"""PyQt5 widgets to render 'MIDI tape loop' generator graphics.
"""

# Inspired by Brian Eno's "Music for Airports" and
# "JavaScript Systems Music" https://teropa.info/blog/2016/07/28/javascript-systems-music.html#brian-enoambient-1-music-for-airports-2-11978

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# Written in 2019 by Garth Zeglin <garthz@cmu.edu>

# To the extent possible under law, the author has dedicated all copyright
# and related and neighboring rights to this software to the public domain
# worldwide. This software is distributed without any warranty.

# You should have received a copy of the CC0 Public Domain Dedication along with this software.
# If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.

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import math, logging

# for documentation on the PyQt5 API, see http://pyqt.sourceforge.net/Docs/PyQt5/index.html
from PyQt5 import QtCore, QtGui, QtWidgets

# set up logger for module
log = logging.getLogger('QtConcentricLoops')

# filter out most logging; the default is NOTSET which passes along everything
# log.setLevel(logging.WARNING)

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[docs]class QtConcentricLoops(QtWidgets.QWidget):
    """Custom widget representing a MIDI 'tape loop' generator."""

    def __init__(self, channels=7):
        super().__init__()
        self.setMinimumSize(QtCore.QSize(100, 100))
        self.setAutoFillBackground(True)

        # graphical state variables
        self.channels = channels
        self.positions = [0.0]*self.channels # units are degrees

        # Create a path representing the basic concentric circles structure.
        # The default coordinates have +X to the right, +Y down.  The drawing
        # units are notionally millimeters (although the graphic is abstract).
        self.track_symbol = QtGui.QPainterPath()
        for i in range(channels):
            r = 25 + 12*i
            self.track_symbol.addEllipse(QtCore.QPointF(0.0, 0.0), r-5, r-5)  # center, rx, ry
            self.track_symbol.addEllipse(QtCore.QPointF(0.0, 0.0), r+5, r+5)  # center, rx, ry
        self.track_symbol.moveTo(12,0)         # draw the play bar
        self.track_symbol.lineTo(26 + 12*self.channels, 0)

        # finish initialization
        self.show()
        return

[docs]    def update_positions(self, positions):
        N = len(positions)
        self.positions[0:N] = positions
        self.repaint()

    # === element drawing methods ============================================================

    # === Qt API methods ============================================================
[docs]    def paintEvent(self, e):
        """Subclass implementation of parent QWidget class callback to repaint the graphics."""
        geometry = self.geometry()
        view_width = geometry.width()
        view_height = geometry.height()

        # clear the background
        qp = QtGui.QPainter()
        qp.begin(self)
        qp.fillRect(QtCore.QRectF(0, 0, view_width, view_height), QtCore.Qt.white)
        # qp.setRenderHint(QtGui.QPainter.Antialiasing)

        # Set up a coordinate system scaled to real-world millimeters, centered
        # in the visible area, keeping the minimum visible area in view.

        # define minimum visible area
        scene_width   = 20 + 10 + 20 + 24*self.channels
        scene_height  = scene_width
        scene_aspect  = scene_width / scene_height
        view_aspect = view_width / view_height
        if scene_aspect > view_aspect:
            scaling = view_width / scene_width
        else:
            scaling = view_height/scene_height

        qp.save()
        qp.translate(QtCore.QPointF(view_width/2, view_height/2))
        qp.scale(scaling, scaling)

        # draw the track at scale
        pen = QtGui.QPen(QtCore.Qt.black)
        pen.setWidthF(0.5)
        qp.setPen(pen)
        brush = QtGui.QBrush(QtGui.QColor(240, 240, 240, 255))
        qp.setBrush(brush)
        qp.drawPath(self.track_symbol)

        # draw the position markers
        brush = QtGui.QBrush(QtCore.Qt.red)
        qp.setBrush(brush)
        for i, angle in enumerate(self.positions):
            r = 25 + 12*i
            theta = angle * math.pi/180
            # draw the markers at a position such that angles increase CCW, i.e. +Z is out of the screen
            qp.drawEllipse(QtCore.QPointF(r * math.cos(theta), -r * math.sin(theta)), 5, 5)

        # restore the initial unscaled coordinates
        qp.restore()
        qp.end()

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