Create fonts.xml module for adding fonts.xml to system/etc

Previously, we used PRODUCT_COPY_FILES. However, that does not allow
overriding the file to use a different one on a per-device basis.
This change migrates the logic to using a BUILD_PREBUILT module
called fonts.xml.
To add additional fonts, the add_additional_fonts.py script has been
added. If ADDITIONAL_FONTS_FILE is defined, add_additional_fonts.py
is run and generates a new version of fonts.xml that contains the
content of ADDITIONAL_FONTS_FILE added where
"<!-- fallback fonts -->" is added.

Bug: 36855735
Bug: 37997769
Test: manual. built multiple devices and verified that the correct
versions of fonts.xml were showing.

Change-Id: I8308f0cb3068274bca5ebd25a38cc023babbd69d

data/fonts/Android.mk

@@ -81,6 +81,33 @@ $(foreach f, $(font_src_files), $(call build-one-font-module, $(f)))
 build-one-font-module :=
 font_src_files :=
 
+################################
+# Copies the font configuration file into system/etc for the product as fonts.xml.
+# In the case where $(ADDITIONAL_FONTS_FILE) is defined, the content of $(ADDITIONAL_FONTS_FILE)
+# is added to the $(AOSP_FONTS_FILE).
+include $(CLEAR_VARS)
+
+LOCAL_MODULE := fonts.xml
+LOCAL_MODULE_CLASS := ETC
+
+AOSP_FONTS_FILE := frameworks/base/data/fonts/fonts.xml
+
+ifdef ADDITIONAL_FONTS_FILE
+ADDITIONAL_FONTS_SCRIPT := frameworks/base/tools/fonts/add_additional_fonts.py
+ADD_ADDITIONAL_FONTS := $(local-generated-sources-dir)/fonts.xml
+
+$(ADD_ADDITIONAL_FONTS): PRIVATE_SCRIPT := $(ADDITIONAL_FONTS_SCRIPT)
+$(ADD_ADDITIONAL_FONTS): PRIVATE_ADDITIONAL_FONTS_FILE := $(ADDITIONAL_FONTS_FILE)
+$(ADD_ADDITIONAL_FONTS): $(ADDITIONAL_FONTS_SCRIPT) $(AOSP_FONTS_FILE) $(ADDITIONAL_FONTS_FILE)
+	rm -f $@
+	python $(PRIVATE_SCRIPT) $@ $(PRIVATE_ADDITIONAL_FONTS_FILE)
+else
+ADD_ADDITIONAL_FONTS := $(AOSP_FONTS_FILE)
+endif
+
+LOCAL_PREBUILT_MODULE_FILE := $(ADD_ADDITIONAL_FONTS)
+
+include $(BUILD_PREBUILT)
 
 # Run sanity tests on fonts on checkbuild
 checkbuild: fontchain_lint

data/fonts/fonts.mk

@@ -14,9 +14,7 @@
 
 # Warning: this is actually a product definition, to be inherited from
 
-PRODUCT_COPY_FILES := \
-    frameworks/base/data/fonts/fonts.xml:$(TARGET_COPY_OUT_SYSTEM)/etc/fonts.xml
-
 PRODUCT_PACKAGES := \
     DroidSansMono.ttf \
-    AndroidClock.ttf
+    AndroidClock.ttf \
+    fonts.xml

tools/fonts/add_additional_fonts.py

@@ -0,0 +1,44 @@
+#!/usr/bin/env python
+#
+# Copyright (C) 2017 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+import sys
+
+def main(argv):
+    original_file = 'frameworks/base/data/fonts/fonts.xml'
+
+    if len(argv) == 3:
+        output_file_path = argv[1]
+        override_file_path = argv[2]
+    else:
+        raise ValueError("Wrong number of arguments %s" % len(argv))
+
+    fallbackPlaceholderFound = False
+    with open(original_file, 'r') as input_file:
+        with open(output_file_path, 'w') as output_file:
+            for line in input_file:
+                # If we've found the spot to add additional fonts, add them.
+                if line.strip() == '<!-- fallback fonts -->':
+                    fallbackPlaceholderFound = True
+                    with open(override_file_path) as override_file:
+                        for override_line in override_file:
+                            output_file.write(override_line)
+                output_file.write(line)
+    if not fallbackPlaceholderFound:
+        raise ValueError('<!-- fallback fonts --> not found in source file: %s' % original_file)
+
+if __name__ == '__main__':
+    main(sys.argv)