"""
Helper funtions and classes for Cairo (drawing engine used by the canvas).
"""

from math import pi
import cairo

def text_extents(cr, text, font=None, multiline=False, padding=1):
    """
    Simple way to determine the size of a piece of text.
    """
    if not text:
        return 0, 0
    if font:
        cr.save()
        text_set_font(cr, font)

    if multiline:
        width, height = 0, 0
        for line in text.split('\n'):
            x_bear, y_bear, w, h, x_adv, y_adv = cr.text_extents(line)
            width = max(width, w)
            height += h + padding
    else:
        x_bear, y_bear, width, height, x_adv, y_adv = cr.text_extents(text)
        #width, height = width + x_bearing, height + y_bearing

    if font:
        cr.restore()
    return width, height


def text_center(cr, x, y, text):
    text_align(cr, x, y, text, align_x=0, align_y=0)

def text_align(cr, x, y, text, align_x=0, align_y=0, padding_x=0, padding_y=0):
    """
    Draw text using (x, y) as center.
    x    - center x
    y    - center y
    text - text to print (utf8)
    align_x - -1 (top), 0 (middle), 1 (bottom)
    align_y - -1 (left), 0 (center), 1 (right)
    padding_x - padding (extra offset), always > 0
    padding_y - padding (extra offset), always > 0
    """
    if not text:
        return

    x_bear, y_bear, w, h, x_adv, y_adv = cr.text_extents(text)
    if align_x == 0:
        x = 0.5 - (w / 2 + x_bear) + x
    elif align_x < 0:
        x = - (w + x_bear) + x - padding_x
    else:
        x = x + padding_x
    if align_y == 0:
        y = 0.5 - (h / 2 + y_bear) + y
    elif align_y < 0:
        y = - (h + y_bear) + y - padding_y
    else:
        y = -y_bear + y + padding_y
    cr.move_to(x, y)
    cr.show_text(text)

def text_multiline(cr, x, y, text, padding=1):
    """
    Draw a string of text with embedded newlines.
    cr - cairo context
    x - leftmost x
    y - topmost y
    text - text to draw
    padding - additional padding between lines.
    """
    if not text: return
    #cr.move_to(x, y)
    for line in text.split('\n'):
        x_bear, y_bear, w, h, x_adv, y_adv = cr.text_extents(text)
        cr.move_to(x, y)
        cr.show_text(line)
        y += h + padding

def text_set_font(cr, font):
    """Set the font from a string. E.g. 'sans 10' or 'sans italic bold 12'
    only restriction is that the font name should be the first option and
    the font size as last argument
    """
    font = font.split()
    cr.select_font_face(font[0],
                        'italic' in font and cairo.FONT_SLANT_ITALIC \
                                        or cairo.FONT_SLANT_NORMAL,
                        'bold' in font and cairo.FONT_WEIGHT_BOLD \
                                        or cairo.FONT_WEIGHT_NORMAL)
    cr.set_font_size(int(font[-1]))


def path_ellipse (cr, x, y, width, height, angle=0):
    """Draw an ellipse.
    x      - center x
    y      - center y
    width  - width of ellipse  (in x direction when angle=0)
    height - height of ellipse (in y direction when angle=0)
    angle  - angle in radians to rotate, clockwise
    """
    cr.save()
    cr.translate (x, y)
    cr.rotate (angle)
    cr.scale (width / 2.0, height / 2.0)
    cr.move_to(1.0, 0.0)
    cr.arc (0.0, 0.0, 1.0, 0.0, 2.0 * pi)
    cr.restore()


# vim:sw=4:et