.. _sequence example:

================================
Animating with control sequences
================================

.. py:currentmodule:: chafa

This is a fun little example that demonstrates how to use the :py:meth:`TermInfo.emit` method.

.. image:: example_img/animation.gif
    :width: 300
    :align: center

The code that produced this animation follows:

::

    from chafa import *
    from time import sleep
    import sys

    SL=15

    def snake(n, step):
        if step < 0: turns = ["┏","┛"]
        else:        turns = ["┓", "┗"]

        if n == 1:
            return turns[0]
        elif n == SL - 1:
            return turns[1]

        return "┃"

    def gradient(x, y):
        return (80 + 5*x, 255 - (100 + 10*y), 200)

    # Grab our info
    db = TermDb()
    info = db.detect()

    # Clear the terminal
    clear     = info.emit(TermSeq.CHAFA_TERM_SEQ_CLEAR)
    no_cursor = info.emit(TermSeq.CHAFA_TERM_SEQ_DISABLE_CURSOR)

    print(clear.decode())
    print(no_cursor.decode())

    rows = list(range(1,SL))
    cols = list(range(1,32))

    for x in cols:
        # We want to step backwards if column is even
        step = 2 * (x%2) - 1

        for y in rows[::step]:
            # Grab char
            char = snake(y, step)

            # Move to position
            out = info.emit(
                TermSeq.CHAFA_TERM_SEQ_CURSOR_TO_POS, 
                x, y
            )

            # Set color
            color = info.emit(
                TermSeq.CHAFA_TERM_SEQ_SET_COLOR_FG_DIRECT,
                *gradient(x,y)
            )

            sys.stdout.buffer.write(out)
            sys.stdout.buffer.write(color)
            sys.stdout.write(char)
            sys.stdout.flush()

            sleep(0.01)

    # All back to normal!
    reset = info.emit(TermSeq.CHAFA_TERM_SEQ_RESET_TERMINAL_HARD)
    print(reset.decode())