terminal: global 'scrollback' #6352

Make the 'scrollback' option work like most other buffer-local options:
- `:set scrollback=x` sets the global and local value
- `:setglobal scrollback=x` sets only the global default
- new terminal buffers inherit the global

Normal buffers are still always -1, and :setlocal there is an error.

Closes #6337

runtime/doc/options.txt

@@ -398,20 +398,6 @@ command, not when assigning a value to an option with ":let".
 Note the maximum length of an expanded option is limited.  How much depends on
 the system, mostly it is something like 256 or 1024 characters.
 
-							*Linux-backspace*
-			Note about Linux: By default the backspace key
-			produces CTRL-?, which is wrong.  You can fix it by
-			putting this line in your rc.local: >
-				echo "keycode 14 = BackSpace" | loadkeys
-<
-							*NetBSD-backspace*
-			Note about NetBSD: If your backspace doesn't produce
-			the right code, try this: >
-				xmodmap -e "keycode 22 = BackSpace"
-<			If this works, add this in your .Xmodmap file: >
-				keysym 22 = BackSpace
-<			You need to restart for this to take effect.
-
 ==============================================================================
 2. Automatically setting options			*auto-setting*
 

src/nvim/globals.h

@@ -1255,7 +1255,7 @@ typedef enum {
   kCdScopeInvalid = -1,
   kCdScopeWindow,  ///< Affects one window.
   kCdScopeTab,     ///< Affects one tab page.
-  kCdScopeGlobal,  ///< Affects the entire instance of Neovim.
+  kCdScopeGlobal,  ///< Affects the entire Nvim instance.
 } CdScope;
 
 #define MIN_CD_SCOPE  kCdScopeWindow

src/nvim/option.c

@@ -156,7 +156,6 @@ static long p_ts;
 static long p_tw;
 static int p_udf;
 static long p_wm;
-static long p_scbk;
 static char_u   *p_keymap;
 
 /* Saved values for when 'bin' is set. */
@@ -4199,16 +4198,13 @@ set_num_option (
     FOR_ALL_TAB_WINDOWS(tp, wp) {
       check_colorcolumn(wp);
     }
-  } else if (pp == &curbuf->b_p_scbk) {
+  } else if (pp == &curbuf->b_p_scbk || pp == &p_scbk) {
     // 'scrollback'
-    if (!curbuf->terminal) {
+    if (*pp < -1 || *pp > SB_MAX
+        || (opt_flags == OPT_LOCAL && !curbuf->terminal)) {
       errmsg = e_invarg;
-      curbuf->b_p_scbk = -1;
+      *pp = old_value;
-    } else {
+    } else if (curbuf->terminal) {
-      if (curbuf->b_p_scbk < -1 || curbuf->b_p_scbk > 100000) {
-        errmsg = e_invarg;
-        curbuf->b_p_scbk = 1000;
-      }
       // Force the scrollback to take effect.
       terminal_resize(curbuf->terminal, UINT16_MAX, UINT16_MAX);
     }
@@ -4331,6 +4327,11 @@ set_num_option (
   if ((opt_flags & (OPT_LOCAL | OPT_GLOBAL)) == 0)
     *(long *)get_varp_scope(&(options[opt_idx]), OPT_GLOBAL) = *pp;
 
+  if (pp == &curbuf->b_p_scbk && !curbuf->terminal) {
+    // Normal buffer: reset local 'scrollback' after updating the global value.
+    curbuf->b_p_scbk = -1;
+  }
+
   options[opt_idx].flags |= P_WAS_SET;
 
   if (!starting && errmsg == NULL) {
@@ -4586,7 +4587,7 @@ get_option_value (
 //
 // Pretends that option is absent if it is not present in the requested scope
 // (i.e. has no global, window-local or buffer-local value depending on
-// opt_type). Uses
+// opt_type).
 //
 // Returned flags:
 //       0 hidden or unknown option, also option that does not have requested 

src/nvim/option_defs.h

@@ -524,6 +524,7 @@ EXTERN int p_ru;                // 'ruler'
 EXTERN char_u   *p_ruf;         // 'rulerformat'
 EXTERN char_u   *p_pp;          // 'packpath'
 EXTERN char_u   *p_rtp;         // 'runtimepath'
+EXTERN long p_scbk;             // 'scrollback'
 EXTERN long p_sj;               // 'scrolljump'
 EXTERN long p_so;               // 'scrolloff'
 EXTERN char_u   *p_sbo;         // 'scrollopt'
@@ -811,4 +812,6 @@ enum {
 /* Value for b_p_ul indicating the global value must be used. */
 #define NO_LOCAL_UNDOLEVEL -123456
 
+#define SB_MAX 100000  // Maximum 'scrollback' value.
+
 #endif // NVIM_OPTION_DEFS_H

src/nvim/options.lua

@@ -1918,7 +1918,7 @@ return {
       vi_def=true,
       varname='p_scbk',
       redraw={'current_buffer'},
-      defaults={if_true={vi=-1}}
+      defaults={if_true={vi=1000}}
     },
     {
       full_name='scrollbind', abbreviation='scb',

src/nvim/terminal.c

@@ -85,8 +85,6 @@ typedef struct terminal_state {
 # include "terminal.c.generated.h"
 #endif
 
-#define SB_MAX 100000  // Maximum 'scrollback' value.
-
 // Delay for refreshing the terminal buffer after receiving updates from
 // libvterm. Improves performance when receiving large bursts of data.
 #define REFRESH_DELAY 10
@@ -233,7 +231,7 @@ Terminal *terminal_open(TerminalOptions opts)
   // Default settings for terminal buffers
   curbuf->b_p_ma = false;     // 'nomodifiable'
   curbuf->b_p_ul = -1;        // 'undolevels'
-  curbuf->b_p_scbk = 1000;  // 'scrollback'
+  curbuf->b_p_scbk = p_scbk;  // 'scrollback'
   curbuf->b_p_tw = 0;         // 'textwidth'
   set_option_value((uint8_t *)"wrap", false, NULL, OPT_LOCAL);
   set_option_value((uint8_t *)"number", false, NULL, OPT_LOCAL);
@@ -248,7 +246,8 @@ Terminal *terminal_open(TerminalOptions opts)
   apply_autocmds(EVENT_TERMOPEN, NULL, NULL, false, curbuf);
 
   // Configure the scrollback buffer.
-  rv->sb_size = curbuf->b_p_scbk < 0 ? SB_MAX : (size_t)curbuf->b_p_scbk;;
+  rv->sb_size = curbuf->b_p_scbk < 0
+                ? SB_MAX : (size_t)MAX(1, curbuf->b_p_scbk);
   rv->sb_buffer = xmalloc(sizeof(ScrollbackLine *) * rv->sb_size);
 
   if (!true_color) {

test/functional/terminal/scrollback_spec.lua

@@ -8,6 +8,7 @@ local command = helpers.command
 local wait = helpers.wait
 local retry = helpers.retry
 local curbufmeths = helpers.curbufmeths
+local nvim = helpers.nvim
 local feed_data = thelpers.feed_data
 
 if helpers.pending_win32(pending) then return end
@@ -368,6 +369,12 @@ describe("'scrollback' option", function()
     clear()
   end)
 
+  local function set_fake_shell()
+    -- shell-test.c is a fake shell that prints its arguments and exits.
+    nvim('set_option', 'shell', nvim_dir..'/shell-test')
+    nvim('set_option', 'shellcmdflag', 'EXE')
+  end
+
   local function expect_lines(expected, epsilon)
     local ep = epsilon and epsilon or 0
     local actual = eval("line('$')")
@@ -421,12 +428,13 @@ describe("'scrollback' option", function()
     screen:detach()
   end)
 
-  it('defaults to 1000', function()
+  it('defaults to 1000 in terminal buffers', function()
-    execute('terminal')
+    set_fake_shell()
+    command('terminal')
     eq(1000, curbufmeths.get_option('scrollback'))
   end)
 
-  it('error if set to invalid values', function()
+  it('error if set to invalid value', function()
     local status, rv = pcall(command, 'set scrollback=-2')
     eq(false, status)  -- assert failure
     eq('E474:', string.match(rv, "E%d*:"))
@@ -437,15 +445,32 @@ describe("'scrollback' option", function()
   end)
 
   it('defaults to -1 on normal buffers', function()
-    execute('new')
+    command('new')
     eq(-1, curbufmeths.get_option('scrollback'))
   end)
 
-  it('error if set on a normal buffer', function()
+  it(':setlocal in a normal buffer is an error', function()
     command('new')
-    execute('set scrollback=42')
+    execute('setlocal scrollback=42')
     feed('<CR>')
     eq('E474:', string.match(eval("v:errmsg"), "E%d*:"))
+    eq(-1, curbufmeths.get_option('scrollback'))
+  end)
+
+  it(':set updates local value and global default', function()
+    set_fake_shell()
+    command('set scrollback=42')                  -- set global and (attempt) local
+    eq(-1, curbufmeths.get_option('scrollback'))  -- normal buffer: -1
+    command('terminal')
+    eq(42, curbufmeths.get_option('scrollback'))  -- inherits global default
+    command('setlocal scrollback=99')
+    eq(99, curbufmeths.get_option('scrollback'))
+    command('set scrollback<')                    -- reset to global default
+    eq(42, curbufmeths.get_option('scrollback'))
+    command('setglobal scrollback=734')           -- new global default
+    eq(42, curbufmeths.get_option('scrollback'))  -- local value did not change
+    command('terminal')
+    eq(734, curbufmeths.get_option('scrollback'))
   end)
 
 end)