[Interest] Replacing icudtXX.dll without rebuilding Qt?

[John Layt]

On 17 January 2016 at 14:30, Elvis Stansvik <elvstone at gmail.com> wrote:

> 2016-01-17 14:48 GMT+01:00 Elvis Stansvik <elvstone at gmail.com>:
> > Hi all,
> >
> > In an effort to cut down on the size of the standalone ZIP
> > distribution of my small command line tool [1] which only uses QtCore,
> > and which to my knowledge does not depend on any localization
> > features, I'd like to try replacing the icudtXX.dll that I currently
> > take from the Qt bin directory with a custom one built using the ICU
> > Data Library Customizer [2].
>
> I've slightly misunderstood how the ICU Data Library Customizer works.
> I thought it would generate a icudtXX.dll, but it generates a .dat
> file to be used in the compilation of ICU.
>
> So now that I know that I have to re-build ICU with this .dat file, my
> question are:
>
> 1. Is it safe to replace the three icuXXXX.dll DLL files without also
> re-building Qt, provided that I use the exact same ICU version,
> compiled with the exact same compilation flags, but with a different
> .dat file?
>
> 2. If so, which parts of the .dat file can I safely exclude with the
> ICU Data Library Customizer? I don't think I need any of the features
> which Qt uses ICU for, but are there some parts that must be included
> for Qt to function at all?
>
> 3. Where can I find out how the ICU bundled with official Qt builds was
> built?
>

Advice for compiling ICU can be found at
https://wiki.qt.io/Compiling-ICU-with-MSVC, you don't need to worry about
compatibility so much as ICU offers no binary compatibility guarantees so
Qt only uses the C interface.

Frankly though, ICU is a pain to build and if you're rebuilding anything
I'd suggest you just rebuild Qt instead with the no ICU flag set. The only
thing you loose on Windows are proper collation support for Win XP, proper
toUpper/toLower support in tricky languages, and various Unicode look-up
tables. If you're not worried about those then this is a better path for
you.

John.
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