1 files changed, 66 insertions, 0 deletions
diff --git a/cmd2/rl_utils.py b/cmd2/rl_utils.py
new file mode 100644
index 00000000..d5bef1ff
--- /dev/null
+++ b/cmd2/rl_utils.py
@@ -0,0 +1,66 @@
+# coding=utf-8
+"""
+Imports the proper readline for the platform and provides utility functions for it
+"""
+import sys
+
+try:
+    from enum34 import Enum
+except ImportError:
+    from enum import Enum
+
+# Prefer statically linked gnureadline if available (for macOS compatibility due to issues with libedit)
+try:
+    import gnureadline as readline
+except ImportError:
+    # Try to import readline, but allow failure for convenience in Windows unit testing
+    # Note: If this actually fails, you should install readline on Linux or Mac or pyreadline on Windows
+    try:
+        # noinspection PyUnresolvedReferences
+        import readline
+    except ImportError:  # pragma: no cover
+        pass
+
+
+class RlType(Enum):
+    """Readline library types we recognize"""
+    GNU = 1
+    PYREADLINE = 2
+    NONE = 3
+
+
+# Check what implementation of readline we are using
+
+rl_type = RlType.NONE
+
+# The order of this check matters since importing pyreadline will also show readline in the modules list
+if 'pyreadline' in sys.modules:
+    rl_type = RlType.PYREADLINE
+
+elif 'gnureadline' in sys.modules or 'readline' in sys.modules:
+    rl_type = RlType.GNU
+
+    # Load the readline lib so we can access members of it
+    import ctypes
+    readline_lib = ctypes.CDLL(readline.__file__)
+
+
+def rl_force_redisplay() -> None:
+    """
+    Causes readline to redraw prompt and input line
+    """
+    if not sys.stdout.isatty():
+        return
+
+    if rl_type == RlType.GNU:  # pragma: no cover
+        # rl_forced_update_display() is the proper way to redraw the prompt and line, but we
+        # have to use ctypes to do it since Python's readline API does not wrap the function
+        readline_lib.rl_forced_update_display()
+
+        # After manually updating the display, readline asks that rl_display_fixed be set to 1 for efficiency
+        display_fixed = ctypes.c_int.in_dll(readline_lib, "rl_display_fixed")
+        display_fixed.value = 1
+
+    elif rl_type == RlType.PYREADLINE:  # pragma: no cover
+        # noinspection PyProtectedMember
+        readline.rl.mode._print_prompt()