Mirror images for RTL languages at build time.

build/android/gyp/mirror_images.py

Index: build/android/gyp/mirror_images.py
diff --git a/build/android/gyp/mirror_images.py b/build/android/gyp/mirror_images.py
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+#!/usr/bin/env python
+#
+# Copyright 2013 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""Mirrors (i.e. horizontally flips) images in the Android res folder for use
+in right-to-left (RTL) mode on Android.
+
+Only some images are mirrored, as determined by the config file, typically
+named mirror_images_config. The config file uses python syntax to define
+two lists of image names: images_to_mirror and images_not_to_mirror. Images in
+images_to_mirror will be mirrored by this tool. To ensure every image has been
+considered for mirroring, the remaining images must be listed in
+images_not_to_mirror.
+
+Mirrorable images include directional images (e.g. back and forward buttons) and
+asymmetric UI elements (e.g. a left-to-right fade image). Non-mirrorable images
+include images with text (e.g. the Chrome logo), symmetric images (e.g. a star
+or X button), and images whose asymmetry is not critical to their meaning. Most
+images do not need to be mirrored.
+
+Example mirror_images_config:
+
+  images_to_mirror = ['back.png', 'forward.png', 'left_to_right_fade.png']
+  images_not_to_mirror = ['star.png', 'chrome_logo.png', 'blank_page.png']
+
+Source images are taken from input_dir/res/drawable-* folders, and the
+generated images are saved into output_dir/res/drawable-ldrtl-* folders. For
+example: input_dir/res/drawable-hdpi/back.png would be mirrored into
+output_dir/res/drawable-ldrtl-hdpi/back.png.
+"""
+
+import errno
+import multiprocessing.pool
+import optparse
+import os
+import subprocess
+import sys
+
+from util import build_utils
+
+BUILD_ANDROID_DIR = os.path.join(os.path.dirname(__file__), '..')
+sys.path.append(BUILD_ANDROID_DIR)
+
+from pylib import constants
+
+
+class Image(object):
+  """Represents an image in the Android res directory."""
+
+  def __init__(self, drawable_dir, name):
+    # The image's directory, e.g. drawable-hdpi
+    self.drawable_dir = drawable_dir
+    # The image's filename, e.g. star.png
+    self.name = name
+
+
+class ConfigError(Exception):
+  """Error raised when images can't be mirrored because of problems with the
+  config file."""
+
+  def __init__(self, error_messages):
+    # A list of strings describing the errors in the config file.
+    self.error_messages = error_messages
+
+
+class Project(object):
+  """This class knows how to read the config file and mirror images in an
+  Android project."""
+
+  def __init__(self, config_file, input_res_dir, output_res_dir):
+    """Args:
+      config_file: The config file specifying which images will be mirrored.
+      input_res_dir: The directory containing source images to be mirrored.
+      output_res_dir: The directory into which mirrored images can be saved.
+    """
+    self.config_file = config_file
+    self.input_res_dir = input_res_dir
+    self.output_res_dir = output_res_dir
+
+    # List of names of images that will be mirrored, from config file.
+    self.images_to_mirror = None
+    # List of names of images that will not be mirrored, from config file.
+    self.images_not_to_mirror = None
+    # List of all images found in res/drawable* directories.
+    self.images = None
+
+  def mirror_images(self):
+    """Mirrors images in the project according to the configuration.
+
+    If the project configuration contains any errors, this will raise a
+    ConfigError exception containing a list of errors that must be addressed
+    manually before any images can be mirrored.
+    """
+    self._read_config_file()
+    self._read_drawable_dirs()
+    self._verify_config()
+    self._mirror_images()
+
+  def _read_config_file(self):
+    """Reads the lists of images that should and should not be mirrored from the
+    config file.
+    """
+    exec_env = {}
+    execfile(self.config_file, exec_env)
+    self.images_to_mirror = exec_env.get('images_to_mirror')
+    self.images_not_to_mirror = exec_env.get('images_not_to_mirror')
+    errors = []
+    self._verify_config_list_well_formed(self.images_to_mirror,
+        'images_to_mirror', errors)
+    self._verify_config_list_well_formed(self.images_not_to_mirror,
+        'images_not_to_mirror', errors)
+    if errors:
+      raise ConfigError(errors)
+
+  def _verify_config_list_well_formed(self, config_list, list_name, errors):
+    """Checks that config_list is a list of strings. If not, appends error
+    messages to errors."""
+    if type(config_list) != list:
+      errors.append('The config file must contain a list named ' + list_name)
+    else:
+      for item in config_list:
+        if not isinstance(item, basestring):
+          errors.append('List {0} contains a non-string item: {1}'
+              .format(list_name, item))
+
+  def _read_drawable_dirs(self):
+    """Gets the list of images in the input drawable directories."""
+    self.images = []
+
+    for dir_name in os.listdir(self.input_res_dir):
+      dir_components = dir_name.split('-')
+      if dir_components[0] != 'drawable' or 'ldrtl' in dir_components[1:]:
+        continue
+      dir_path = os.path.join(self.input_res_dir, dir_name)
+      if not os.path.isdir(dir_path):
+        continue
+
+      for image_name in os.listdir(dir_path):
+        if image_name.endswith('.png'):
+          self.images.append(Image(dir_name, image_name))
+
+  def _verify_config(self):
+    """Checks the config file for errors. Raises a ConfigError if errors are
+    found."""
+    errors = []
+
+    # Ensure images_to_mirror and images_not_to_mirror are sorted with no
+    # duplicates.
+    for l in self.images_to_mirror, self.images_not_to_mirror:
+      for i in range(len(l) - 1):
+        if l[i + 1] == l[i]:
+          errors.append(l[i + 1] + ' is listed multiple times')
+        elif l[i + 1] < l[i]:
+          errors.append(l[i + 1] + ' is not in sorted order')
+
+    # Ensure no overlap between images_to_mirror and images_not_to_mirror.
+    overlap = set(self.images_to_mirror).intersection(self.images_not_to_mirror)
+    for item in sorted(overlap):
+      errors.append(item + ' appears in both lists.')
+
+    # Ensure all images in res/drawable* folders are listed in config file.
+    images_in_config = set(self.images_to_mirror + self.images_not_to_mirror)
+    images_in_res_dir = [i.name for i in self.images]
+    images_missing_from_config = set(images_in_res_dir).difference(
+        images_in_config)
+    for image_name in sorted(images_missing_from_config):
+      errors.append(image_name + ' exists in a res/drawable* folder but is not '
+          'listed in the config file. Update the config file to specify '
+          'whether this image should be mirrored for right-to-left layouts (or '
+          'delete the image).')
+
+    # Ensure only images in res/drawable* folders are listed in config file.
+    images_not_in_res_dir = set(images_in_config).difference(
+        images_in_res_dir)
+    for image_name in sorted(images_not_in_res_dir):
+      errors.append(image_name + ' is listed in the config file, but does not '
+          'exist in any res/drawable* folders. Remove this image name from the '
+          'config file (or add the image to a drawable folder).')
+
+    if errors:
+      raise ConfigError(errors)
+
+  def _mirror_image(self, image):
+    ltr_path = os.path.join(self.input_res_dir, image.drawable_dir, image.name)
+    rtl_path = os.path.join(self.output_res_dir,
+                            get_rtl_dir(image.drawable_dir), image.name)
+    build_utils.MakeDirectory(os.path.dirname(rtl_path))
+    mirror_image(ltr_path, rtl_path)
+
+  def _mirror_images(self):
+    pool = multiprocessing.pool.ThreadPool()
+    images_to_mirror = [i for i in self.images if
+                        i.name in self.images_to_mirror]
+    pool.map(self._mirror_image, images_to_mirror)
+
+
+def get_rtl_dir(drawable_dir_ltr):
+  """Returns the RTL drawable directory corresponding to drawable_dir_ltr.
+
+  Example:
+    drawable-hdpi -> drawable-ldrtl-hdpi
+  """
+  dir_components = drawable_dir_ltr.split('-')
+  assert 'ldrtl' not in dir_components
+  # ldrtl is always the first qualifier, as long as mobile country code or
+  # language and region aren't used as qualifiers:
+  # http://developer.android.com/guide/topics/resources/providing-resources.html
+  dir_components.insert(1, 'ldrtl')
+  return '-'.join(dir_components)
+
+
+def mirror_image(src_path, dst_path):
+  """Mirrors a single image horizontally. 9-patches are treated specially: the
+  left and right edges of a 9-patch are not mirrored.
+
+  Args:
+    src_path: The image to be mirrored.
+    dst_path: The path where the mirrored image will be saved.
+  """
+  try:
+    if src_path.endswith('.9.png'):
+      build_utils.CheckOutput(['convert', src_path,
+                               '(', '+clone', '-flop', '-shave', '1x0', ')',
+                               '-compose', 'Copy',
+                               '-geometry', '+1+0',
+                               '-composite', dst_path])
+    else:
+      build_utils.CheckOutput(['convert', '-flop', src_path, dst_path])
+  except OSError as e:
+    if e.errno == errno.ENOENT:
+      raise Exception('Executable "convert" (from the imagemagick package) not '
+          'found. Run build/install-build-deps-android.sh and ensure '
+          'that "convert" is on your path.')
+    raise
+
+
+def parse_args(args=None):
+  parser = optparse.OptionParser()
+  parser.add_option('--config-file', help='Configuration file specifying which '
+      'images should be mirrored')
+  parser.add_option('--input-res-dir', help='The res folder containing the '
+      'source images.')
+  parser.add_option('--output-res-dir', help='The res folder into which '
+      'mirrored images will be saved.')
+
+  if args is None:
+    args = sys.argv[1:]
+  options, args = parser.parse_args(args)
+
+  # Check that required options have been provided.
+  required_options = ('config_file', 'input_res_dir', 'output_res_dir')
+  build_utils.CheckOptions(options, parser, required=required_options)
+
+  return options
+
+
+def main(args=None):
+  options = parse_args(args)
+  project = Project(options.config_file, options.input_res_dir,
+                    options.output_res_dir)
+  try:
+    project.mirror_images()
+  except ConfigError as e:
+    sys.stderr.write('\nFailed to mirror images for RTL layouts.\n')
+    sys.stderr.write('{0} error(s) in config file {1}:\n'.format(
+        len(e.error_messages),
+        os.path.relpath(options.config_file, constants.DIR_SOURCE_ROOT)))
+    for error_message in e.error_messages:
+      sys.stderr.write(' - {0}\n'.format(error_message))
+    sys.stderr.write('For more information on mirroring images, read the '
+        'header comment in build/android/gyp/mirror_images.py.\n')
+    sys.exit(1)
+
+
+if __name__ == '__main__':
+  main()