feat(input)!: delay some conversions to vgetc()

src/nvim/getchar.c

@@ -1583,6 +1583,14 @@ int vgetc(void)
         c = utf_ptr2char(buf);
       }
 
+      if ((mod_mask & MOD_MASK_CTRL) && (c >= '?' && c <= '_')) {
+        c = Ctrl_chr(c);
+        mod_mask &= ~MOD_MASK_CTRL;
+        if (c == 0) {  // <C-@> is <Nul>
+          c = K_ZERO;
+        }
+      }
+
       // If mappings are enabled (i.e., not Ctrl-v) and the user directly typed
       // something with a meta- or alt- modifier that was not mapped, interpret
       // <M-x> as <Esc>x rather than as an unbound meta keypress. #8213

src/nvim/keymap.c

@@ -13,6 +13,7 @@
 #include "nvim/memory.h"
 #include "nvim/message.h"
 #include "nvim/mouse.h"
+#include "nvim/option_defs.h"
 #include "nvim/strings.h"
 #include "nvim/vim.h"
 
@@ -744,14 +745,17 @@ static int extract_modifiers(int key, int *modp)
       modifiers &= ~MOD_MASK_SHIFT;
     }
   }
-  if ((modifiers & MOD_MASK_CTRL)
-      && ((key >= '?' && key <= '_') || ASCII_ISALPHA(key))) {
-    key = Ctrl_chr(key);
+  if ((modifiers & MOD_MASK_CTRL) && ((key >= '?' && key <= '_') || ASCII_ISALPHA(key))) {
+    key = TOUPPER_ASC(key);
+    int new_key = Ctrl_chr(key);
+    if (!p_clbg || (new_key != TAB && new_key != CAR && new_key != ESC)) {
+      key = new_key;
       modifiers &= ~MOD_MASK_CTRL;
       if (key == 0) {  // <C-@> is <Nul>
         key = K_ZERO;
       }
     }
+  }
 
   *modp = modifiers;
   return key;

src/nvim/option_defs.h

@@ -401,6 +401,7 @@ EXTERN int p_cst;               // 'cscopetag'
 EXTERN long p_csto;             // 'cscopetagorder'
 EXTERN long p_cspc;             // 'cscopepathcomp'
 EXTERN int p_csverbose;         // 'cscopeverbose'
+EXTERN int p_clbg;            // 'ctrldisambig'
 EXTERN char_u *p_debug;       // 'debug'
 EXTERN char_u *p_def;         // 'define'
 EXTERN char_u *p_inc;

src/nvim/options.lua

@@ -541,6 +541,13 @@ return {
       varname='p_csverbose',
       defaults={if_true=1}
     },
+    {
+      full_name='ctrldisambig', abbreviation='clbg',
+      short_desc=N_(""),
+      type='bool', scope={'global'},
+      varname='p_clbg',
+      defaults={if_true=true}
+    },
     {
       full_name='cursorbind', abbreviation='crb',
       short_desc=N_("move cursor in window as it moves in other windows"),

src/nvim/testdir/setup.vim

@@ -14,6 +14,7 @@ set fsync
 set laststatus=1
 set listchars=eol:$
 set joinspaces
+set noctrldisambig
 set nohidden nosmarttab noautoindent noautoread complete-=i noruler noshowcmd
 set nrformats+=octal
 set shortmess-=F

test/functional/legacy/eval_spec.lua

@@ -35,7 +35,10 @@ describe('eval', function()
       endfun
       ]])
   end)
-  before_each(clear)
+  before_each(function()
+    clear()
+    command('set noctrldisambig')
+  end)
   teardown(function()
     os.remove('test_eval_setup.vim')
   end)