render-cursors.py

#!/usr/bin/env python3
#
# SVGSlice
#
# Released under the GNU General Public License, version 2.
# Email Lee Braiden of Digital Unleashed at lee.b@digitalunleashed.com
# with any questions, suggestions, patches, or general uncertainties
# regarding this software.
#

usageMsg = """You need to add a layer called "slices", and draw rectangles on it to represent the areas that should be saved as slices.  It helps when drawing these rectangles if you make them translucent.

If you name these slices using the "id" field of Inkscape's built-in XML editor, that name will be reflected in the slice filenames.

Please remember to HIDE the slices layer before exporting, so that the rectangles themselves are not drawn in the final image slices."""

# How it works:
#
# Basically, svgslice just parses an SVG file, looking for the tags that define
# the slices should be, and saves them in a list of rectangles.  Next, it generates
# an XHTML file, passing that out stdout to Inkscape.  This will be saved by inkscape
# under the name chosen in the save dialog.  Finally, it calls
# inkscape again to render each rectangle as a slice.
#
# Currently, nothing fancy is done to layout the XHTML file in a similar way to the
# original document, so the generated pages is essentially just a quick way to see
# all of the slices in once place, and perhaps a starting point for more layout work.
#

import argparse
import logging
from xml.sax import saxutils, make_parser, SAXParseException, handler, xmlreader
from xml.sax.handler import feature_namespaces
import os, sys, tempfile, shutil, subprocess
import re
from threading import Thread
from PIL import Image
import multiprocessing
import io


MODE_HOTSPOTS = ["hotspots"]
MODE_INVERT = ["invert"]
MODE_SHADOWS = ["shadows"]
MODE_SLICES = ["slices"]
RENDERERS = []
SCALE_PAIRS = [(1.25, "s1"), (1.50, "s2")]
SIZES = [24, 32, 48, 64, 96]
SVG_HOTSPOT_WORKING_COPY = "hotspot-working-copy.svg"
SVG_WORKING_COPY = "working-copy.svg"

debug = logging.debug
error = logging.error
info = logging.info
warning = logging.warning


def fatal(msg):
    logging.critical(msg)
    sys.exit(20)


def configure():
    parser = argparse.ArgumentParser()
    parser.add_argument("originalFilename", help="The input SVG file")
    parser.add_argument(
        "-d",
        "--debug",
        action="store_true",
        dest="debug",
        help="Enable extra debugging info.",
    )
    parser.add_argument(
        "-t",
        "--test",
        action="store_true",
        dest="testing",
        help="Test mode: leave temporary files for examination.",
    )
    parser.add_argument(
        "-p",
        "--sliceprefix",
        action="store",
        dest="sliceprefix",
        default="",
        help="Specifies the prefix to use for individual slice filenames.",
    )
    parser.add_argument(
        "-r",
        "--remove-shadows",
        action="store_true",
        dest="remove_shadows",
        help="Remove shadows the cursors have.",
    )
    parser.add_argument(
        "-o",
        "--hotspots",
        action="store_true",
        dest="hotspots",
        help="Produce hotspot images and hotspot datafiles.",
    )
    parser.add_argument(
        "-s",
        "--scales",
        action="store_true",
        dest="scales",
        help="Produce 125 and 150 percent (Large, and Extra Large) scaled versions of each image as well.",
    )
    parser.add_argument(
        "-m",
        "--min-canvas-size",
        action="store",
        type=int,
        dest="min_canvas_size",
        default=-1,
        help="Cursor canvas must be at least this big (defaults to -1).",
    )
    parser.add_argument(
        "-f",
        "--fps",
        action="store",
        type=int,
        dest="fps",
        default=60,
        help="Assume that all animated cursors have this FPS (defaults to 60).",
    )
    parser.add_argument(
        "-a",
        "--anicursorgen",
        action="store_true",
        dest="anicur",
        default=False,
        help="Assume that anicursorgen will be used to assemble cursors (xcursorgen is assumed by default).",
    )
    parser.add_argument(
        "-c",
        "--corner-align",
        action="store_true",
        dest="align_corner",
        default=False,
        help="Align cursors to the top-left corner (by default they are centered).",
    )
    parser.add_argument(
        "-i",
        "--invert",
        action="store_true",
        dest="invert",
        default=False,
        help="Invert colors (disabled by default).",
    )
    parser.add_argument(
        "-n",
        "--number-of-renderers",
        action="store",
        type=int,
        dest="number_of_renderers",
        default=1,
        help="Number of renderer instances run in parallel. Defaults to 1. Set to 0 for autodetection.",
    )

    options = parser.parse_args()

    # More detailed logging format if debug is enabled
    if options.debug:
        fmt = "[%(levelname)s] %(lineno)d:%(funcName)-s - %(message)s"
        level = logging.DEBUG
    else:
        fmt = "[%(levelname)s] %(message)s"
        level = logging.INFO
    logging.basicConfig(level=level, format=fmt)

    options.modes = get_modes(options)

    if not options.scales:
        del SCALE_PAIRS[:]

    if options.number_of_renderers <= 0:
        options.number_of_renderers = autodetect_threadcount()
    return options


def natural_sort(l):
    convert = lambda text: int(text) if text.isdigit() else text.lower()
    alphanum_key = lambda key: [convert(c) for c in re.split("([0-9]+)", key)]
    return sorted(l, key=alphanum_key)


def cleanup():
    global RENDERERS
    for inkscape, inkscape_stderr, inkscape_stderr_thread in RENDERERS:
        inkscape.communicate("quit\n".encode())
        del inkscape
        del inkscape_stderr_thread
        del inkscape_stderr
    del RENDERERS

    if SVG_WORKING_COPY != None and os.path.exists(SVG_WORKING_COPY):
        os.remove(SVG_WORKING_COPY)

    if SVG_HOTSPOT_WORKING_COPY != None and os.path.exists(SVG_HOTSPOT_WORKING_COPY):
        os.remove(SVG_HOTSPOT_WORKING_COPY)


def find_hotspot(hotfile):
    img = Image.open(hotfile)
    pixels = img.load()
    reddest = [-1, -1, -999999]
    for y in range(img.size[1]):
        for x in range(img.size[0]):
            redness = pixels[x, y][0] - pixels[x, y][1] - pixels[x, y][2]
            if redness > reddest[2]:
                reddest = [x, y, redness]
    return (reddest[0] + 1, reddest[1] + 1)


def cropalign(size, filename):
    img = Image.open(filename)
    content_dimensions = img.getbbox()
    if content_dimensions is None:
        content_dimensions = (0, 0, img.size[0], img.size[1])
    hcropped = content_dimensions[2] - content_dimensions[0]
    vcropped = content_dimensions[3] - content_dimensions[1]
    if hcropped > size or vcropped > size:
        if hcropped > size:
            left = (hcropped - size) / 2
            right = (hcropped - size) - left
        else:
            left = 0
            right = 0
        if vcropped > size:
            top = (vcropped - size) / 2
            bottom = (vcropped - size) - top
        else:
            top = 0
            bottom = 0
        content_dimensions = (
            content_dimensions[0] + left,
            content_dimensions[1] + top,
            content_dimensions[2] - right,
            content_dimensions[3] - bottom,
        )
        warn(
            f"{filename} is too big to be cleanly cropped to {size} ({hcropped}x{vcropped} at best)"
        )
        warn(
            "cropping to {}x{}!".format(
                content_dimensions[2] - content_dimensions[0],
                content_dimensions[3] - content_dimensions[1],
            )
        )

    if options.testing:
        img.save(filename + ".orig.png", "png")

    debug(
        f"{filename} content is {content_dimensions[0]} {content_dimensions[1]} {content_dimensions[2]} {content_dimensions[3]}"
    )

    cropimg = img.crop(
        (
            content_dimensions[0],
            content_dimensions[1],
            content_dimensions[2],
            content_dimensions[3],
        )
    )
    pixels = cropimg.load()
    if options.testing:
        cropimg.save(filename + ".crop.png", "png")
    if options.align_corner:
        expimg = cropimg.crop((0, 0, size, size))
        result = (content_dimensions[0], content_dimensions[1])
    else:
        hslack = size - cropimg.size[0]
        vslack = size - cropimg.size[1]
        left = hslack / 2
        top = vslack / 2
        expimg = cropimg.crop((-left, -top, size - left, size - top))
        result = (content_dimensions[0] - left, content_dimensions[1] - top)
    pixels = expimg.load()
    if options.invert:
        negative(expimg)
    expimg.save(filename, "png")
    del cropimg
    del img
    return result


def cropalign_hotspot(new_base, size, filename):
    if not new_base:
        return
    img = Image.open(filename)
    expimg = img.crop(
        (new_base[0], new_base[1], new_base[0] + size, new_base[1] + size)
    )
    pixels = expimg.load()
    expimg.save(filename, "png")
    del img


def negative(img):
    pixels = img.load()
    for y in range(0, img.size[1]):
        for x in range(0, img.size[0]):
            r, g, b, a = pixels[x, y]
            pixels[x, y] = (255 - r, 255 - g, 255 - b, a)


class SVGRect:
    """Manages a simple rectangular area, along with certain attributes such as a name"""

    def __init__(self, x1, y1, x2, y2, name=None):
        self.x1 = x1
        self.y1 = y1
        self.x2 = x2
        self.y2 = y2
        self.name = name
        debug(f"New SVGRect: {name}")

    def renderFromSVG(self, svgFName, slicename, skipped, roundrobin, hotsvgFName):
        def do_res(size, output, svgFName):
            global RENDERERS
            nonlocal skipped, roundrobin
            if os.path.exists(output):
                debug(f"{output} exists, skip rendering")
                skipped[output] = True
                return

            debug(f"rendering {output}")
            command = f"export-width:{size};"
            command += f" export-height:{size};"
            command += f" export-id:{self.name};"
            command += f" export-filename:{output};"
            command += f" export-do\n"
            debug(f"inkscape command: {command}")
            RENDERERS[roundrobin[0]][0].stdin.write(command.encode())

        pngsliceFName = f"{slicename}.png"
        hotsliceFName = f"{slicename}.hotspot.png"

        for i, size in enumerate(SIZES):
            subdir = f"bitmaps/{size}x{size}"

            if not os.path.exists(subdir):
                os.makedirs(subdir)

            relslice = f"{subdir}/{pngsliceFName}"
            do_res(size, relslice, svgFName)

            if options.hotspots:
                hotrelslice = f"{subdir}/{hotsliceFName}"
                do_res(size, hotrelslice, hotsvgFName)

            for scale in SCALE_PAIRS:
                subdir = f"bitmaps/{size}x{size}_{scale[1]}"
                relslice = f"{subdir}/{pngsliceFName}"

                if not os.path.exists(subdir):
                    os.makedirs(subdir)

                scaled_size = int(size * scale[0])
                do_res(scaled_size, relslice, svgFName)

                if options.hotspots:
                    hotrelslice = f"{subdir}/{hotsliceFName}"
                    do_res(scaled_size, hotrelslice, hotsvgFName)

            # This is not inside do_res() because we want each instance to work all scales in case scales are enabled,
            # otherwise instances that get mostly smallscale renders will finish up way before the others
            roundrobin[0] += 1
            if roundrobin[0] >= options.number_of_renderers:
                roundrobin[0] = 0


def get_next_size(index, current_size):
    if index % 2 == 0:
        # 24->32, 48->64, 96->128, 192->256
        return (current_size * 4) / 3
    else:
        # 32->48, 64->96, 128->192, 256->384
        return (current_size * 3) / 2


def get_csize(index, current_size):
    size = current_size
    if len(SCALE_PAIRS) > 0:
        size = get_next_size(index, size)
    return max(options.min_canvas_size, size)


def postprocess_slice(slicename, skipped):
    pngsliceFName = f"{slicename}.png"
    hotsliceFName = f"{slicename}.hotspot.png"

    for i, size in enumerate(SIZES):
        subdir = f"bitmaps/{size}x{size}"
        relslice = f"{subdir}/{pngsliceFName}"
        csize = get_csize(i, size)
        if relslice not in skipped:
            if options.hotspots:
                hotrelslice = f"{subdir}/{hotsliceFName}"
        for scale in SCALE_PAIRS:
            subdir = f"bitmaps/{size}x{size}_{scale[1]}"
            relslice = f"{subdir}/{pngsliceFName}"
            if relslice not in skipped:
                if options.hotspots:
                    hotrelslice = f"{subdir}/{hotsliceFName}"


def write_xcur(slicename):
    pngsliceFName = f"{slicename}.png"
    hotsliceFName = f"{slicename}.hotspot.png"

    framenum = -1
    if slicename[-5:].startswith("_"):
        try:
            framenum = int(slicename[-4:])
            slicename = slicename[:-5]
        except:
            pass

    # This relies on the fact that frame 1 is the first frame of an animation in the rect list
    # If that is not so, the *icongen input file will end up missing some of the lines
    if framenum == -1 or framenum == 1:
        mode = "wb"
    else:
        mode = "ab"
    if framenum == -1:
        fps_field = ""
    else:
        if options.anicur:
            # For anicursorgen use jiffies
            fps_field = " {}".format(int(60.0 / options.fps))
        else:
            # For xcursorgen use milliseconds
            fps_field = " {}".format(int(1000.0 / options.fps))

    xcur = {}
    xcur["s0"] = open(f"bitmaps/{slicename}.in", mode)
    if len(SCALE_PAIRS) > 0:
        xcur["s1"] = open(f"bitmaps/{slicename}.s1.in", mode)
        xcur["s2"] = open(f"bitmaps/{slicename}.s2.in", mode)

    for i, size in enumerate(SIZES):
        subdir = f"bitmaps/{size}x{size}"
        relslice = f"{subdir}/{pngsliceFName}"
        filename = f"{size}x{size}/{pngsliceFName}"
        hotrelslice = f"{subdir}/{hotsliceFName}"

        hot = find_hotspot(hotrelslice)
        csize = get_csize(i, size)

        xcur["s0"].write(f"{csize} {hot[0]} {hot[1]} {filename}{fps_field}\n")

        for scale in SCALE_PAIRS:
            subdir = f"bitmaps/{size}x{size}_{scale[1]}"
            relslice = f"{subdir}/{pngsliceFName}"
            filename = f"{size}x{size}/{scale[1]}"
            scaled_size = int(size * scale[0])
            hotrelslice = f"{subdir}/{hotsliceFName}"

            hot = find_hotspot(hotrelslice)

            xcur[scale[1]].write(f"{csize} {hot[0]} {hot[1]} {filename}{fps_field}\n")

    xcur["s0"].close()
    if len(SCALE_PAIRS) > 0:
        xcur["s1"].close()
        xcur["s2"].close()


def sort_file(filename):
    with open(filename, "rb") as src:
        contents = src.readlines()
    with open(filename, "wb") as dst:
        for line in natural_sort(contents):
            dst.write(line)


def sort_xcur(slicename, passed):
    pngsliceFName = f"{slicename}.png"

    framenum = -1
    if slicename[-5:].startswith("_"):
        try:
            framenum = int(slicename[-4:])
            slicename = slicename[:-5]
        except:
            pass
    if slicename in passed:
        return
    passed[slicename] = True

    sort_file("bitmaps/{slicename}.in")
    if len(SCALE_PAIRS) > 0:
        sort_file(f"bitmaps/{slicename}.s1.in")
        sort_file(f"bitmaps/{slicename}.s2.in")


def delete_hotspot(slicename):
    hotsliceFName = f"{slicename}.hotspot.png"

    for i, size in enumerate(SIZES):
        subdir = f"bitmaps/{size}x{size}"
        hotrelslice = f"{subdir}/{hotsliceFName}"
        if os.path.exists(hotrelslice):
            os.unlink(hotrelslice)
        for scale in SCALE_PAIRS:
            subdir = f"bitmaps/{size}x{size}_{scale[1]}"
            hotrelslice = f"{subdir}/{hotsliceFName}"
            if os.path.exists(hotrelslice):
                os.unlink(hotrelslice)


class SVGHandler(handler.ContentHandler):
    """Base class for SVG parsers"""

    def __init__(self):
        self.pageBounds = SVGRect(0, 0, 0, 0)

    def isFloat(self, stringVal):
        try:
            return (float(stringVal), True)[1]
        except (ValueError, TypeError) as e:
            return False

    def parseCoordinates(self, val):
        """Strips the units from a coordinate, and returns just the value."""

        if self.isFloat(val):
            return float(val)

        res = None
        supported_units = "px, pt, cm, mm, in, %"
        for unit in supported_units.split(", "):
            if val.endswith(unit):
                res = float(val.rstrip(unit))
                break

        if not res:
            fatal(
                f"Unsupported unit in value {val}. Valid units are {supported_units}."
            )

        return res

    def startElement_svg(self, name, attrs):
        """Callback hook which handles the start of an svg image"""

        width = attrs.get("width", None)
        height = attrs.get("height", None)
        self.pageBounds.x2 = self.parseCoordinates(width)
        self.pageBounds.y2 = self.parseCoordinates(height)

    def endElement(self, name):
        """General callback for the end of a tag"""
        debug(f'Ending element "{name}"')


class SVGLayerHandler(SVGHandler):
    """Parses an SVG file, extracing slicing rectangles from a "slices" layer"""

    def __init__(self):
        SVGHandler.__init__(self)
        self.svg_rects = []
        self.layer_nests = 0

    def inSlicesLayer(self):
        return self.layer_nests >= 1

    def add(self, rect):
        """Adds the given rect to the list of rectangles successfully parsed"""
        self.svg_rects.append(rect)

    def startElement_layer(self, name, attrs):
        """Callback hook for parsing layer elements

        Checks to see if we're starting to parse a slices layer, and sets the appropriate flags.  Otherwise, the layer will simply be ignored."""
        id = attrs["id"]
        debug(f'found layer: name="{name}" id="{id}"')
        if attrs.get("inkscape:groupmode", None) == "layer":
            if self.inSlicesLayer() or attrs["inkscape:label"] == "slices":
                self.layer_nests += 1

    def endElement_layer(self, name):
        """Callback for leaving a layer in the SVG file

        Just undoes any flags set previously."""
        debug(f'leaving layer: name="{name}"')
        if self.inSlicesLayer():
            self.layer_nests -= 1

    def startElement_rect(self, name, attrs):
        """Callback for parsing an SVG rectangle

        Checks if we're currently in a special "slices" layer using flags set by startElement_layer().  If we are, the current rectangle is considered to be a slice, and is added to the list of parsed
        rectangles.  Otherwise, it will be ignored."""

        if self.inSlicesLayer():
            x1 = self.parseCoordinates(attrs["x"])
            y1 = self.parseCoordinates(attrs["y"])
            x2 = self.parseCoordinates(attrs["width"]) + x1
            y2 = self.parseCoordinates(attrs["height"]) + y1
            name = attrs["id"]
            rect = SVGRect(x1, y1, x2, y2, name)
            self.add(rect)

    def startElement(self, name, attrs):
        """Generic hook for examining and/or parsing all SVG tags"""

        debug(f'Beginning element "{name}"')
        if name == "svg":
            self.startElement_svg(name, attrs)
        elif name == "g":
            # inkscape layers are groups, I guess, hence 'g'
            self.startElement_layer(name, attrs)
        elif name == "rect":
            self.startElement_rect(name, attrs)

    def endElement(self, name):
        """Generic hook called when the parser is leaving each SVG tag"""
        debug('Ending element "%s"' % name)
        if name == "g":
            self.endElement_layer(name)

    def generateXHTMLPage(self):
        """Generates an XHTML page for the SVG rectangles previously parsed."""
        write = sys.stdout.write
        write('<?xml version="1.0" encoding="UTF-8"?>\n')
        write(
            '<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "DTD/xhtml1-strict.dtd">\n'
        )
        write('<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">\n')
        write("    <head>\n")
        write("        <title>Sample SVGSlice Output</title>\n")
        write("    </head>\n")
        write("    <body>\n")
        write(
            "        <p>Sorry, SVGSlice's XHTML output is currently very basic.  Hopefully, it will serve as a quick way to preview all generated slices in your browser, and perhaps as a starting point for further layout work.  Feel free to write it and submit a patch to the author :)</p>\n"
        )

        write("        <p>")
        for rect in self.svg_rects:
            write(
                '            <img src="%s" alt="%s (please add real alternative text for this image)" longdesc="Please add a full description of this image" />\n'
                % (sliceprefix + rect.name + ".png", rect.name)
            )
        write("        </p>")

        write(
            '<p><a href="http://validator.w3.org/check?uri=referer"><img src="http://www.w3.org/Icons/valid-xhtml10" alt="Valid XHTML 1.0!" height="31" width="88" /></a></p>'
        )

        write("    </body>\n")
        write("</html>\n")


class SVGFilter(saxutils.XMLFilterBase):
    def __init__(self, upstream, downstream, mode, **kwargs):
        saxutils.XMLFilterBase.__init__(self, upstream)
        self._downstream = downstream
        self.mode = mode

    def startDocument(self):
        self.in_throwaway_layer_stack = [False]

    def startElement(self, localname, attrs):
        def modify_style(style, old_style, new_style=None):
            styles = style.split(";")
            new_styles = []
            if old_style is not None:
                match_to = old_style + ":"
            for s in styles:
                if len(s) > 0 and (old_style is None or not s.startswith(match_to)):
                    new_styles.append(s)
            if new_style is not None:
                new_styles.append(new_style)
            return ";".join(new_styles)

        dict = {}
        is_throwaway_layer = False
        is_slices = False
        is_hotspots = False
        is_shadows = False
        is_layer = False
        if localname == "g":
            for key, value in attrs.items():
                if key == "inkscape:label":
                    if value == "slices":
                        is_slices = True
                    elif value == "hotspots":
                        is_hotspots = True
                    elif value == "shadows":
                        is_shadows = True
                elif key == "inkscape:groupmode":
                    if value == "layer":
                        is_layer = True
        if MODE_SHADOWS in self.mode and is_shadows:
            # Only remove the shadows
            is_throwaway_layer = True
        elif MODE_HOTSPOTS in self.mode and not (is_hotspots or is_slices):
            # Remove all layers but hotspots and slices
            if localname == "g":
                is_throwaway_layer = True
        idict = {}
        idict.update(attrs)
        if "style" not in attrs.keys():
            idict["style"] = ""
        for key, value in idict.items():
            alocalname = key
            if alocalname == "style":
                had_style = True
            if alocalname == "style" and is_slices:
                # Make slices invisible. Do not check the mode, because there is
                # no circumstances where we *want* to render slices
                value = modify_style(value, "display", "display:none")
            if alocalname == "style" and is_hotspots:
                if MODE_HOTSPOTS in self.mode:
                    # Make hotspots visible in hotspots mode
                    value = modify_style(value, "display", "display:inline")
                else:
                    # Make hotspots invisible otherwise
                    value = modify_style(value, "display", "display:none")
            if (
                alocalname == "style"
                and MODE_INVERT in self.mode
                and is_layer
                and is_shadows
            ):
                value = modify_style(value, None, "filter:url(#InvertFilter)")
            dict[key] = value

        if self.in_throwaway_layer_stack[0] or is_throwaway_layer:
            self.in_throwaway_layer_stack.insert(0, True)
        else:
            self.in_throwaway_layer_stack.insert(0, False)
            attrs = xmlreader.AttributesImpl(dict)
            self._downstream.startElement(localname, attrs)

    def characters(self, content):
        if self.in_throwaway_layer_stack[0]:
            return
        self._downstream.characters(content)

    def endElement(self, localname):
        if self.in_throwaway_layer_stack.pop(0):
            return
        self._downstream.endElement(localname)


def filter_svg(input, output, mode):
    """filter_svg(input:file, output:file, mode)

    Parses the SVG input from the input stream.
    For mode == 'hotspots' it filters out all
    layers except for hotspots and slices. Also makes hotspots
    visible.
    For mode == 'shadows' it filters out the shadows layer.
    """

    mode_objs = [[m] for m in mode]
    if len(mode_objs) == 0:
        raise ValueError()

    output_gen = saxutils.XMLGenerator(output)
    parser = make_parser()
    filter = SVGFilter(parser, output_gen, mode_objs)
    filter.setFeature(handler.feature_namespaces, False)
    filter.setErrorHandler(handler.ErrorHandler())
    # This little I/O dance is here to ensure that SAX parser does not stash away
    # an open file descriptor for the input file, which would prevent us from unlinking it later
    with open(input, "rb") as inp:
        contents = inp.read()
    contents_io = io.BytesIO(contents)
    source_object = saxutils.prepare_input_source(contents_io)
    filter.parse(source_object)
    del filter
    del parser
    del output_gen


def autodetect_threadcount():
    try:
        count = multiprocessing.cpu_count()
    except NotImplementedError:
        count = 1
    return count


def get_modes(options):
    modes = ["slices"]
    if options.remove_shadows:
        modes.append("shadows")
    if options.invert:
        modes.append("invert")
    return modes


def parse_svg_file(filename):
    """Parse the SVG input file"""
    xml_parser = make_parser()
    xml_parser.setFeature(feature_namespaces, 0)
    handler = SVGLayerHandler()
    xml_parser.setContentHandler(handler)
    try:
        info(f"parsing {filename}")
        xml_parser.parse(filename)
    except SAXParseException as e:
        lineno = e.getLineNumber()
        colno = e.getColumnNumber()
        msg = e.getMessage()
        error(
            f"Error parsing {filename}, line:{lineno}, column:{colno}, message:{msg}.\n"
        )
        fatal(
            "If are seeing this within inkscape, it probably indicates a bug that should be reported."
        )

    if len(handler.svg_rects) == 0:
        fatal(
            """No slices were found in this SVG file.
Please refer to the documentation for guidance on how to use this SVGSlice.
As a quick summary:
"""
            + usageMsg
        )
    else:
        debug("Parsing successful.\n")

    # TODO why explicit delete?
    del xml_parser
    return handler


def stderr_reader(inkscape, inkscape_stderr):
    """Read from a file descriptor
    Used to read from inkscape process stderr"""
    while True:
        line = inkscape_stderr.readline()
        if line:
            line = line.rstrip("\n").rstrip("\r")
            print(f"inkscape STDERR> {line}")
            fatal(f"inkscape failed to render a slice. Aborting now")
        else:
            raise UnexpectedEndOfStream


def spawn_inkscape(number_of_renderers, filename):
    """ Spawn multiple instances of inkscape as for image rendering """
    info(f"spawning {number_of_renderers} inkscape instances")
    for i in range(number_of_renderers):
        proc = subprocess.Popen(
            ["inkscape", "--shell", filename],
            stdin=subprocess.PIPE,
            stdout=subprocess.PIPE,
            stderr=subprocess.PIPE,
        )
        if not proc:
            fatal("Failed to start Inkscape shell process")

        thread = Thread(target=stderr_reader, args=(proc, proc.stderr))
        RENDERERS.append([proc, proc.stderr, thread])


def render_pngs(svgLayerHandler, sliceprefix):
    debug("Loop through each slice rectangle, and render a PNG image for it")

    skipped = {}
    roundrobin = [0]

    for rect in svgLayerHandler.svg_rects:
        slicename = sliceprefix + rect.name
        rect.renderFromSVG(
            SVG_WORKING_COPY, slicename, skipped, roundrobin, SVG_HOTSPOT_WORKING_COPY
        )

    return skipped


def postprocess(svgLayerHandler, prefix, skipped, hotspots):
    for rect in svgLayerHandler.svg_rects:
        slicename = prefix + rect.name
        postprocess_slice(slicename, skipped)
        if options.hotspots:
            write_xcur(slicename)

    if options.hotspots:
        passed = {}
        for rect in svgLayerHandler.svg_rects:
            slicename = prefix + rect.name
            sort_xcur(slicename, passed)
            # if not option.testing:
            # 	delete_hotspot(slicename)


if __name__ == "__main__":
    options = configure()

    with open(SVG_WORKING_COPY, "wb") as output:
        filter_svg(options.originalFilename, output, options.modes)

    if options.hotspots:
        with open(SVG_HOTSPOT_WORKING_COPY, "wb") as output:
            filter_svg(options.originalFilename, output, ["hotspots"])

    try:
        spawn_inkscape(options.number_of_renderers, SVG_WORKING_COPY)
        svgLayerHandler = parse_svg_file(SVG_WORKING_COPY)
        skipped = render_pngs(svgLayerHandler, options.sliceprefix)
        postprocess(svgLayerHandler, options.sliceprefix, skipped, options.hotspots)
        debug("Slicing complete.")
    finally:
        cleanup()