tree: a303d468ebd73d2ad062fe90e9d96f2785958677 [path history] [tgz]
  1. OWNERS
  2. README.md
  3. chrome-icu-93.0.4554.0_rc-r1.ebuild
  4. chrome-icu-9999.ebuild
chromeos-base/chrome-icu/README.md

The Chrome ICU package

This ebuild builds and installs the icu package in chrome so that it can be used in Chrome OS. Compared with the vanilla ICU library, it is customised for Chrome so there are some missing functionality and encoding (e.g. ISO-2022-CN and ISO-2022-KR). But it should be powerful enough for most usages. (It supports the i18n of Chrome!)

Why chrome-icu?

The biggest reason is to save resources. Chrome-icu saves,

  1. 10MB of rootfs disk space due to sharing the icu data.
  2. Up to 10MB of RAM because of sharing the icu data.
  3. Maintaining effort in Chrome OS (icu needs regular major uprev every 6 months and small bug fixes from time to time).

How to use it?

Please give us a heads-up if you want to use it. This is because chrome-icu is currently a static library, so linking it will non-trivially increase the disk space. And if the users of chrome-icu become more and more, we will spend the effort to make it into a shared library. (This will not affect your usage, please see the tracker.)

  1. Add chrome-icu as a dependency in your ebuild.
  2. Link icui18n-chrome and icuuc-chrome libraries.
  3. Add header paths ${sysroot}/usr/include/icu-chrome/common and ${sysroot}/usr/include/icu-chrome/i18n.
  4. If some headers are missing, you can add them to here.
  5. At run time, load the icu data file from /opt/google/chrome/icudtl.dat. You can follow the example here.

TODO

  1. We should consider setting up a CQ tryjob for chrome-icu, although this has become not very urgent after we only configure the icu package in compiling chrome-icu.
  2. We should consider having a build-chrome.eclass and avoid the duplication between chromeos-chrome.ebuild and chrome-icu.ebuild. (We used to duplicate the code because chrome-icu used to be very experimental so we do not want to greatly change the chromeos-chrome.ebuild for it. With chrome-icu method becoming stable, we can consider it now.)

Other questions

Emerging chrome-icu in cros chroot takes ages. What happened and how to resolve it?

This normally means that there is no prebuilt binary available for chrome-icu so it has to build chrome-icu from source and this needs the whole chrome repo. Because chrome-icu and chrome share a similar build mechanism, this usually implies that there is no prebuilt binary available for chrome too. So if you just did a repo sync and found it has to build chrome-icu from source in running build_packages, it means you will also need to build chrome from source too --- it is only because chrome depends on chrome-icu so the latter will be built first.

How to resolve it: There are a few methods that you could try,

  1. Run emerge-$BOARD -G chrome-icu and see if this succeeds and satisfies your needs. (This command enforce emerging chrome-icu from prebuilt binary.)
  2. If this is because the repo synced is very fresh, consider syncing to an older version of Chrome OS (e.g. sync to green).
  3. If this is caused by changing configurations (e.g. USE flag changes), you could let chrome-icu built from your local chrome checkout. First, you need to enter your chroot with the --chrome-root option pointing to your local chrome checkout. Then after entering the chroot, the chrome checkout is located at “~/chrome_root”. Second, now you can run CHROME_ORIGIN=LOCAL_SOURCE emerge-$BOARD chrome-icu to build it form local chrome checkout.

Why is chrome-icu a static library, not a shared library?

This is because: First, making it into a static library is easier and requires less modifications in chrome; Second, currently only two packages are using it, and total size increase of linking it statically is smaller than that of making it into a shared library.

After we make chrome-icu into a shared library, can chrome use it too to save more disk space?

The answer is no. This is because in chrome, icu is compiled with “control-flow integrity (CFI)” turned on. And CFI currently does not work well with shared libraries.

I want to use the chrome-icu mechanism to share other code in Chrome with Chrome OS. How should I do this?

Theoretically, the method used by chrome-icu should be able to share any code in chrome to Chrome OS. But considering that 1) the chrome-icu method is still very new and 2) it requires changes in both chrome and the infra configurations, we recommend you to first chat with the Chrome OS build team to discuss about your problem before moving forward. And there are other (e.g. more lightweight) sharing methods which may be more suitable.