Add wheel_scroll_min_lines to set the minimum scrolling lines

kitty/mouse.c

@@ -888,9 +888,13 @@ scroll_event(double UNUSED xoffset, double yoffset, int flags, int modifiers) {
     } else {
         SCALE_SCROLL(wheel_scroll_multiplier);
         s = (int) round(yoffset);
+        int min_lines = OPT(wheel_scroll_min_lines);
+        if (min_lines > 0 && abs(s) < min_lines) s = yoffset > 0 ? min_lines : -min_lines;
+        // Add the minimum number of lines when it is negative and the scrolling acceleration takes effect
+        else if (min_lines < 0) s = yoffset > 0 ? s - min_lines : s + min_lines;
         // apparently on cocoa some mice generate really small yoffset values
         // when scrolling slowly https://github.com/kovidgoyal/kitty/issues/1238
-        if (s == 0 && yoffset != 0) s = yoffset > 0 ? 1 : -1;
+        if (s == 0) s = yoffset > 0 ? 1 : -1;
         screen->pending_scroll_pixels = 0;
     }
 #undef SCALE_SCROLL

kitty/options/definition.py

@@ -347,6 +347,16 @@ as macOS and Wayland. Use negative numbers to change scroll direction.
 '''
     )
 
+opt('wheel_scroll_min_lines', '1',
+    option_type='int', ctype='int',
+    long_text='''
+The minimum number of lines scrolled by the mouse wheel. The scrolling
+acceleration only takes effect after it reaches the number. Note that this is
+only used for low precision scrolling devices. With a negative number, the
+minimum number of lines will always be added.
+'''
+    )
+
 opt('touch_scroll_multiplier', '1.0',
     option_type='float', ctype='double',
     long_text='''

kitty/options/parse.py

@@ -1272,6 +1272,9 @@ class Parser:
     def wayland_titlebar_color(self, val: str, ans: typing.Dict[str, typing.Any]) -> None:
         ans['wayland_titlebar_color'] = titlebar_color(val)
 
+    def wheel_scroll_min_lines(self, val: str, ans: typing.Dict[str, typing.Any]) -> None:
+        ans['wheel_scroll_min_lines'] = int(val)
+
     def wheel_scroll_multiplier(self, val: str, ans: typing.Dict[str, typing.Any]) -> None:
         ans['wheel_scroll_multiplier'] = float(val)
 

kitty/options/to-c-generated.h

@@ -187,6 +187,19 @@ convert_from_opts_wheel_scroll_multiplier(PyObject *py_opts, Options *opts) {
     Py_DECREF(ret);
 }
 
+static void
+convert_from_python_wheel_scroll_min_lines(PyObject *val, Options *opts) {
+    opts->wheel_scroll_min_lines = PyLong_AsLong(val);
+}
+
+static void
+convert_from_opts_wheel_scroll_min_lines(PyObject *py_opts, Options *opts) {
+    PyObject *ret = PyObject_GetAttrString(py_opts, "wheel_scroll_min_lines");
+    if (ret == NULL) return;
+    convert_from_python_wheel_scroll_min_lines(ret, opts);
+    Py_DECREF(ret);
+}
+
 static void
 convert_from_python_touch_scroll_multiplier(PyObject *val, Options *opts) {
     opts->touch_scroll_multiplier = PyFloat_AsDouble(val);
@@ -1023,6 +1036,8 @@ convert_opts_from_python_opts(PyObject *py_opts, Options *opts) {
     if (PyErr_Occurred()) return false;
     convert_from_opts_wheel_scroll_multiplier(py_opts, opts);
     if (PyErr_Occurred()) return false;
+    convert_from_opts_wheel_scroll_min_lines(py_opts, opts);
+    if (PyErr_Occurred()) return false;
     convert_from_opts_touch_scroll_multiplier(py_opts, opts);
     if (PyErr_Occurred()) return false;
     convert_from_opts_mouse_hide_wait(py_opts, opts);

kitty/options/types.py

@@ -437,6 +437,7 @@ option_names = (  # {{{
  'visual_window_select_characters',
  'watcher',
  'wayland_titlebar_color',
+ 'wheel_scroll_min_lines',
  'wheel_scroll_multiplier',
  'window_alert_on_bell',
  'window_border_width',
@@ -580,6 +581,7 @@ class Options:
     visual_bell_duration: float = 0
     visual_window_select_characters: str = '1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ'
     wayland_titlebar_color: int = 0
+    wheel_scroll_min_lines: int = 1
     wheel_scroll_multiplier: float = 5.0
     window_alert_on_bell: bool = True
     window_border_width: typing.Tuple[float, str] = (0.5, 'pt')

kitty/state.h

@@ -24,6 +24,7 @@ typedef struct {
 typedef struct {
     monotonic_t visual_bell_duration, cursor_blink_interval, cursor_stop_blinking_after, mouse_hide_wait, click_interval;
     double wheel_scroll_multiplier, touch_scroll_multiplier;
+    int wheel_scroll_min_lines;
     bool enable_audio_bell;
     CursorShape cursor_shape;
     float cursor_beam_thickness;