textbox: copy curses.textpad, restrict to 1 line

bebop/command_line.py

@@ -2,7 +2,6 @@
 
 import curses
 import curses.ascii
-import curses.textpad
 import os
 import logging
 import tempfile
@@ -10,6 +9,7 @@ from typing import Optional
 
 from bebop.external import open_external_program
 from bebop.links import Links
+from bebop.textbox import Textbox
 
 
 class CommandLine:
@@ -33,7 +33,7 @@ class CommandLine:
     def __init__(self, window, editor_command):
         self.window = window
         self.editor_command = editor_command
-        self.textbox = curses.textpad.Textbox(self.window)
+        self.textbox = Textbox(self.window, insert_mode=True)
 
     def clear(self):
         """Clear command-line contents."""

bebop/textbox.py

@@ -0,0 +1,166 @@
+"""Fork of Python's standard library curses.textpad module.
+
+I guess it requires some license header?
+
+Copyright (c) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011,
+2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020, 2021
+Python Software Foundation;
+All Rights Reserved
+
+This version fixes a few quirks of the standard module, namely:
+
+- Discard multi-lines mode: only one line is supported.
+"""
+
+import curses
+import curses.ascii
+import logging
+
+
+class Textbox:
+    """Editing widget using the interior of a window object.
+
+    - Ctrl-A: Go to left edge of window.
+    - Ctrl-B: Cursor left, wrapping to previous line if appropriate.
+    - Ctrl-D: Delete character under cursor.
+    - Ctrl-E: Go to right edge (stripspaces off) or end of line (stripspaces on).
+    - Ctrl-F: Cursor right, wrapping to next line when appropriate.
+    - Ctrl-H: Delete character backward.
+    - Ctrl-K: If line is blank, delete it, otherwise clear to end of line.
+    - Ctrl-L: Refresh screen.
+
+    Move operations do nothing if the cursor is at an edge where the movement
+    is not possible.  The following synonyms are supported where possible:
+
+    - KEY_LEFT: Ctrl-B
+    - KEY_RIGHT: Ctrl-F
+    - KEY_UP: Ctrl-P
+    - KEY_DOWN: Ctrl-N
+    - KEY_BACKSPACE: Ctrl-H
+    """
+    def __init__(self, win, insert_mode=False):
+        self.win = win
+        self.insert_mode = insert_mode
+        self._update_max_yx()
+        self.stripspaces = True
+        self.lastcmd = None
+        win.keypad(1)
+
+    def _update_max_yx(self):
+        maxy, maxx = self.win.getmaxyx()
+        self.maxy = maxy - 1
+        self.maxx = maxx - 1
+
+    def _end_of_line(self):
+        """Go to the location of the first blank."""
+        logging.debug(f"_end_of_line")
+        self._update_max_yx()
+        logging.debug(f"_end_of_line {self.win.getyx()} {(self.maxx, self.maxy)}")
+        last = self.maxx
+        while True:
+            if curses.ascii.ascii(self.win.inch(0, last)) != curses.ascii.SP:
+                last = min(self.maxx, last + 1)
+                break
+            elif last == 0:
+                break
+            last = last - 1
+        return last
+
+    def _insert_printable_char(self, ch):
+        logging.debug(f"_insert_printable_char {ch}")
+        self._update_max_yx()
+        y, x = self.win.getyx()
+        backyx = None
+        while x < self.maxx:
+            oldch = 0
+            if self.insert_mode:
+                oldch = self.win.inch()
+            # The try-catch ignores the error we trigger from some curses
+            # versions by trying to write into the lowest-rightmost spot
+            # in the window.
+            try:
+                self.win.addch(ch)
+            except curses.error:
+                pass
+            if not self.insert_mode or not curses.ascii.isprint(oldch):
+                break
+            ch = oldch
+            y, x = self.win.getyx()
+            # Remember where to put the cursor back since we are in insert_mode
+            if backyx is None:
+                backyx = y, x
+
+        if backyx is not None:
+            self.win.move(*backyx)
+
+    def do_command(self, ch):
+        """Process a single editing command."""
+        logging.debug(f"do_command {ch}")
+        self._update_max_yx()
+        _, x = self.win.getyx()
+        self.lastcmd = ch
+        if curses.ascii.isprint(ch):
+            if x < self.maxx:
+                self._insert_printable_char(ch)
+        elif ch == curses.ascii.NL:
+            return 0
+        elif ch == curses.ascii.SOH:                      # ^a
+            self.win.move(0, 0)
+        elif ch in (
+            curses.ascii.STX,
+            curses.KEY_LEFT,
+            curses.ascii.BS,
+            curses.KEY_BACKSPACE
+        ):
+            if x > 0:
+                self.win.move(0, x - 1)
+            if ch in (curses.ascii.BS, curses.KEY_BACKSPACE):
+                self.win.delch()
+        elif ch == curses.ascii.EOT:                      # ^d
+            self.win.delch()
+        elif ch == curses.ascii.ENQ:                      # ^e
+            if self.stripspaces:
+                self.win.move(0, self._end_of_line())
+            else:
+                self.win.move(0, self.maxx)
+            self.win.move(0, self.maxx)
+        elif ch in (curses.ascii.ACK, curses.KEY_RIGHT):  # ^f
+            if x < self.maxx:
+                self.win.move(0, x + 1)
+        elif ch == curses.ascii.VT:                       # ^k
+            if x == 0 and self._end_of_line() == 0:
+                self.win.deleteln()
+            else:
+                # First undo the effect of self._end_of_line.
+                self.win.move(0, x)
+                self.win.clrtoeol()
+        elif ch == curses.ascii.FF:                       # ^l
+            self.win.refresh()
+        return 1
+
+    def gather(self):
+        """Collect and return the contents of the window."""
+        result = ""
+        self._update_max_yx()
+        self.win.move(0, 0)
+        stop = self._end_of_line()
+        for x in range(self.maxx + 1):
+            if self.stripspaces and x > stop:
+                break
+            result = result + chr(curses.ascii.ascii(self.win.inch(0, x)))
+        if self.maxy > 0:
+            result = result + "\n"
+        return result
+
+    def edit(self, validate=None):
+        """Edit in the widget window and collect the results."""
+        while True:
+            ch = self.win.getch()
+            if validate:
+                ch = validate(ch)
+            if not ch:
+                continue
+            if not self.do_command(ch):
+                break
+            self.win.refresh()
+        return self.gather()