Move implementation of screen_line() into C

kitty/char_grid.py

@@ -301,13 +301,7 @@ class CharGrid:
 
     def screen_line(self, y):
         ' Return the Line object corresponding to the yth line on the rendered screen '
-        if y >= 0 and y < self.screen.lines:
+        return self.screen.visual_line(y, self.scrolled_by)
-            if self.scrolled_by:
-                if y < self.scrolled_by:
-                    return self.screen.historybuf.line(self.scrolled_by - 1 - y)
-                return self.screen.line(y - self.scrolled_by)
-            else:
-                return self.screen.line(y)
 
     def multi_click(self, count, x, y):
         x, y = self.cell_for_pos(x, y)

kitty/screen.c

@@ -1078,6 +1078,25 @@ line(Screen *self, PyObject *val) {
     return (PyObject*) self->linebuf->line;
 }
 
+static PyObject*
+visual_line(Screen *self, PyObject *args) {
+    // The line corresponding to the yth visual line, taking into account scrolling
+    unsigned int y, scrolled_by;
+    if (!PyArg_ParseTuple(args, "II", &y, &scrolled_by)) return NULL;
+    if (y >= self->lines) { Py_RETURN_NONE; }
+    if (scrolled_by) {
+        if (y < scrolled_by) {
+            historybuf_init_line(self->historybuf, scrolled_by - 1 - y, self->historybuf->line);
+            Py_INCREF(self->historybuf->line);
+            return (PyObject*) self->historybuf->line;
+        } 
+        y -= scrolled_by;
+    }
+    linebuf_init_line(self->linebuf, y);
+    Py_INCREF(self->linebuf->line);
+    return (PyObject*) self->linebuf->line;
+}
+ 
 static PyObject*
 draw(Screen *self, PyObject *src) {
     if (!PyUnicode_Check(src)) { PyErr_SetString(PyExc_TypeError, "A unicode string is required"); return NULL; }
@@ -1271,6 +1290,7 @@ COUNT_WRAP(cursor_forward)
 
 static PyMethodDef methods[] = {
     MND(line, METH_O)
+    MND(visual_line, METH_VARARGS)
     MND(draw, METH_O)
     MND(cursor_position, METH_VARARGS)
     MND(set_mode, METH_VARARGS)