Merge #9509 'TUI: detect background color'

src/nvim/globals.h

@@ -83,10 +83,10 @@ EXTERN struct nvim_stats_s {
   int64_t redraw;
 } g_stats INIT(= { 0, 0 });
 
-/* Values for "starting" */
-#define NO_SCREEN       2       /* no screen updating yet */
-#define NO_BUFFERS      1       /* not all buffers loaded yet */
-/*                      0          not starting anymore */
+// Values for "starting".
+#define NO_SCREEN       2       // no screen updating yet
+#define NO_BUFFERS      1       // not all buffers loaded yet
+//                      0          not starting anymore
 
 /*
  * Number of Rows and Columns in the screen.

src/nvim/tui/input.c

@@ -7,8 +7,10 @@
 #include "nvim/api/vim.h"
 #include "nvim/api/private/helpers.h"
 #include "nvim/ascii.h"
+#include "nvim/charset.h"
 #include "nvim/main.h"
 #include "nvim/aucmd.h"
+#include "nvim/option.h"
 #include "nvim/os/os.h"
 #include "nvim/os/input.h"
 #include "nvim/event/rstream.h"
@@ -352,6 +354,85 @@ static bool handle_forced_escape(TermInput *input)
   return false;
 }
 
+static void set_bg_deferred(void **argv)
+{
+  char *bgvalue = argv[0];
+  if (starting) {
+    // Wait until after startup, so OptionSet is triggered.
+    loop_schedule(&main_loop, event_create(set_bg_deferred, 1, bgvalue));
+    return;
+  }
+  if (!option_was_set("bg") && !strequal((char *)p_bg, bgvalue)) {
+    // Value differs, apply it.
+    set_option_value("bg", 0L, bgvalue, 0);
+    reset_option_was_set("bg");
+  }
+}
+
+// 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` where R, G, and B 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.
+//
+// [1] https://en.wikipedia.org/wiki/Luma_%28video%29
+static bool handle_background_color(TermInput *input)
+{
+  size_t count = 0;
+  size_t component = 0;
+  uint16_t rgb[] = { 0, 0, 0 };
+  uint16_t rgb_max[] = { 0, 0, 0 };
+  bool eat_backslash = false;
+  bool done = false;
+  bool bad = false;
+  if (rbuffer_size(input->read_stream.buffer) >= 9
+      && !rbuffer_cmp(input->read_stream.buffer, "\x1b]11;rgb:", 9)) {
+    rbuffer_consumed(input->read_stream.buffer, 9);
+    RBUFFER_EACH(input->read_stream.buffer, c, i) {
+      count = i + 1;
+      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 == '/') {
+        if (component < 3) {
+          component++;
+        }
+      } 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;
+      }
+    }
+    rbuffer_consumed(input->read_stream.buffer, count);
+    if (done && !bad && rgb_max[0] && rgb_max[1] && rgb_max[2]) {
+      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
+      char *bgvalue = luminance < 0.5 ? "dark" : "light";
+      DLOG("bg response: %s", bgvalue);
+      loop_schedule(&main_loop, event_create(set_bg_deferred, 1, bgvalue));
+    } else {
+      DLOG("failed to parse bg response");
+    }
+    return true;
+  }
+  return false;
+}
+
 static void read_cb(Stream *stream, RBuffer *buf, size_t count_, void *data,
                     bool eof)
 {
@@ -381,7 +462,8 @@ static void read_cb(Stream *stream, RBuffer *buf, size_t count_, void *data,
   do {
     if (handle_focus_event(input)
         || handle_bracketed_paste(input)
-        || handle_forced_escape(input)) {
+        || handle_forced_escape(input)
+        || handle_background_color(input)) {
       continue;
     }
 

src/nvim/tui/tui.c

@@ -123,6 +123,7 @@ typedef struct {
     int set_cursor_style, reset_cursor_style;
     int save_title, restore_title;
     int enter_undercurl_mode, exit_undercurl_mode, set_underline_color;
+    int get_bg;
   } unibi_ext;
   char *space_buf;
 } TUIData;
@@ -211,6 +212,7 @@ static void terminfo_start(UI *ui)
   data->unibi_ext.reset_scroll_region = -1;
   data->unibi_ext.set_cursor_style = -1;
   data->unibi_ext.reset_cursor_style = -1;
+  data->unibi_ext.get_bg = -1;
   data->out_fd = 1;
   data->out_isatty = os_isatty(data->out_fd);
 
@@ -281,6 +283,8 @@ static void terminfo_start(UI *ui)
   unibi_out_ext(ui, data->unibi_ext.save_title);
   unibi_out(ui, unibi_keypad_xmit);
   unibi_out(ui, unibi_clear_screen);
+  // Ask the terminal to send us the background color.
+  unibi_out_ext(ui, data->unibi_ext.get_bg);
   // Enable bracketed paste
   unibi_out_ext(ui, data->unibi_ext.enable_bracketed_paste);
 
@@ -1648,6 +1652,9 @@ static void patch_terminfo_bugs(TUIData *data, const char *term,
 #define XTERM_SETAB_16 \
   "\x1b[%?%p1%{8}%<%t4%p1%d%e%p1%{16}%<%t10%p1%{8}%-%d%e39%;m"
 
+  data->unibi_ext.get_bg = (int)unibi_add_ext_str(ut, "ext.get_bg",
+                                                  "\x1b]11;?\x07");
+
   // Terminals with 256-colour SGR support despite what terminfo says.
   if (unibi_get_num(ut, unibi_max_colors) < 256) {
     // See http://fedoraproject.org/wiki/Features/256_Color_Terminals