ui_compositor.c                      |  8 ++
 test/functional/vimscript/screenchar_spec.lua | 77 +++++++++++--------
 2 files changed, 52 insertions(+), 33 deletions(-)

diff --git a/src/nvim/ui_compositor.c b/src/nvim/ui_compositor.c
index e18e2a711d..afe64c15ae 100644
--- a/src/nvim/ui_compositor.c
+++ b/src/nvim/ui_compositor.c
@@ -333,6 +333,14 @@ ScreenGrid *ui_comp_get_grid_at_coord(int row, int col)
       return grid;
     }
   }
+
+  FOR_ALL_WINDOWS_IN_TAB(wp, curtab) {
+    ScreenGrid *grid = &wp->w_grid_alloc;
+    if (row >= grid->comp_row && row < grid->comp_row + grid->rows
+        && col >= grid->comp_col && col < grid->comp_col + grid->cols) {
+      return grid;
+    }
+  }
   return &default_grid;
 }
 
diff --git a/test/functional/vimscript/screenchar_spec.lua b/test/functional/vimscript/screenchar_spec.lua
index b6137d7741..706e3221c0 100644
--- a/test/functional/vimscript/screenchar_spec.lua
+++ b/test/functional/vimscript/screenchar_spec.lua
@@ -1,5 +1,6 @@
 local t = require('test.testutil')
 local n = require('test.functional.testnvim')()
+local Screen = require('test.functional.ui.screen')
 
 local clear, eq, neq = n.clear, t.eq, t.neq
 local command, api, fn = n.command, n.api, n.fn
@@ -30,42 +31,52 @@ local setup_floating_windows = function()
 end
 
 describe('screenchar() and family respect floating windows', function()
-  before_each(function()
-    clear()
-    -- These commands result into visible text `aabc`.
-    -- `aab` - from floating windows, `c` - from text in regular window.
-    api.nvim_buf_set_lines(0, 0, -1, true, { 'cccc' })
-    setup_floating_windows()
-  end)
+  local function with_ext_multigrid(multigrid)
+    before_each(function()
+      clear()
+      Screen.new(40, 7, { ext_multigrid = multigrid })
+      -- These commands result into visible text `aabc`.
+      -- `aab` - from floating windows, `c` - from text in regular window.
+      api.nvim_buf_set_lines(0, 0, -1, true, { 'cccc' })
+      setup_floating_windows()
+    end)
 
-  it('screenattr()', function()
-    local attr_1 = fn.screenattr(1, 1)
-    local attr_2 = fn.screenattr(1, 2)
-    local attr_3 = fn.screenattr(1, 3)
-    local attr_4 = fn.screenattr(1, 4)
-    eq(attr_1, attr_2)
-    eq(attr_1, attr_3)
-    neq(attr_1, attr_4)
-  end)
+    it('screenattr()', function()
+      local attr_1 = fn.screenattr(1, 1)
+      local attr_2 = fn.screenattr(1, 2)
+      local attr_3 = fn.screenattr(1, 3)
+      local attr_4 = fn.screenattr(1, 4)
+      eq(attr_1, attr_2)
+      eq(attr_1, attr_3)
+      neq(attr_1, attr_4)
+    end)
 
-  it('screenchar()', function()
-    eq(97, fn.screenchar(1, 1))
-    eq(97, fn.screenchar(1, 2))
-    eq(98, fn.screenchar(1, 3))
-    eq(99, fn.screenchar(1, 4))
-  end)
+    it('screenchar()', function()
+      eq(97, fn.screenchar(1, 1))
+      eq(97, fn.screenchar(1, 2))
+      eq(98, fn.screenchar(1, 3))
+      eq(99, fn.screenchar(1, 4))
+    end)
 
-  it('screenchars()', function()
-    eq({ 97 }, fn.screenchars(1, 1))
-    eq({ 97 }, fn.screenchars(1, 2))
-    eq({ 98 }, fn.screenchars(1, 3))
-    eq({ 99 }, fn.screenchars(1, 4))
-  end)
+    it('screenchars()', function()
+      eq({ 97 }, fn.screenchars(1, 1))
+      eq({ 97 }, fn.screenchars(1, 2))
+      eq({ 98 }, fn.screenchars(1, 3))
+      eq({ 99 }, fn.screenchars(1, 4))
+    end)
 
-  it('screenstring()', function()
-    eq('a', fn.screenstring(1, 1))
-    eq('a', fn.screenstring(1, 2))
-    eq('b', fn.screenstring(1, 3))
-    eq('c', fn.screenstring(1, 4))
+    it('screenstring()', function()
+      eq('a', fn.screenstring(1, 1))
+      eq('a', fn.screenstring(1, 2))
+      eq('b', fn.screenstring(1, 3))
+      eq('c', fn.screenstring(1, 4))
+    end)
+  end
+
+  describe('with ext_multigrid', function()
+    with_ext_multigrid(true)
+  end)
+  describe('without ext_multigrid', function()
+    with_ext_multigrid(false)
   end)
 end)