add support for backword

babi/file.py

@@ -608,6 +608,46 @@ def backspace(self, dim: Dim) -> None:
             self.buf[self.buf.y] = s[:self.buf.x - 1] + s[self.buf.x:]
             self.buf.left(dim)
 
+    @edit_action('backword text', final=False)
+    @clear_selection
+    def backword(self, dim: Dim) -> None:
+        line = self.buf[self.buf.y]
+        if self.buf.x == 0 and self.buf.y == 0:
+            pass
+        # backword at the end of the file does not change the contents
+        elif (
+                self.buf.y == len(self.buf) - 1 and
+                # still allow backword if there are 2+ blank lines
+                self.buf[self.buf.y - 1] != ''
+        ):
+            self.buf.left(dim)
+        elif self.buf.x == 0:
+            y, victim = self.buf.y, self.buf.pop(self.buf.y)
+            self.buf.left(dim)
+            self.buf[y - 1] += victim
+        elif self.buf.x > 0 and line[:self.buf.x].isspace():
+            while self.buf.x > 0:
+                s = self.buf[self.buf.y]
+                self.buf[self.buf.y] = s[:self.buf.x - 1] + s[self.buf.x:]
+                self.buf.left(dim)
+        else:
+            tp = line[self.buf.x - 1].isalnum()
+            # we keep track of whether we're deleting spaces
+            are_spaces = line[self.buf.x - 1].isspace()
+            while self.buf.x > 0 and tp == line[self.buf.x - 1].isalnum():
+                s = self.buf[self.buf.y]
+                self.buf[self.buf.y] = s[:self.buf.x - 1] + s[self.buf.x:]
+                self.buf.left(dim)
+
+            # if we were deleting spaces, this means we haven't deleted the
+            # word yet
+            tp = line[self.buf.x - 1].isalnum()
+            if are_spaces:
+                while self.buf.x > 0 and line[self.buf.x - 1].isalnum():
+                    s = self.buf[self.buf.y]
+                    self.buf[self.buf.y] = s[:self.buf.x - 1] + s[self.buf.x:]
+                    self.buf.left(dim)
+
     @edit_action('delete text', final=False)
     @clear_selection
     def delete(self, dim: Dim) -> None:
@@ -901,6 +941,7 @@ def reload(self, status: Status, dim: Dim) -> None:
         b'kDN3': alt_down,
         # editing
         b'KEY_BACKSPACE': backspace,
+        b'KEY_BACKWORD': backword,
         b'KEY_DC': delete,
         b'^M': enter,
         b'^I': tab,

babi/screen.py

@@ -67,6 +67,7 @@
     '\x1b[1;6H': b'kHOM6',  # Shift + ^Home
     '\x1b[1;6F': b'kEND6',  # Shift + ^End
     '\x1b[~': b'KEY_BTAB',  # Shift + Tab
+    '\x1b(263)': b'KEY_BACKWORD',  # M-Backspace
 }
 KEYNAME_REWRITE = {
     # windows-curses: numeric pad arrow keys

tests/features/conftest.py

@@ -268,6 +268,7 @@ def value(self) -> int:
     Key('^End', b'kEND5', 530),
     Key('^S-Up', b'kUP6', 567),
     Key('^S-Down', b'kDN6', 526),
+    Key('M-BSpace', b'KEY_BACKWORD', 504),
     Key('M-Up', b'kUP3', 564),
     Key('M-Down', b'kDN3', 523),
     Key('M-Right', b'kRIT3', 558),

tests/features/text_editing_test.py

@@ -79,6 +79,85 @@ def test_backspace_deletes_text(run, tmpdir, key):
         h.await_cursor_position(x=2, y=1)
 
 
+def test_backword_at_beginning_of_file(run):
+    # same behavior as backspace
+    with run() as h, and_exit(h):
+        h.press('M-BSpace')
+        h.await_text_missing('unknown key')
+        h.assert_cursor_line_equal('')
+        h.await_text_missing('*')
+
+
+def test_backword_joins_lines(run, tmpdir):
+    # same behavior as backspace
+    f = tmpdir.join('f')
+    f.write('foo\nbar\nbaz\n')
+
+    with run(str(f)) as h, and_exit(h):
+        h.await_text('foo')
+        h.press('Down')
+        h.press('M-BSpace')
+        h.await_text('foobar')
+        h.await_text('f *')
+        h.await_cursor_position(x=3, y=1)
+        # pressing down should retain the X position
+        h.press('Down')
+        h.await_cursor_position(x=3, y=2)
+
+
+def test_backword_at_end_of_file_still_allows_scrolling_down(run, tmpdir):
+    f = tmpdir.join('f')
+    f.write('hello world')
+
+    with run(str(f)) as h, and_exit(h):
+        h.await_text('hello world')
+        h.press('Down')
+        h.press('M-BSpace')
+        h.press('Down')
+        h.await_cursor_position(x=0, y=2)
+        h.await_text_missing('*')
+
+
+def test_backword_deletes_newline_at_end_of_file(run, tmpdir):
+    f = tmpdir.join('f')
+    f.write('foo\n\n')
+
+    with run(str(f)) as h, and_exit(h):
+        h.press('^End')
+        h.press('M-BSpace')
+        h.press('^S')
+
+    assert f.read() == 'foo\n'
+
+
+def test_backword_deletes_text(run, tmpdir):
+    f = tmpdir.join('f')
+    f.write('ohai there')
+
+    with run(str(f)) as h, and_exit(h):
+        h.await_text('ohai there')
+        for _ in range(3):
+            h.press('Right')
+        h.press('M-BSpace')
+        h.await_text('i')
+        h.await_text('f *')
+        h.await_cursor_position(x=0, y=1)
+
+
+def test_backword_deletes_text_with_space_after(run, tmpdir):
+    f = tmpdir.join('f')
+    f.write('ohai there   ')
+
+    with run(str(f)) as h, and_exit(h):
+        h.await_text('ohai there')
+        for _ in range(13):
+            h.press('Right')
+        h.press('M-BSpace')
+        h.await_text('ohai')
+        h.await_text('f *')
+        h.await_cursor_position(x=5, y=1)
+
+
 def test_delete_at_end_of_file(run, tmpdir):
     with run() as h, and_exit(h):
         h.press('DC')