build: If both Qt4 and Qt5 are installed, use Qt5

[laanwj]

If both Qt4 and Qt5 development headers are installed, use Qt5. Building against Qt5 should be encouraged as that is where active development happens.

[maflcko]

Concept ACK

[paveljanik]

Please also remove --with-gui from ./configure --with-gui=qt5 in doc/build-osx.md.

[fanquake]

Concept ACK

On Wednesday, November 4, 2015, paveljanik notifications@github.com wrote:

Please also remove --with-gui from ./configure --with-gui=qt5 in doc/
build-osx.md.

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Reply to this email directly or view it on GitHub
#6938 (comment).

[laanwj]

Please also remove --with-gui from ./configure --with-gui=qt5 in doc/build-osx.md.

But that means you may end up without a GUI at all, if the proper dependencies cannot be found. Is that the intended behavior? If not, actively setting a GUI makes sense

[jonasschnelli]

utACK!

Please also remove --with-gui from ./configure --with-gui=qt5 in doc/build-osx.md.

We should definitively keep this.

[paveljanik]

@laanwj IMO configure without arguments should build whatever it can build (based on dependencies, and warn user that it can't build GUI because of missing deps) and you should be able to disable GUI with --disable-gui if you want to save compile time, do not care about GUI etc. Selecting which UI has sense only when you can and should select one of supported systems, but as we deprecate Qt4...

[jonasschnelli]

I think ./configure should only build the UI if the user did pass the --with-gui argument. In self build environment, i guess most users like to build bitcoin-core without the UI. But no strong opinion.

[paveljanik]

I'm happy with setting the --with-gui default to no, but when --with-gui is used, please do not require an argument and autoselect the highest qt available.

[jonasschnelli]

agree with @paveljanik

[laanwj]

I have no clue what happens if you do --with-gui without argument. Have you tested? You can do --without-gui if you want to build without GUI.

The default if you don't provide it is auto, which means that (with this pull), it will

• build with Qt5 if Qt5 is installed
• otherwise, build with Qt4 if Qt4 is installed
• otherwise, build without GUI

I have no intention of changing the semantics there. The only thing I'm changing is what Qt is selected by default, which IMO should be Qt5.

[jonasschnelli]

Agree. --with-gui already does auto-select. But right,.. as @laanwj mention, this PR would only change this auto-behavior to Qt5 instead of Qt4.

Do we need adaptation here:?
https://github.com/bitcoin/bitcoin/blob/master/build-aux/m4/bitcoin_qt.m4#L53

[laanwj]

@jonasschnelli good catch, updated

[paveljanik]

I just want to save the work again at qt6 bumb: just do not document the qt version in the doc/build-osx.md the Qt version at all.

[luke-jr]

Shouldn't the preferred Qt be based on what the OS default is configured for...?

[laanwj]

@luke-jr That may have been a better choice in the beginning, but right now, we're slowly moving away from Qt4. I expect to retain compatibility for the foreseeable future, but the GUI experience may be worse than Qt5, so we pick what is best for us.

[maflcko]

Note: I need to set --with-gui=qt4 or merge #6248, to get this working on fedora.

[maflcko]

Tested ACK. Nice, bitcoin-qt looks so much more clean when built with qt5! (No missing icons, styles, etc.)