End DCS/OSC strings at any ESC, default the external terminal to Terminal.app

A string with no ST swallowed every later sequence, RIS included, and
Clear Screen could not recover the tab. Any ESC now ends it, as in xterm,
and the sequence it starts is dispatched. The shipped setting needed Kitty.

Also: REP, SCOSC/SCORC, DECOM-relative CPR, `:` subparams and more DECRQM
modes answered; new rows inserted in one edit; controls stripped from
pastes; wide-char mouse columns.

tests/test_render.py

@@ -357,7 +357,13 @@ command = make_command(terminal)
 stream.feed("".join("\x1b[31mr{}\x1b[0m\r\n".format(i) for i in range(300)))
 command.update_lines(None, terminal)
 terminal.screen.dirty.clear()
-assert set(command.state.archived_chunks) == {0}, command.state.archived_chunks
+# rows new to the view went in as one insert, coloured straight onto their
+# chunk keys; only row 0 and the two coloured screen rows have a key of their own
+assert set(command.state.archived_chunks) == {0, 1}, command.state.archived_chunks
+assert len(terminal.view.regions["vterm@1@vterm.red.default"][1]) == terminal.offset - CHUNK
+row_keys = [k for k in terminal.view.regions if k.startswith("vterm#")]
+assert len(row_keys) == 3, row_keys
+assert terminal.view.text.split("\n")[:3] == ["r0", "r1", "r2"], terminal.view.text[:20]
 command.trim_history(None, terminal)
 assert "vterm@0@vterm.red.default" not in terminal.view.regions, "trimmed chunk key left behind"
 assert 0 not in command.state.archived_chunks
@@ -665,7 +671,15 @@ terminal.view.window_to_text = lambda xy: terminal.view.text_point(2, 4)
 mouse_release.run(None, event)
 assert terminal.process.written == "\x1b[<0;1;1M\x1b[<32;5;3M\x1b[<0;5;3m", repr(terminal.process.written)
 
-print("click tests passed (first click focuses only; press, drag and release report)")
+# the column is counted in cells: a wide char before the point takes two
+terminal.process.writes.clear()
+terminal.view.text = "\u65e5\u672cx   \nr1    \nr2    \nr3    \nr4    \n"
+terminal.view.window_to_text = lambda xy: terminal.view.text_point(0, 2)
+mouse_press.run(None, event)
+mouse_release.run(None, event)
+assert terminal.process.written == "\x1b[<0;5;1M\x1b[<0;5;1m", repr(terminal.process.written)
+
+print("click tests passed (first click focuses only; press, drag and release report; wide chars)")
 
 
 # entering the alt screen folds the scrollback away (kitty hides it); leaving
@@ -751,4 +765,12 @@ line[0] = Char("r", "red", "default", False, False, False, False, True)
 runs = [r for r in segment_buffer_line(line) if r[1] != r[2]]
 assert runs == [("r", 0, 1, "reverse_default", "red", "")], runs
 
-print("segmenter tests passed (leading gap, wide char, orphan filler, reverse)")
+# a cell can hold two code points (a mark NFC could not compose): the spans
+# that follow are offsets into the row text, so they move by two
+line = StaticDefaultDict(Char(" "))
+line[0] = Char("q\u0301", "default", "default")
+line[1] = Char("x", "blue", "default")
+runs = [r for r in segment_buffer_line(line) if r[1] != r[2]]
+assert runs == [("q\u0301", 0, 2, "default", "default", ""), ("x", 2, 3, "blue", "default", "")], runs
+
+print("segmenter tests passed (leading gap, wide char, orphan filler, reverse, two-code-point cell)")