[Interest] Replacing icudtXX.dll without rebuilding Qt?

[Koehne Kai]

> -----Original Message-----
> From: Interest [mailto:interest-bounces at qt-project.org] On Behalf Of Elvis
> Stansvik
> Sent: Tuesday, January 19, 2016 8:38 PM
> To: John Layt <jlayt at kde.org>
> Cc: interest at qt-project.org Interest <interest at qt-project.org>
> Subject: Re: [Interest] Replacing icudtXX.dll without rebuilding Qt?
> 
> 2016-01-17 15:46 GMT+01:00 John Layt <jlayt at kde.org>:
> >
> >
> > 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.
> 
> Hi again John,
> 
> I'm now in the process of setting up a separate Git repo with an
> appveyor.yml file such that it'll build minimal ICU DLLs for me.
> Mostly because I wanted to see how easy/hard it'd be. It seems to work out
> well so far, just a few kinks to work out.
> 
> However, I'm still wondering if there's some definitive place where I can see
> which exact version of ICU was used for the official builds.
> Perhaps you know where this would be?

The used ICU libs are hosted under

http://download.qt.io/development_releases/prebuilt/icu/

Anyhow, as John already said: Since we're using just the stable C API I wouldn't expect
any problems, even if you use another compiler / another patch level version of ICU.

> I know I can look at the file names of installed DLLs (e.g.
> icudt54.dll would indicate ICU 54.x was used), but I'd rather be double sure
> and see the scripts used to build the ICU that official Qt uses.

The script should be at http://code.qt.io/cgit/qtsdk/qtsdk.git/tree/packaging-tools/bld_icu_tools.py.

Regards

Kai