options: remove 'maxcombine` option (always use 6)

runtime/doc/mbyte.txt

@@ -1059,8 +1059,7 @@ widespread as file format.
 A composing or combining character is used to change the meaning of the
 character before it.  The combining characters are drawn on top of the
 preceding character.
-Up to two combining characters can be used by default.  This can be changed
-with the 'maxcombine' option.
+Up to six combining characters can be displayed.
 When editing text a composing character is mostly considered part of the
 preceding character.  For example "x" will delete a character and its
 following composing characters by default.

runtime/doc/options.txt

@@ -3888,16 +3888,10 @@ A jump table for the options with a short description can be found at |Q_op|.
 	set a time.  This is to be compatible with Nvi.
 
 						*'maxcombine'* *'mco'*
-'maxcombine' 'mco'	number (default 2)
-			global
-			{only available when compiled with the |+multi_byte|
-			feature}
-	The maximum number of combining characters supported for displaying.
-	The default is OK for most languages.  Hebrew may require 4.
-	Maximum value is 6.
-	Even when this option is set to 2 you can still edit text with more
-	combining characters, you just can't see them.  Use |g8| or |ga|.
-	See |mbyte-combining|.
+'maxcombine' 'mco'	Removed. |vim-differences| {Nvim}
+	Nvim always displays up to 6 combining characters.  You can still edit
+    text with more than 6 combining characters, you just can't see them.
+    Use |g8| or |ga|.  See |mbyte-combining|.
 
 						*'maxfuncdepth'* *'mfd'*
 'maxfuncdepth' 'mfd'	number	(default 100)

runtime/doc/vim_diff.txt

@@ -409,6 +409,7 @@ Options:
   *'macatsui'*
   'maxmem' Nvim delegates memory-management to the OS.
   'maxmemtot' Nvim delegates memory-management to the OS.
+  'maxcombine' (6 is always used)
   *'restorescreen'* *'rs'* *'norestorescreen'* *'nors'*
   'shelltype'
   *'shortname'* *'sn'* *'noshortname'* *'nosn'*

src/nvim/option.c

@@ -4102,11 +4102,7 @@ static char *set_num_option(int opt_idx, char_u *varp, long value,
       errmsg = e_winwidth;
     }
   } else if (pp == &p_mco) {
-    if (value > MAX_MCO) {
-      errmsg = e_invarg;
-    } else if (value < 0) {
-      errmsg = e_positive;
-    }
+    value = MAX_MCO;
   } else if (pp == &p_titlelen) {
     if (value < 0) {
       errmsg = e_positive;
@@ -4268,8 +4264,6 @@ static char *set_num_option(int opt_idx, char_u *varp, long value,
     if (pp == &curbuf->b_p_sw || curbuf->b_p_sw == 0) {
       parse_cino(curbuf);
     }
-  } else if (pp == &p_mco) {
-    screenclear();          // will re-allocate the screen
   } else if (pp == &curbuf->b_p_iminsert) {
     showmode();
     // Show/unshow value of 'keymap' in status lines.

src/nvim/options.lua

@@ -1493,9 +1493,8 @@ return {
       full_name='maxcombine', abbreviation='mco',
       type='number', scope={'global'},
       vi_def=true,
-      redraw={'curswant'},
       varname='p_mco',
-      defaults={if_true={vi=2}}
+      defaults={if_true={vi=6}}
     },
     {
       full_name='maxfuncdepth', abbreviation='mfd',

test/functional/options/num_options_spec.lua

@@ -51,7 +51,6 @@ describe(':set validation', function()
     should_succeed('winminheight', 0)
     should_fail('winwidth', 0, 'E487')
     should_fail('helpheight', -1, 'E487')
-    should_fail('maxcombine', 7, 'E474')
     should_fail('iminsert', 3, 'E474')
     should_fail('imsearch', 3, 'E474')
     should_fail('titlelen', -1, 'E487')
@@ -94,4 +93,18 @@ describe(':set validation', function()
     feed_command('set winminwidth=3')
     eq('E592', eval("v:errmsg"):match("E%d*"))
   end)
+
+  it('set maxcombine resets to 6', function()
+    local function setto(value)
+      feed_command('setglobal maxcombine=' .. value)
+      feed_command('setlocal maxcombine=' .. value)
+      meths.set_option('maxcombine', value)
+      eq(6, meths.get_option('maxcombine'))
+      eq('', eval("v:errmsg"))
+    end
+    setto(0)
+    setto(1)
+    setto(6)
+    setto(7)
+  end)
 end)

test/functional/ui/fold_spec.lua

@@ -27,9 +27,8 @@ describe("folded lines", function()
   end)
 
   it("works with multibyte text", function()
-    -- Soon, we will always use the maximum value of 'maxcombine'.
-    feed_command("set maxcombine=6")
-
+    -- Currently the only allowed value of 'maxcombine'
+    eq(6, meths.get_option('maxcombine'))
     eq(true, meths.get_option('arabicshape'))
     insert([[
       å 语 x̨̣̘̫̲͚͎̎͂̀̂͛͛̾͢͟ العَرَبِيَّة