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418 lines
14 KiB
Python
418 lines
14 KiB
Python
# coding: utf8
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# WeasyPrint converts web documents (HTML, CSS, ...) to PDF.
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# Copyright (C) 2011 Simon Sapin
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#
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU Affero General Public License as
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# published by the Free Software Foundation, either version 3 of the
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# License, or (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU Affero General Public License for more details.
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#
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# You should have received a copy of the GNU Affero General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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"""
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Module drawing documents.
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"""
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from __future__ import division
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import contextlib
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import urllib
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import cairo
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from StringIO import StringIO
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from .formatting_structure import boxes
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from .css.values import get_percentage_value
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from .utils import urlopen
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SUPPORTED_IMAGES = ['image/png', 'image/gif', 'image/jpeg', 'image/bmp']
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def get_image_surface_from_uri(uri):
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"""Get a :class:`cairo.ImageSurface`` from an image URI."""
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file_like, mime_type, _charset = urlopen(uri)
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# TODO: implement image type sniffing?
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# http://www.w3.org/TR/html5/fetching-resources.html#content-type-sniffing:-image
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if mime_type in SUPPORTED_IMAGES:
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if mime_type == "image/png":
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image = file_like
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else:
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from PIL import Image
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pil_image = Image.open(StringIO(file_like.read()))
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image = StringIO()
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pil_image = pil_image.convert('RGBA')
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pil_image.save(image, "PNG")
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image.seek(0)
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return cairo.ImageSurface.create_from_png(image)
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class CairoContext(cairo.Context):
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"""A ``cairo.Context`` with a few more helper methods."""
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def set_source_colorvalue(self, color):
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"""Set the source pattern from a ``cssutils.ColorValue`` object."""
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self.set_source_rgba(
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color.red / 255., color.green / 255., color.blue / 255.,
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color.alpha)
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@contextlib.contextmanager
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def stacked(self):
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"""Save and restore the context when used with the ``with`` keyword."""
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self.save()
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try:
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yield
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finally:
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self.restore()
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def draw_page(page, context):
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"""Draw the given PageBox to a Cairo context.
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The context should be scaled so that lengths are in CSS pixels.
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"""
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draw_page_background(context, page)
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draw_border(context, page)
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draw_box(context, page.root_box)
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def draw_box(context, box):
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"""Draw a ``box`` on ``context``."""
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if box.style.visibility == 'visible':
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if has_background(box):
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draw_background(context, box)
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draw_border(context, box)
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marker_box = getattr(box, 'outside_list_marker', None)
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if marker_box:
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draw_box(context, marker_box)
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if isinstance(box, boxes.TextBox):
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draw_text(context, box)
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return
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if isinstance(box, boxes.ReplacedBox):
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draw_replacedbox(context, box)
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if isinstance(box, boxes.TableBox):
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for child in box.column_groups:
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draw_box(context, child)
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if isinstance(box, boxes.ParentBox):
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for child in box.children:
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draw_box(context, child)
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def has_background(box):
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"""Return whether the given box has any background."""
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return box.style.background_color.alpha > 0 or \
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box.style.background_image != 'none'
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def draw_page_background(context, page):
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"""Draw the backgrounds for the page box (from @page style) and for the
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page area (from the root element).
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If the root element is "html" and has no background, the page area’s
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background is taken from its "body" child.
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In both cases the background position is the same as if it was drawn on
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the element.
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See http://www.w3.org/TR/CSS21/colors.html#background
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"""
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# TODO: this one should have its origin at (0, 0), not the border box
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# of the page.
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# TODO: more tests for this, see
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# http://www.w3.org/TR/css3-page/#page-properties
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draw_background(context, page, clip=False)
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if has_background(page.root_box):
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draw_background(context, page.root_box, clip=False)
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elif page.root_box.element_tag.lower() == 'html':
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for child in page.root_box.children:
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if child.element_tag.lower() == 'body':
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# This must be drawn now, before anything on the root element.
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draw_background(context, child, clip=False)
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def draw_background(context, box, clip=True):
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"""Draw the box background color and image to a ``cairo.Context``."""
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if getattr(box, 'background_drawn', False):
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return
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box.background_drawn = True
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if not has_background(box):
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return
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with context.stacked():
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bg_x = box.border_box_x()
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bg_y = box.border_box_y()
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bg_width = box.border_width()
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bg_height = box.border_height()
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bg_attachement = box.style.background_attachment
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if bg_attachement == 'fixed':
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# There should not be any clip yet
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x1, y1, x2, y2 = context.clip_extents()
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page_width = x2 - x1
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page_height = y2 - y1
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if clip:
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context.rectangle(bg_x, bg_y, bg_width, bg_height)
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context.clip()
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# Background color
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bg_color = box.style.background_color
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if bg_color.alpha > 0:
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context.set_source_colorvalue(bg_color)
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context.paint()
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if bg_attachement == 'scroll':
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# Change coordinates to make the rest easier.
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context.translate(bg_x, bg_y)
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else:
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assert bg_attachement == 'fixed'
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bg_width = page_width
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bg_height = page_height
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# Background image
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bg_image = box.style.background_image
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if bg_image == 'none':
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return
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surface = box.document.get_image_surface_from_uri(bg_image)
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if surface is None:
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return
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image_width = surface.get_width()
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image_height = surface.get_height()
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bg_position = box.style.background_position
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bg_position_x, bg_position_y = absolute_background_position(
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bg_position, (bg_width, bg_height), (image_width, image_height))
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context.translate(bg_position_x, bg_position_y)
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bg_repeat = box.style.background_repeat
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if bg_repeat != 'repeat':
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# Get the current clip rectangle
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clip_x1, clip_y1, clip_x2, clip_y2 = context.clip_extents()
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clip_width = clip_x2 - clip_x1
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clip_height = clip_y2 - clip_y1
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if bg_repeat in ('no-repeat', 'repeat-x'):
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# Limit the drawn area vertically
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clip_y1 = 0 # because of the last context.translate()
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clip_height = image_height
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if bg_repeat in ('no-repeat', 'repeat-y'):
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# Limit the drawn area horizontally
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clip_x1 = 0 # because of the last context.translate()
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clip_width = image_width
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# Second clip for the background image
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context.rectangle(clip_x1, clip_y1, clip_width, clip_height)
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context.clip()
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context.set_source_surface(surface)
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context.get_source().set_extend(cairo.EXTEND_REPEAT)
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context.paint()
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def absolute_background_position(css_values, bg_dimensions, image_dimensions):
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"""Return the background's ``position_x, position_y`` in pixels.
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http://www.w3.org/TR/CSS21/colors.html#propdef-background-position
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:param css_values: a list of one or two cssutils Value objects.
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:param bg_dimensions: ``width, height`` of the background positionning area
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:param image_dimensions: ``width, height`` of the background image
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"""
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values = list(css_values)
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if len(css_values) == 1:
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values.append('center')
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else:
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assert len(css_values) == 2
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if values[1] in ('left', 'right') or values[0] in ('top', 'bottom'):
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values.reverse()
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# Order is now [horizontal, vertical]
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kw_to_percentage = dict(top=0, left=0, center=50, bottom=100, right=100)
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for value, bg_dimension, image_dimension in zip(
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values, bg_dimensions, image_dimensions):
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percentage = kw_to_percentage.get(value, get_percentage_value(value))
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if percentage is not None:
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yield (bg_dimension - image_dimension) * percentage / 100.
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else:
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yield value
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def get_rectangle_edges(x, y, width, height):
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"""Return the 4 edges of a rectangle as a list.
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Edges are in clock-wise order, starting from the top.
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Each edge is returned as ``(start_point, end_point)`` and each point
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as ``(x, y)`` coordinates.
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"""
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# In clock-wise order, starting on top left
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corners = [
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(x, y),
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(x + width, y),
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(x + width, y + height),
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(x, y + height)]
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# clock-wise order, starting on top right
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shifted_corners = corners[1:] + corners[:1]
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return zip(corners, shifted_corners)
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def draw_border(context, box):
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"""Draw the box border to a ``cairo.Context``."""
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if all(box.style['border_%s_width' % side] == 0
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for side in ['top', 'right', 'bottom', 'left']):
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# No border, return early.
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return
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for side, x_offset, y_offset, border_edge, padding_edge in zip(
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['top', 'right', 'bottom', 'left'],
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[0, -1, 0, 1],
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[1, 0, -1, 0],
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get_rectangle_edges(
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box.border_box_x(), box.border_box_y(),
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box.border_width(), box.border_height(),
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),
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get_rectangle_edges(
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box.padding_box_x(), box.padding_box_y(),
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box.padding_width(), box.padding_height(),
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),
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):
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width = box.style['border_%s_width' % side]
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if width == 0:
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continue
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color = box.style['border_%s_color' % side]
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if color.alpha == 0:
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continue
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style = box.style['border_%s_style' % side]
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with context.stacked():
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"""
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Both edges form a trapezoid. This is the top one:
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+---------------+
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\ /
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=================
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\ /
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+-------+
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We clip on its outline on draw on the big line on the middle.
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"""
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# I find that anti-aliasing does not look good on borders.
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context.set_antialias(cairo.ANTIALIAS_NONE)
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# TODO: implement other styles.
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if not style in ['dotted', 'dashed']:
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border_start, border_stop = border_edge
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padding_start, padding_stop = padding_edge
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# Move to one of the Trapezoid’s corner
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context.move_to(*border_start)
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for point in [border_stop, padding_stop,
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padding_start, border_start]:
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context.line_to(*point)
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context.clip()
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elif style == 'dotted':
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# TODO: find a way to make a real dotted border
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context.set_dash([width], 0)
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elif style == 'dashed':
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# TODO: find a way to make a real dashed border
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context.set_dash([4 * width], 0)
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(x1, y1), (x2, y2) = border_edge
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offset = width / 2
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x_offset *= offset
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y_offset *= offset
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x1 += x_offset
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x2 += x_offset
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y1 += y_offset
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y2 += y_offset
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context.move_to(x1, y1)
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context.line_to(x2, y2)
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context.set_source_colorvalue(color)
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context.set_line_width(width)
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context.stroke()
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def draw_replacedbox(context, box):
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"""Draw the given :class:`boxes.ReplacedBox` to a ``cairo.context``."""
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x, y = box.padding_box_x(), box.padding_box_y()
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width, height = box.width, box.height
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with context.stacked():
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context.translate(x, y)
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context.rectangle(0, 0, width, height)
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context.clip()
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scale_width = width / box.replacement.intrinsic_width()
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scale_height = height / box.replacement.intrinsic_height()
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context.scale(scale_width, scale_height)
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box.replacement.draw(context)
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def draw_text(context, textbox):
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"""Draw ``textbox`` to a ``cairo.Context`` from ``PangoCairo.Context``."""
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# Pango crashes with font-size: 0
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assert textbox.style.font_size
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context.move_to(textbox.position_x, textbox.position_y + textbox.baseline)
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context.set_source_colorvalue(textbox.style.color)
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textbox.show_line(context)
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values = textbox.style.text_decoration
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for value in values:
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if value == 'overline':
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draw_overline(context, textbox)
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elif value == 'underline':
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draw_underline(context, textbox)
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elif value == 'line-through':
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draw_line_through(context, textbox)
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def draw_overline(context, textbox):
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"""Draw overline of ``textbox`` to a ``cairo.Context``."""
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font_size = textbox.style.font_size
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position_y = textbox.baseline + textbox.position_y - (font_size * 0.15)
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draw_text_decoration(context, position_y, textbox)
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def draw_underline(context, textbox):
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"""Draw underline of ``textbox`` to a ``cairo.Context``."""
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font_size = textbox.style.font_size
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position_y = textbox.baseline + textbox.position_y + (font_size * 0.15)
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draw_text_decoration(context, position_y, textbox)
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def draw_line_through(context, textbox):
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"""Draw line-through of ``textbox`` to a ``cairo.Context``."""
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position_y = textbox.position_y + (textbox.height * 0.5)
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draw_text_decoration(context, position_y, textbox)
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def draw_text_decoration(context, position_y, textbox):
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"""Draw text-decoration of ``textbox`` to a ``cairo.Context``."""
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with context.stacked():
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context.set_source_colorvalue(textbox.style.color)
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context.set_line_width(1) # TODO: make this proportional to font_size?
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context.move_to(textbox.position_x, position_y)
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context.rel_line_to(textbox.width, 0)
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context.stroke()
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