clusterview/clusterview/opengl_widget.py

"""
This module defines functions that need to be overwritten
in order for OpenGL to work with the main window. This
module is named the same as the actual widget in order
to make namespacing consistent.

To be clear, the actual widget is defined in the UI
generated code - `clusterview_ui.py`. The functions
here are imported as overrides to the OpenGL functions of
that widget.
"""

from enum import Enum

from OpenGL.GL import (glBegin, glClearColor, glColor4f, glEnable,
                       glEnd, GL_LIGHT0, GL_LIGHTING, GL_POINTS,
                       glPointSize, glVertex3f, glViewport)

from .exceptions import InvalidModeError, InvalidStateError
from .mode import Mode
from .points import PointSet

class Color(Enum):
    BLUE = 0

# A simple map from Color -> RGBA 4-Tuple
# Note: The color values in the tuple are not RGB, but
#       rather OpenGL percentage values for RGB.
COLOR_TO_RGBA = {
    Color.BLUE: (0, 0.5, 1.0, 0.0)
}

# Constants set based on the size of the window.
__BOTTOM_LEFT = (0, 0)
__WIDTH = None
__HEIGHT = None

# Module-global state variables for our drawing
# state machine.
#
# Below functions have to mark these as `global` so
# the interpreter knows that the variables are not
# function local.
__current_mode = None
__current_event = None
__current_points = None
__current_context = None


def set_drawing_context(ctx):
    """
    Sets the drawing context so that drawing functions can properly
    interact with the widget.
    """
    global __current_context

    __current_context = ctx

def set_current_points(points):
    """
    Sets the point state variable that will be passed in to the paint_gl
    function, and further to the point painter functions in order to
    render the scene.

    Each time a point is added, removed, or edited this point set must be
    updated.

    @param points The PointSet representing the current scene.
    """
    global __current_points

    if not isinstance(points, PointSet):
        raise ValueError("set_current_points must recieve a PointSet as its " +
                         "argument.")

    __current_points = points


def set_drawing_mode(mode):
    """
    State management function. It is useful to look at the
    different drawing modes as modes in a state machine.

    Calling this function when a mode changes allows the
    OpenGL functions to take the correct drawing action
    on the OpenGL Widget.

    @param mode The current mode.
    """
    global __current_context
    global __current_mode

    if __current_context is None:
        raise InvalidStateError("Drawing context must be set before setting " +
                                "drawing mode")

    if not isinstance(mode, Mode):
        raise ValueError("Mode in set_drawing_mode must be of type Mode")

    __current_mode = mode


def set_drawing_event(event):
    """
    State machine event management function.

    @param event The event.
    """
    global __current_context
    global __current_event

    if __current_context is None:
        raise InvalidStateError("Drawing context must be set before setting " +
                                "drawing mode")

    if event is not None:
        __current_event = event


def initialize_gl():
    """
    Initializes the OpenGL context on the Window.
    """
    # Since we aren't using shaders lighting needs to be
    # enabled.
    glEnable(GL_LIGHTING);
    glEnable(GL_LIGHT0);

    # Set white background
    glClearColor(255, 255, 255, 0)


def resize_gl(w, h):
    """
    OpenGL resize handler used to get the current viewport size.

    @param w The new width.
    @param h The new height.
    """
    global __WIDTH
    global __HEIGHT

    __WIDTH = __current_context.width()
    __HEIGHT = __current_context.height()


def paint_gl():
    """
    Stock PaintGL function from OpenGL that switches
    on the current mode to determine what action to
    perform on the current event.
    """
    if (__current_mode in [Mode.ADD, Mode.EDIT, Mode.MOVE, Mode.DELETE] and
        __current_event is None):
        raise InvalidStateError("Event must exist for ADD, EDIT, MOVE, " +
                                "and DELETE")

    if (__current_mode in [Mode.ADD, Mode.EDIT, Mode.MOVE, Mode.DELETE] and
        __current_points is None):
        raise InvalidStateError("Points must exist for ADD, EDIT, MOVE, " +
                                "and DELETE")

    if __current_mode is Mode.ADD or __current_mode is Mode.DELETE:
        # Note that drawing the points doesn't require a bounding box or
        # any special context, so delete just removes the element from
        # the point set, which will be redrawn here. This action
        # is the same as adding a point since we just draw what is in
        # the point set.
        draw_points(__current_points, Color.BLUE)
    elif __current_mode is Mode.EDIT:
        raise NotImplementedError("Drawing for EDIT not implemented.")
    elif __current_mode is Mode.MOVE:
        raise NotImplementedError("Drawing for MOVE not implemented.")
    elif __current_mode is Mode.DELETE:
        raise NotImplementedError("Drawing for DELETE not implemented.")


def __clamp_x(x):
    """
    X-coordinate clamping function that goes from mouse coordinates to
    OpenGL coordinates.

    @param x The x-coordinate to clamp.
    @returns The clamped x coordinate.
    """
    x_w = (x / (__WIDTH / 2.0) - 1.0)
    return x_w


def __clamp_y(y):
    """
    Y-coordinate clamping function that goes from mouse coordinates to
    OpenGL coordinates.

    @param y The y-coordinate to clamp.
    @returns The clamped y coordinate.
    """
    y_w = -1.0 * (y / (__HEIGHT / 2.0) - 1.0)
    return y_w


def draw_points(point_set, color):
    """
    Simple point drawing function.

    Given a coordinate (x, y), and a Color enum this
    function will draw the given point with the given
    color.

    @param point_set The PointSet to draw.
    @param color The Color Enum.
    """
    global __current_context

    if __current_context is None:
        raise InvalidStateError("Drawing context must be set before setting " +
                                "drawing mode")

    if not isinstance(color, Color):
        raise ValueError("Color must exist in the Color enumeration")

    ct = COLOR_TO_RGBA[color]

    glViewport(0, 0, __WIDTH, __HEIGHT)
    glPointSize(__current_points.point_size)


    glBegin(GL_POINTS)
    glColor4f(ct[0], ct[1], ct[2], ct[3])
    for point in point_set.points:
        glVertex3f(__clamp_x(point.x),
                   __clamp_y(point.y),
                   0.0)                 # Z is currently fixed to 0
    glEnd()