Allow specifying text formatting in tab_title_template

Fixes #3146

Author: kovidgoyal

docs/changelog.rst

@@ -13,6 +13,8 @@ To update |kitty|, :doc:`follow the instructions <binary>`.
 - Add a new mappable `select_tab` action to choose a tab to switch to even
   when the tab bar is hidden (:iss:`3115`)
 
+- Allow specifying text formatting in :opt:`tab_title_template` (:iss:`3146`)
+
 - Graphics protocol: Add support for giving individual image placements their
   own ids. This is a backwards compatible protocol extension, and also allow
   suppressing responses from the terminal to commands (:iss:`3133`)

kitty/config_data.py

@@ -939,6 +939,10 @@ def active_tab_title_template(x: str) -> Optional[str]:
 in the tab. Note that formatting is done by Python's string formatting
 machinery, so you can use, for instance, :code:`{layout_name[:2].upper()}` to
 show only the first two letters of the layout name, upper-cased.
+If you want to style the text, you can use styling directives, for example:
+:code:`{fmt.fg.red}red{fmt.fg.default}normal{fmt.bg._00FF00}green bg{fmt.bg.normal}`.
+Similarly, for bold and italic:
+:code:`{fmt.bold}bold{fmt.nobold}normal{fmt.italic}italic{fmt.noitalic}`.
 '''))
 o('active_tab_title_template', 'none', option_type=active_tab_title_template, long_text=_('''
 Template to use for active tabs, if not specified falls back

kitty/fast_data_types.pyi

@@ -1002,6 +1002,9 @@ class Screen:
     def draw(self, text: str) -> None:
         pass
 
+    def apply_sgr(self, text: str) -> None:
+        pass
+
     def copy_colors_from(self, other: 'Screen') -> None:
         pass
 

kitty/parser.c

@@ -52,7 +52,6 @@ utf8(char_type codepoint) {
 // }}}
 
 // Macros {{{
-#define MAX_PARAMS 256
 #define IS_DIGIT \
     case '0': \
     case '1': \
@@ -465,7 +464,10 @@ repr_csi_params(unsigned int *params, unsigned int num_params) {
     return buf;
 }
 
-static inline void
+#ifdef DUMP_COMMANDS
+static
+#endif
+void
 parse_sgr(Screen *screen, uint32_t *buf, unsigned int num, unsigned int *params, PyObject DUMP_UNUSED *dump_callback, const char *report_name DUMP_UNUSED, Region *region) {
     enum State { START, NORMAL, MULTIPLE, COLOR, COLOR1, COLOR3 };
     enum State state = START;

kitty/screen.c

@@ -2137,6 +2137,20 @@ draw(Screen *self, PyObject *src) {
     Py_RETURN_NONE;
 }
 
+extern void
+parse_sgr(Screen *screen, uint32_t *buf, unsigned int num, unsigned int *params, PyObject *dump_callback, const char *report_name, Region *region);
+
+static PyObject*
+apply_sgr(Screen *self, PyObject *src) {
+    if (!PyUnicode_Check(src)) { PyErr_SetString(PyExc_TypeError, "A unicode string is required"); return NULL; }
+    if (PyUnicode_READY(src) != 0) { return PyErr_NoMemory(); }
+    Py_UCS4 *buf = PyUnicode_AsUCS4Copy(src);
+    if (!buf) return NULL;
+    unsigned int params[MAX_PARAMS] = {0};
+    parse_sgr(self, buf, PyUnicode_GET_LENGTH(src), params, NULL, "parse_sgr", NULL);
+    Py_RETURN_NONE;
+}
+
 static PyObject*
 reset_mode(Screen *self, PyObject *args) {
     int private = false;
@@ -2783,6 +2797,7 @@ static PyMethodDef methods[] = {
     MND(visual_line, METH_VARARGS)
     MND(current_url_text, METH_NOARGS)
     MND(draw, METH_O)
+    MND(apply_sgr, METH_O)
     MND(cursor_position, METH_VARARGS)
     MND(set_mode, METH_VARARGS)
     MND(reset_mode, METH_VARARGS)

kitty/screen.h

@@ -8,6 +8,7 @@
 
 #include "graphics.h"
 #include "monotonic.h"
+#define MAX_PARAMS 256
 
 typedef enum ScrollTypes { SCROLL_LINE = -999999, SCROLL_PAGE, SCROLL_FULL } ScrollType;
 

kitty/tab_bar.py

@@ -13,7 +13,7 @@
 )
 from .layout.base import Rect
 from .options_stub import Options
-from .rgb import Color, alpha_blend, color_from_int
+from .rgb import Color, alpha_blend, color_as_sgr, color_from_int, to_color
 from .utils import color_as_int, log_error
 from .window import calculate_gl_geometry
 
@@ -61,6 +61,35 @@ def compile_template(template: str) -> Any:
         report_template_failure(template, str(e))
 
 
+class ColorFormatter:
+
+    def __init__(self, which: str):
+        self.which = which
+
+    def __getattr__(self, name: str) -> str:
+        q = name
+        if q == 'default':
+            ans = '9'
+        else:
+            if name.startswith('_'):
+                q = '#' + name[1:]
+            c = to_color(q)
+            if c is None:
+                raise AttributeError(f'{name} is not a valid color')
+            ans = '8' + color_as_sgr(c)
+        return f'\x1b[{self.which}{ans}m'
+
+
+class Formatter:
+    reset = '\x1b[0m'
+    fg = ColorFormatter('3')
+    bg = ColorFormatter('4')
+    bold = '\x1b[1m'
+    nobold = '\x1b[22m'
+    italic = '\x1b[3m'
+    noitalic = '\x1b[23m'
+
+
 def draw_title(draw_data: DrawData, screen: Screen, tab: TabBarData, index: int) -> None:
     if tab.needs_attention and draw_data.bell_on_tab:
         fg = screen.cursor.fg
@@ -81,13 +110,22 @@ def draw_title(draw_data: DrawData, screen: Screen, tab: TabBarData, index: int)
             'index': index,
             'layout_name': tab.layout_name,
             'num_windows': tab.num_windows,
-            'title': tab.title
+            'title': tab.title,
+            'fmt': Formatter,
         }
         title = eval(compile_template(template), {'__builtins__': {}}, eval_locals)
     except Exception as e:
         report_template_failure(template, str(e))
         title = tab.title
-    screen.draw(title)
+    if '\x1b' in title:
+        import re
+        for x in re.split('(\x1b\\[[^m]*m)', title):
+            if x.startswith('\x1b') and x.endswith('m'):
+                screen.apply_sgr(x[2:-1])
+            else:
+                screen.draw(x)
+    else:
+        screen.draw(title)
 
 
 def draw_tab_with_separator(draw_data: DrawData, screen: Screen, tab: TabBarData, before: int, max_title_length: int, index: int, is_last: bool) -> int: