support truecolor in prompt_toolkit sessions

Support truecolor in prompt_toolkit sessions if the environment
variable COLORTERM contains "truecolor"; otherwise fall back to 8-bit
color depth, the prompt_tookit default.

Author: rolandwalker

changelog.md

@@ -9,6 +9,7 @@ Features
 * Optionally defer auto-completions until a minimum number of characters is typed.
 * Make the completion interface more responsive using a background thread.
 * Option to suppress control-d exit behavior.
+* Better support Truecolor terminals.
 
 
 Bug Fixes

mycli/main.py

@@ -42,6 +42,7 @@
 from prompt_toolkit.key_binding.key_processor import KeyPressEvent
 from prompt_toolkit.layout.processors import ConditionalProcessor, HighlightMatchingBracketProcessor
 from prompt_toolkit.lexers import PygmentsLexer
+from prompt_toolkit.output import ColorDepth
 from prompt_toolkit.shortcuts import CompleteStyle, PromptSession
 import pymysql
 from pymysql.constants.ER import HANDSHAKE_ERROR
@@ -1168,6 +1169,7 @@ def one_iteration(text: str | None = None) -> None:
                 editing_mode = EditingMode.EMACS
 
             self.prompt_app = PromptSession(
+                color_depth=ColorDepth.DEPTH_24_BIT if 'truecolor' in os.getenv('COLORTERM', '').lower() else None,
                 lexer=PygmentsLexer(MyCliLexer),
                 reserve_space_for_menu=self.get_reserved_space(),
                 message=get_message,