fix(clipboard): correct blockwise register width computation (#35038)

test/functional/api/vim_spec.lua

@@ -1573,6 +1573,17 @@ describe('API', function()
       eq("Invalid 'type': 'bx'", pcall_err(api.nvim_put, { 'xxx', 'yyy' }, 'bx', false, true))
       eq("Invalid 'type': 'b3x'", pcall_err(api.nvim_put, { 'xxx', 'yyy' }, 'b3x', false, true))
     end)
+
+    it('computes block width correctly when not specified #35034', function()
+      api.nvim_put({ 'line 1', 'line 2', 'line 3' }, 'l', false, false)
+      -- block width should be 4
+      api.nvim_put({ 'あい', 'xxx', 'xx' }, 'b', false, false)
+      expect([[
+        あいline 1
+        xxx line 2
+        xx  line 3
+        ]])
+    end)
   end)
 
   describe('nvim_strwidth', function()

test/functional/provider/clipboard_spec.lua

@@ -537,7 +537,7 @@ describe('clipboard (with fake clipboard.vim)', function()
       eq('textstar', api.nvim_get_current_line())
     end)
 
-    it('Block paste works correctly', function()
+    it('block paste works correctly', function()
       insert([[
         aabbcc
         ddeeff
@@ -550,6 +550,20 @@ describe('clipboard (with fake clipboard.vim)', function()
         ddeeddeeff
       ]])
     end)
+
+    it('block paste computes block width correctly #35034', function()
+      insert('あいうえお')
+      feed('0<C-V>ly')
+      feed('P')
+      expect('あいあいうえお')
+      feed('A\nxxx\nxx<Esc>')
+      feed('0<C-V>kkly')
+      feed('P')
+      expect([[
+        あいあいあいうえお
+        xxx xxx
+        xx  xx]])
+    end)
   end)
 
   describe('clipboard=unnamedplus', function()