ReplView

Header: examples/UI/REPL/ReplView.h
Namespace: global

ReplView is a terminal-style REPL (Read-Eval-Print Loop) UI framework built on M5GFX LGFX_Sprite (canvas). It provides a keyboard-driven interface with a prompt, input buffer, cursor blinking, and command callbacks. Useful for building interactive shells, debug consoles, or text-based UIs on the M5Cardputer.

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Callbacks

onRenderTips

std::function<void()> onRenderTips;

Called during init() after clearing the screen. Use this to render header text, usage hints, or ASCII art at the top of the screen.

repl.onRenderTips = []() {
    M5Cardputer.Display.println("=== My App v1.0 ===");
    M5Cardputer.Display.println("Type 'help' for commands");
};

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onCommand

std::function<void(const std::string& command)> onCommand;

Called when the user presses Enter with a non-empty input buffer. Receives the raw command string.

repl.onCommand = [](const std::string& cmd) {
    if (cmd == "help") {
        M5Cardputer.Display.println("Available: help, clear, exit");
    } else if (cmd == "clear") {
        // ...
    }
};

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Fields

autoClearPrompt

bool autoClearPrompt = true;

When true (default), the input buffer is automatically cleared after onCommand is called. Set to false if you want to retain the input buffer after command execution.

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Methods

init(canvas)

void init(LGFX_Sprite* canvas);

Initialize the REPL on a given canvas. Calls render_interface() which: 1. Clears the screen to black 2. Sets default font (efontCN_16) and text scroll mode 3. Calls onRenderTips if set 4. Renders the initial prompt

Parameter	Type	Description
canvas	LGFX_Sprite*	Pointer to an LGFX_Sprite (usually &M5Cardputer.Display)

ReplView repl;
repl.init(&M5Cardputer.Display);

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update()

void update();

Call every loop() iteration. Handles: - Keyboard input via M5Cardputer.Keyboard (calls isChange() + keysState()) - Blinking cursor every 500ms - Enter key → calls onCommand callback - Backspace key → removes last character from input buffer - Printable characters → appended to input buffer

void loop() {
    M5Cardputer.update();
    repl.update();
}

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clearScreen()

void clearScreen();

Clears the entire screen (fills black, resets cursor to top-left, pushes sprite).

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showMessage(message, color)

void showMessage(const std::string& message, uint16_t color = TFT_WHITE);

Prints a line of text to the canvas and pushes it to the display. Useful for outputting results after commands.

Parameter	Type	Default	Description
message	const std::string&	—	Text to display
color	uint16_t	TFT_WHITE	Text color

repl.showMessage("Command executed.", TFT_GREEN);
repl.showMessage("Error: invalid input", TFT_RED);

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showPrompt(prompt_text)

void showPrompt(const std::string& prompt_text = ">>> ");

Changes the prompt text displayed before the input cursor and re-renders the current line.

Parameter	Type	Default	Description
prompt_text	const std::string&	">>> "	New prompt string

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setPromptText(prompt)

void setPromptText(const std::string& prompt);

Changes the prompt text without re-rendering. Use showPrompt() if you want immediate visual update; use setPromptText() if you want the change to appear on the next render cycle.

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setInputBuffer(text)

void setInputBuffer(const std::string& text);

Sets the current input buffer content and re-renders the prompt line. Used for programmatic input injection.

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getInputBuffer()

const std::string& getInputBuffer() const;

Returns the current input buffer content.

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clearInputBuffer()

void clearInputBuffer();

Clears the input buffer and re-renders the prompt.

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Complete Example

#include <M5Cardputer.h>
#include "examples/UI/REPL/ReplView.h"

ReplView repl;

void setup() {
    auto cfg = M5.config();
    M5Cardputer.begin(cfg, true);

    repl.onRenderTips = []() {
        M5Cardputer.Display.println("=== REPL Demo ===");
        M5Cardputer.Display.println("Commands: help, hello, clear");
    };

    repl.onCommand = [](const std::string& cmd) {
        if (cmd == "help") {
            repl.showMessage("help - show this message", TFT_CYAN);
            repl.showMessage("hello - greet", TFT_CYAN);
            repl.showMessage("clear - clear screen", TFT_CYAN);
        } else if (cmd == "hello") {
            repl.showMessage("Hello, M5Cardputer!", TFT_GREEN);
        } else if (cmd == "clear") {
            repl.clearScreen();
            repl.onRenderTips();
            repl.showPrompt();
        } else {
            repl.showMessage("Unknown: " + cmd, TFT_RED);
        }
    };

    repl.init(&M5Cardputer.Display);
}

void loop() {
    M5Cardputer.update();
    repl.update();
}

Note

ReplView is distributed as an example class, not part of the src/ library. To use it, copy ReplView.h and ReplView.cpp into your project or add the examples directory to your include path.