Add cursor trail color option

kitty/options/definition.py

@@ -416,6 +416,18 @@ animation.
 '''
     )
 
+opt('cursor_trail_color', 'none',
+    option_type='to_color_or_none',
+    ctype='!cursor_trail_color',
+    long_text='''
+Set the color of the cursor trail when :opt:`cursor_trail` is enabled.
+If set to 'none' (the default), the cursor trail will use the cursor's
+background color. Otherwise, specify a color value (e.g., #ff0000 for red,
+or a named color like 'red'). This allows you to customize the appearance
+of the cursor trail independently of the cursor color.
+'''
+)
+
 egr()  # }}}
 
 # scrollback {{{

kitty/options/parse.py

@@ -941,6 +941,9 @@ class Parser:
     def cursor_trail_decay(self, val: str, ans: dict[str, typing.Any]) -> None:
         ans['cursor_trail_decay'] = cursor_trail_decay(val)
 
+    def cursor_trail_color(self, val: str, ans: dict[str, typing.Any]) -> None:
+        ans['cursor_trail_color'] = to_color_or_none(val)
+
     def cursor_trail_start_threshold(self, val: str, ans: dict[str, typing.Any]) -> None:
         ans['cursor_trail_start_threshold'] = positive_int(val)
 

kitty/options/to-c-generated.h

@@ -226,6 +226,19 @@ convert_from_opts_cursor_trail_decay(PyObject *py_opts, Options *opts) {
     Py_DECREF(ret);
 }
 
+static void
+convert_from_python_cursor_trail_color(PyObject *val, Options *opts) {
+    cursor_trail_color(val, opts);
+}
+
+static void
+convert_from_opts_cursor_trail_color(PyObject *py_opts, Options *opts) {
+    PyObject *ret = PyObject_GetAttrString(py_opts, "cursor_trail_color");
+    if (ret == NULL) return;
+    convert_from_python_cursor_trail_color(ret, opts);
+    Py_DECREF(ret);
+}
+
 static void
 convert_from_python_cursor_trail_start_threshold(PyObject *val, Options *opts) {
     opts->cursor_trail_start_threshold = PyLong_AsLong(val);
@@ -1211,6 +1224,8 @@ convert_opts_from_python_opts(PyObject *py_opts, Options *opts) {
     if (PyErr_Occurred()) return false;
     convert_from_opts_cursor_trail_decay(py_opts, opts);
     if (PyErr_Occurred()) return false;
+    convert_from_opts_cursor_trail_color(py_opts, opts);
+    if (PyErr_Occurred()) return false;
     convert_from_opts_cursor_trail_start_threshold(py_opts, opts);
     if (PyErr_Occurred()) return false;
     convert_from_opts_scrollback_indicator_opacity(py_opts, opts);

kitty/options/to-c.h

@@ -215,6 +215,11 @@ cursor_trail_decay(PyObject *src, Options *opts) {
     opts->cursor_trail_decay_slow = PyFloat_AsFloat(PyTuple_GET_ITEM(src, 1));
 }
 
+static inline void
+cursor_trail_color(PyObject *src, Options *opts) {
+    opts->cursor_trail_color = color_or_none_as_int(src);
+}
+
 static void
 parse_font_mod_size(PyObject *val, float *sz, AdjustmentUnit *unit) {
     PyObject *mv = PyObject_GetAttrString(val, "mod_value");

kitty/options/types.py

@@ -337,6 +337,7 @@ option_names = (
     'cursor_text_color',
     'cursor_trail',
     'cursor_trail_decay',
+    'cursor_trail_color',
     'cursor_trail_start_threshold',
     'cursor_underline_thickness',
     'default_pointer_shape',
@@ -520,6 +521,7 @@ class Options:
     cursor_text_color: kitty.fast_data_types.Color | None = Color(17, 17, 17)
     cursor_trail: int = 0
     cursor_trail_decay: tuple[float, float] = (0.1, 0.4)
+    cursor_trail_color: kitty.fast_data_types.Color | None = None
     cursor_trail_start_threshold: int = 2
     cursor_underline_thickness: float = 2.0
     default_pointer_shape: choices_for_default_pointer_shape = 'beam'
@@ -1060,4 +1062,5 @@ nullable_colors = frozenset({
 })
 
 
-secret_options = ('remote_control_password', 'file_transfer_confirmation_bypass')
+secret_options = ('remote_control_password', 'file_transfer_confirmation_bypass')
+

kitty/options/utils.py

@@ -576,7 +576,6 @@ def cursor_trail_decay(x: str) -> tuple[float, float]:
     slow = max(slow, fast)
     return fast, slow
 
-
 def scrollback_lines(x: str) -> int:
     ans = int(x)
     if ans < 0:

kitty/shaders.c

@@ -1252,7 +1252,12 @@ draw_cursor_trail(CursorTrail *trail, Window *active_window) {
     glUniform2fv(trail_program_layout.uniforms.cursor_edge_x, 1, trail->cursor_edge_x);
     glUniform2fv(trail_program_layout.uniforms.cursor_edge_y, 1, trail->cursor_edge_y);
 
-    color_vec3(trail_program_layout.uniforms.trail_color, active_window ? active_window->render_data.screen->last_rendered.cursor_bg : OPT(foreground));
+    color_type trail_color = OPT(cursor_trail_color);
+    if (trail_color == 0) {  // 0 means "none" was specified
+        trail_color = active_window ? active_window->render_data.screen->last_rendered.cursor_bg : OPT(foreground);
+    }
+    color_vec3(trail_program_layout.uniforms.trail_color, trail_color);
+
     glUniform1fv(trail_program_layout.uniforms.trail_opacity, 1, &trail->opacity);
 
     glDrawArrays(GL_TRIANGLE_FAN, 0, 4);

kitty/state.h

@@ -54,6 +54,7 @@ typedef struct {
     monotonic_t cursor_trail;
     float cursor_trail_decay_fast;
     float cursor_trail_decay_slow;
+    color_type cursor_trail_color;
     float cursor_trail_start_threshold;
     unsigned int url_style;
     unsigned int scrollback_pager_history_size;