refactor: move background color detection into Lua

7 files changed, 133 insertions, 309 deletions

diff --git a/runtime/lua/vim/_defaults.lua b/runtime/lua/vim/_defaults.lua
index c1b50e6950..0d7b4f1884 100644
--- a/runtime/lua/vim/_defaults.lua
+++ b/runtime/lua/vim/_defaults.lua
@@ -164,3 +164,133 @@ do
     end,
   })
 end
+
+--- Guess value of 'background' based on terminal color.
+---
+--- We write Operating System Command (OSC) 11 to the terminal to request the
+--- terminal's background color. We then wait for a response. If the response
+--- matches `rgba:RRRR/GGGG/BBBB/AAAA` where R, G, B, and A are hex digits, then
+--- compute the luminance[1] of the RGB color and classify it as light/dark
+--- accordingly. Note that the color components may have anywhere from one to
+--- four hex digits, and require scaling accordingly as values out of 4, 8, 12,
+--- or 16 bits. Also note the A(lpha) component is optional, and is parsed but
+--- ignored in the calculations.
+---
+--- [1] https://en.wikipedia.org/wiki/Luma_%28video%29
+do
+  --- Parse a string of hex characters as a color.
+  ---
+  --- The string can contain 1 to 4 hex characters. The returned value is
+  --- between 0.0 and 1.0 (inclusive) representing the intensity of the color.
+  ---
+  --- For instance, if only a single hex char "a" is used, then this function
+  --- returns 0.625 (10 / 16), while a value of "aa" would return 0.664 (170 /
+  --- 256).
+  ---
+  --- @param c string Color as a string of hex chars
+  --- @return number? Intensity of the color
+  local function parsecolor(c)
+    local len = #c
+    assert(len > 0 and len <= 4, 'Invalid hex color string')
+    if not c:match('^0x') then
+      c = string.format('0x%s', c)
+    end
+
+    local max = tonumber(string.format('0x%s', string.rep('f', len)))
+    return tonumber(c) / max
+  end
+
+  --- Parse an OSC 11 response
+  ---
+  --- Either of the two formats below are accepted:
+  ---
+  ---   OSC 11 ; rgb:<red>/<green>/<blue>
+  ---
+  --- or
+  ---
+  ---   OSC 11 ; rgba:<red>/<green>/<blue>/<alpha>
+  ---
+  --- where
+  ---
+  ---   <red>, <green>, <blue>, <alpha> := h | hh | hhh | hhhh
+  ---
+  --- The alpha component is ignored, if present.
+  ---
+  --- @param resp string OSC 11 response
+  --- @return string? Red component
+  --- @return string? Green component
+  --- @return string? Blue component
+  local function parseosc11(resp)
+    local r, g, b
+    r, g, b = resp:match('^\027%]11;rgb:(%x+)/(%x+)/(%x+)$')
+    if not r and not g and not b then
+      local a
+      r, g, b, a = resp:match('^\027%]11;rgba:(%x+)/(%x+)/(%x+)/(%x+)$')
+      if not a or #a > 4 then
+        return nil, nil, nil
+      end
+    end
+
+    if r and g and b and #r <= 4 and #g <= 4 and #b <= 4 then
+      return r, g, b
+    end
+
+    return nil, nil, nil
+  end
+
+  local tty = false
+  for _, ui in ipairs(vim.api.nvim_list_uis()) do
+    if ui.chan == 1 and ui.stdout_tty then
+      tty = true
+      break
+    end
+  end
+
+  if tty then
+    local timer = assert(vim.uv.new_timer())
+
+    local id = vim.api.nvim_create_autocmd('TermResponse', {
+      nested = true,
+      callback = function(args)
+        if vim.api.nvim_get_option_info2('background', {}).was_set then
+          -- Don't do anything if 'background' is already set
+          timer:stop()
+          timer:close()
+          return true
+        end
+
+        local resp = args.data ---@type string
+        local r, g, b = parseosc11(resp)
+        if r and g and b then
+          local rr = parsecolor(r)
+          local gg = parsecolor(g)
+          local bb = parsecolor(b)
+
+          if rr and gg and bb then
+            local luminance = (0.299 * rr) + (0.587 * gg) + (0.114 * bb)
+            local bg = luminance < 0.5 and 'dark' or 'light'
+            if bg ~= vim.o.background then
+              vim.o.background = bg
+            end
+          end
+
+          timer:stop()
+          timer:close()
+
+          return true
+        end
+      end,
+    })
+
+    io.stdout:write('\027]11;?\027\\')
+
+    timer:start(1000, 0, function()
+      -- No response received. Delete the autocommand
+      vim.schedule(function()
+        -- Suppress error if autocommand has already been deleted
+        pcall(vim.api.nvim_del_autocmd, id)
+      end)
+      timer:close()
+    end)
+  end
+end
diff --git a/src/nvim/api/ui.c b/src/nvim/api/ui.c
index 3d013435f7..a215317a83 100644
--- a/src/nvim/api/ui.c
+++ b/src/nvim/api/ui.c
@@ -348,15 +348,6 @@ static void ui_set_option(UI *ui, bool init, String name, Object value, Error *e
     return;
   }
 
-  if (strequal(name.data, "term_background")) {
-    VALIDATE_T("term_background", kObjectTypeString, value.type, {
-      return;
-    });
-    set_tty_background(value.data.string.data);
-    ui->term_background = string_to_cstr(value.data.string);
-    return;
-  }
-
   if (strequal(name.data, "stdin_fd")) {
     VALIDATE_T("stdin_fd", kObjectTypeInteger, value.type, {
       return;
diff --git a/src/nvim/option.c b/src/nvim/option.c
index 23d5960579..d3a8e2ce73 100644
--- a/src/nvim/option.c
+++ b/src/nvim/option.c
@@ -3183,23 +3183,6 @@ bool set_tty_option(const char *name, char *value)
   return false;
 }
 
-void set_tty_background(const char *value)
-{
-  if (option_was_set("bg") || strequal(p_bg, value)) {
-    // background is already set... ignore
-    return;
-  }
-  if (starting) {
-    // Wait until after startup, so OptionSet is triggered.
-    do_cmdline_cmd((value[0] == 'l')
-                   ? "autocmd VimEnter * ++once ++nested :lua if not vim.api.nvim_get_option_info2('bg', {}).was_set then vim.o.bg = 'light' end"
-                   : "autocmd VimEnter * ++once ++nested :lua if not vim.api.nvim_get_option_info2('bg', {}).was_set then vim.o.bg = 'dark' end");
-  } else {
-    set_option_value_give_err("bg", CSTR_AS_OPTVAL((char *)value), 0);
-    reset_option_was_set("bg");
-  }
-}
-
 /// Find index for an option
 ///
 /// @param[in]  arg  Option name.
diff --git a/src/nvim/tui/input.c b/src/nvim/tui/input.c
index 36d6566c7d..7dce8473d5 100644
--- a/src/nvim/tui/input.c
+++ b/src/nvim/tui/input.c
@@ -124,7 +124,6 @@ void tinput_init(TermInput *input, Loop *loop)
   input->loop = loop;
   input->paste = 0;
   input->in_fd = STDIN_FILENO;
-  input->waiting_for_bg_response = 0;
   input->extkeys_type = kExtkeysNone;
   input->ttimeout = (bool)p_ttimeout;
   input->ttimeoutlen = p_ttm;
@@ -579,113 +578,6 @@ static HandleState handle_bracketed_paste(TermInput *input)
   return kNotApplicable;
 }
 
-static void set_bg(char *bgvalue)
-{
-  if (ui_client_attached) {
-    MAXSIZE_TEMP_ARRAY(args, 2);
-    ADD_C(args, CSTR_AS_OBJ("term_background"));
-    ADD_C(args, CSTR_AS_OBJ(bgvalue));
-    rpc_send_event(ui_client_channel_id, "nvim_ui_set_option", args);
-  }
-}
-
-// During startup, tui.c requests the background color (see `ext.get_bg`).
-//
-// Here in input.c, we watch for the terminal response `\e]11;COLOR\a`.  If
-// COLOR matches `rgb:RRRR/GGGG/BBBB/AAAA` where R, G, B, and A are hex digits,
-// then compute the luminance[1] of the RGB color and classify it as light/dark
-// accordingly. Note that the color components may have anywhere from one to
-// four hex digits, and require scaling accordingly as values out of 4, 8, 12,
-// or 16 bits. Also note the A(lpha) component is optional, and is parsed but
-// ignored in the calculations.
-//
-// [1] https://en.wikipedia.org/wiki/Luma_%28video%29
-HandleState handle_background_color(TermInput *input)
-{
-  if (input->waiting_for_bg_response <= 0) {
-    return kNotApplicable;
-  }
-  size_t count = 0;
-  size_t component = 0;
-  size_t header_size = 0;
-  size_t num_components = 0;
-  size_t buf_size = rbuffer_size(input->read_stream.buffer);
-  uint16_t rgb[] = { 0, 0, 0 };
-  uint16_t rgb_max[] = { 0, 0, 0 };
-  bool eat_backslash = false;
-  bool done = false;
-  bool bad = false;
-  if (buf_size >= 9
-      && !rbuffer_cmp(input->read_stream.buffer, "\x1b]11;rgb:", 9)) {
-    header_size = 9;
-    num_components = 3;
-  } else if (buf_size >= 10
-             && !rbuffer_cmp(input->read_stream.buffer, "\x1b]11;rgba:", 10)) {
-    header_size = 10;
-    num_components = 4;
-  } else if (buf_size < 10
-             && !rbuffer_cmp(input->read_stream.buffer,
-                             "\x1b]11;rgba", buf_size)) {
-    // An incomplete sequence was found, waiting for the next input.
-    return kIncomplete;
-  } else {
-    input->waiting_for_bg_response--;
-    if (input->waiting_for_bg_response == 0) {
-      DLOG("did not get a response for terminal background query");
-    }
-    return kNotApplicable;
-  }
-  RBUFFER_EACH(input->read_stream.buffer, c, i) {
-    count = i + 1;
-    // Skip the header.
-    if (i < header_size) {
-      continue;
-    }
-    if (eat_backslash) {
-      done = true;
-      break;
-    } else if (c == '\x07') {
-      done = true;
-      break;
-    } else if (c == '\x1b') {
-      eat_backslash = true;
-    } else if (bad) {
-      // ignore
-    } else if ((c == '/') && (++component < num_components)) {
-      // work done in condition
-    } else if (ascii_isxdigit(c)) {
-      if (component < 3 && rgb_max[component] != 0xffff) {
-        rgb_max[component] = (uint16_t)((rgb_max[component] << 4) | 0xf);
-        rgb[component] = (uint16_t)((rgb[component] << 4) | hex2nr(c));
-      }
-    } else {
-      bad = true;
-    }
-  }
-  if (done && !bad && rgb_max[0] && rgb_max[1] && rgb_max[2]) {
-    rbuffer_consumed(input->read_stream.buffer, count);
-    double r = (double)rgb[0] / (double)rgb_max[0];
-    double g = (double)rgb[1] / (double)rgb_max[1];
-    double b = (double)rgb[2] / (double)rgb_max[2];
-    double luminance = (0.299 * r) + (0.587 * g) + (0.114 * b);  // CCIR 601
-    bool is_dark = luminance < 0.5;
-    char *bgvalue = is_dark ? "dark" : "light";
-    DLOG("bg response: %s", bgvalue);
-    ui_client_bg_response = is_dark ? kTrue : kFalse;
-    set_bg(bgvalue);
-    input->waiting_for_bg_response = 0;
-  } else if (!done && !bad) {
-    // An incomplete sequence was found, waiting for the next input.
-    return kIncomplete;
-  } else {
-    input->waiting_for_bg_response = 0;
-    rbuffer_consumed(input->read_stream.buffer, count);
-    DLOG("failed to parse bg response");
-    return kNotApplicable;
-  }
-  return kComplete;
-}
-
 static void handle_osc_event(TermInput *input, const TermKeyKey *key)
 {
   assert(input);
@@ -712,14 +604,12 @@ static void handle_osc_event(TermInput *input, const TermKeyKey *key)
 static void handle_raw_buffer(TermInput *input, bool force)
 {
   HandleState is_paste = kNotApplicable;
-  HandleState is_bc = kNotApplicable;
 
   do {
     if (!force
         && (handle_focus_event(input)
-            || (is_paste = handle_bracketed_paste(input)) != kNotApplicable
-            || (is_bc = handle_background_color(input)) != kNotApplicable)) {
-      if (is_paste == kIncomplete || is_bc == kIncomplete) {
+            || (is_paste = handle_bracketed_paste(input)) != kNotApplicable)) {
+      if (is_paste == kIncomplete) {
         // Wait for the next input, leaving it in the raw buffer due to an
         // incomplete sequence.
         return;
diff --git a/src/nvim/tui/input.h b/src/nvim/tui/input.h
index 8b4d1ba74b..01514269be 100644
--- a/src/nvim/tui/input.h
+++ b/src/nvim/tui/input.h
@@ -24,7 +24,6 @@ typedef struct term_input {
   // Phases: -1=all 0=disabled 1=first-chunk 2=continue 3=last-chunk
   int8_t paste;
   bool ttimeout;
-  int8_t waiting_for_bg_response;
   int8_t waiting_for_csiu_response;
   ExtkeysType extkeys_type;
   OptInt ttimeoutlen;
diff --git a/src/nvim/tui/tui.c b/src/nvim/tui/tui.c
index 177ef0c3cf..8aab4d836c 100644
--- a/src/nvim/tui/tui.c
+++ b/src/nvim/tui/tui.c
@@ -133,7 +133,6 @@ struct TUIData {
     int reset_scroll_region;
     int set_cursor_style, reset_cursor_style;
     int save_title, restore_title;
-    int get_bg;
     int set_underline_style;
     int set_underline_color;
     int enable_extended_keys, disable_extended_keys;
@@ -250,7 +249,6 @@ static void terminfo_start(TUIData *tui)
   tui->unibi_ext.reset_scroll_region = -1;
   tui->unibi_ext.set_cursor_style = -1;
   tui->unibi_ext.reset_cursor_style = -1;
-  tui->unibi_ext.get_bg = -1;
   tui->unibi_ext.set_underline_color = -1;
   tui->unibi_ext.enable_extended_keys = -1;
   tui->unibi_ext.disable_extended_keys = -1;
@@ -327,9 +325,7 @@ static void terminfo_start(TUIData *tui)
   unibi_out(tui, unibi_enter_ca_mode);
   unibi_out(tui, unibi_keypad_xmit);
   unibi_out(tui, unibi_clear_screen);
-  // Ask the terminal to send us the background color.
-  tui->input.waiting_for_bg_response = 5;
-  unibi_out_ext(tui, tui->unibi_ext.get_bg);
+
   // Enable bracketed paste
   unibi_out_ext(tui, tui->unibi_ext.enable_bracketed_paste);
 
@@ -1882,9 +1878,6 @@ static void patch_terminfo_bugs(TUIData *tui, const char *term, const char *colo
 #define XTERM_SETAB_16 \
   "\x1b[%?%p1%{8}%<%t4%p1%d%e%p1%{16}%<%t10%p1%{8}%-%d%e39%;m"
 
-  tui->unibi_ext.get_bg = (int)unibi_add_ext_str(ut, "ext.get_bg",
-                                                 "\x1b]11;?\x07");
-
   // Query the terminal to see if it supports CSI u key encoding by writing CSI
   // ? u followed by a request for the primary device attributes (CSI c)
   // See https://sw.kovidgoyal.net/kitty/keyboard-protocol/#detection-of-support-for-this-protocol
diff --git a/test/unit/tui_spec.lua b/test/unit/tui_spec.lua
deleted file mode 100644
index 192e35a485..0000000000
--- a/test/unit/tui_spec.lua
+++ /dev/null
@@ -1,162 +0,0 @@
-local helpers = require("test.unit.helpers")(after_each)
-local cimport = helpers.cimport
-local eq = helpers.eq
-local ffi = helpers.ffi
-local itp = helpers.gen_itp(it)
-local to_cstr = helpers.to_cstr
-
-local cinput = cimport("./src/nvim/tui/input.h")
-local rbuffer = cimport("./test/unit/fixtures/rbuffer.h")
-local globals = cimport("./src/nvim/globals.h")
-local multiqueue = cimport("./test/unit/fixtures/multiqueue.h")
-local ui_client = cimport("./src/nvim/ui_client.h")
-
-itp('handle_background_color', function()
-  local handle_background_color = cinput.handle_background_color
-  local term_input = ffi.new('TermInput', {})
-  local events = globals.main_loop.thread_events
-  local kIncomplete = cinput.kIncomplete
-  local kNotApplicable = cinput.kNotApplicable
-  local kComplete = cinput.kComplete
-
-  -- Short-circuit when not waiting for response.
-  term_input.waiting_for_bg_response = 0
-  eq(kNotApplicable, handle_background_color(term_input))
-
-  local capacity = 100
-  local rbuf = ffi.gc(rbuffer.rbuffer_new(capacity), rbuffer.rbuffer_free)
-  term_input.read_stream.buffer = rbuf
-
-  local function assert_bg(colorspace, color, bg)
-    local term_response = '\027]11;'..colorspace..':'..color..'\007'
-    rbuffer.rbuffer_write(rbuf, to_cstr(term_response), #term_response)
-
-    term_input.waiting_for_bg_response = 1
-    eq(kComplete, handle_background_color(term_input))
-    eq(0, term_input.waiting_for_bg_response)
-    eq(0, multiqueue.multiqueue_size(events))
-    eq(bg, ({[0]="light", [1] = "dark", [-1] = "none"})
-           [tonumber(ui_client.ui_client_bg_response)])
-
-    -- Buffer has been consumed.
-    eq(0, rbuf.size)
-  end
-
-  assert_bg('rgb', '0000/0000/0000', 'dark')
-  assert_bg('rgb', 'ffff/ffff/ffff', 'light')
-  assert_bg('rgb', '000/000/000', 'dark')
-  assert_bg('rgb', 'fff/fff/fff', 'light')
-  assert_bg('rgb', '00/00/00', 'dark')
-  assert_bg('rgb', 'ff/ff/ff', 'light')
-  assert_bg('rgb', '0/0/0', 'dark')
-  assert_bg('rgb', 'f/f/f', 'light')
-
-  assert_bg('rgb', 'f/0/0', 'dark')
-  assert_bg('rgb', '0/f/0', 'light')
-  assert_bg('rgb', '0/0/f', 'dark')
-
-  assert_bg('rgb', '1/1/1', 'dark')
-  assert_bg('rgb', '2/2/2', 'dark')
-  assert_bg('rgb', '3/3/3', 'dark')
-  assert_bg('rgb', '4/4/4', 'dark')
-  assert_bg('rgb', '5/5/5', 'dark')
-  assert_bg('rgb', '6/6/6', 'dark')
-  assert_bg('rgb', '7/7/7', 'dark')
-  assert_bg('rgb', '8/8/8', 'light')
-  assert_bg('rgb', '9/9/9', 'light')
-  assert_bg('rgb', 'a/a/a', 'light')
-  assert_bg('rgb', 'b/b/b', 'light')
-  assert_bg('rgb', 'c/c/c', 'light')
-  assert_bg('rgb', 'd/d/d', 'light')
-  assert_bg('rgb', 'e/e/e', 'light')
-
-  assert_bg('rgb', '0/e/0', 'light')
-  assert_bg('rgb', '0/d/0', 'light')
-  assert_bg('rgb', '0/c/0', 'dark')
-  assert_bg('rgb', '0/b/0', 'dark')
-
-  assert_bg('rgb', 'f/0/f', 'dark')
-  assert_bg('rgb', 'f/1/f', 'dark')
-  assert_bg('rgb', 'f/2/f', 'dark')
-  assert_bg('rgb', 'f/3/f', 'light')
-  assert_bg('rgb', 'f/4/f', 'light')
-
-  assert_bg('rgba', '0000/0000/0000/0000', 'dark')
-  assert_bg('rgba', '0000/0000/0000/ffff', 'dark')
-  assert_bg('rgba', 'ffff/ffff/ffff/0000', 'light')
-  assert_bg('rgba', 'ffff/ffff/ffff/ffff', 'light')
-  assert_bg('rgba', '000/000/000/000', 'dark')
-  assert_bg('rgba', '000/000/000/fff', 'dark')
-  assert_bg('rgba', 'fff/fff/fff/000', 'light')
-  assert_bg('rgba', 'fff/fff/fff/fff', 'light')
-  assert_bg('rgba', '00/00/00/00', 'dark')
-  assert_bg('rgba', '00/00/00/ff', 'dark')
-  assert_bg('rgba', 'ff/ff/ff/00', 'light')
-  assert_bg('rgba', 'ff/ff/ff/ff', 'light')
-  assert_bg('rgba', '0/0/0/0', 'dark')
-  assert_bg('rgba', '0/0/0/f', 'dark')
-  assert_bg('rgba', 'f/f/f/0', 'light')
-  assert_bg('rgba', 'f/f/f/f', 'light')
-
-
-  -- Incomplete sequence: necessarily correct behavior.
-  local term_response = '\027]11;rgba:f/f/f/f'  -- missing '\007
-  rbuffer.rbuffer_write(rbuf, to_cstr(term_response), #term_response)
-
-  term_input.waiting_for_bg_response = 1
-  eq(kIncomplete, handle_background_color(term_input))
-  eq(1, term_input.waiting_for_bg_response)
-  eq(#term_response, rbuf.size)
-
-  term_response = '\007'
-  rbuffer.rbuffer_write(rbuf, to_cstr(term_response), #term_response)
-  eq(kComplete, handle_background_color(term_input))
-  eq(0, term_input.waiting_for_bg_response)
-
-  eq(0, tonumber(ui_client.ui_client_bg_response))
-  eq(0, multiqueue.multiqueue_size(events))
-  eq(0, rbuf.size)
-
-  term_response = '\027]11;rg'
-  rbuffer.rbuffer_write(rbuf, to_cstr(term_response), #term_response)
-
-  term_input.waiting_for_bg_response = 1
-  eq(kIncomplete, handle_background_color(term_input))
-  eq(1, term_input.waiting_for_bg_response)
-  eq(#term_response, rbuf.size)
-
-  term_response = 'ba:f/f/f/f\007'
-  rbuffer.rbuffer_write(rbuf, to_cstr(term_response), #term_response)
-  eq(kComplete, handle_background_color(term_input))
-  eq(0, term_input.waiting_for_bg_response)
-
-  eq(0, tonumber(ui_client.ui_client_bg_response))
-  eq(0, multiqueue.multiqueue_size(events))
-  eq(0, rbuf.size)
-
-
-  -- Does nothing when not at start of buffer.
-  term_response = '123\027]11;rgba:f/f/f/f\007456'
-  rbuffer.rbuffer_write(rbuf, to_cstr(term_response), #term_response)
-
-  term_input.waiting_for_bg_response = 3
-  eq(kNotApplicable, handle_background_color(term_input))
-  eq(2, term_input.waiting_for_bg_response)
-
-  eq(0, multiqueue.multiqueue_size(events))
-  eq(#term_response, rbuf.size)
-  rbuffer.rbuffer_consumed(rbuf, #term_response)
-
-
-  -- Keeps trailing buffer.
-  term_response = '\027]11;rgba:f/f/f/f\007456'
-  rbuffer.rbuffer_write(rbuf, to_cstr(term_response), #term_response)
-
-  term_input.waiting_for_bg_response = 1
-  eq(kComplete, handle_background_color(term_input))
-  eq(0, term_input.waiting_for_bg_response)
-
-  eq(0, multiqueue.multiqueue_size(events))
-  eq(3, rbuf.size)
-  rbuffer.rbuffer_consumed(rbuf, rbuf.size)
-end)