Make Mixxx build with Qt6 #4621

Holzhaus · 2022-01-15T00:26:36Z

Makes it possible to build Mixxx with Qt6 without any compiler warnings or linker errors. Based on:

Next step is to fix the QML UI, because there are quite some incompatibilities apparently.

Be-ing · 2022-01-15T03:00:27Z

Interesting... how do you plan to remove no longer used code?

uklotzde · 2022-01-15T08:09:33Z

src/engine/enginebuffer.cpp

@@ -551,7 +553,9 @@ void EngineBuffer::slotTrackLoaded(TrackPointer pTrack,
    TrackPointer pOldTrack = m_pCurrentTrack;
    m_pause.lock();

+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)


Let's switch these code blocks, i.e. the Qt 6 variant should take precedence and should be placed before the legacy workaround. Consistency, makes it easier to throw away all legacy code later.

Holzhaus · 2022-01-15T15:24:35Z

Interesting... how do you plan to remove no longer used code?

I don't have a specific plan. The immediate goal was to make Mixxx build with Qt6 because that unblocks Qt6 QML development.

Removing everything from the old skin system at once is a huge task, and such tasks almost always lead to people giving up or being too intimidate by the size to even start working on it.

Instead, this just removes QGLWidget, the weird vsync hacks, etc. and leaves everything else intact, which keeps the PR small. Removing the legacy skin stuff from the Qt6 build can be done in smaller PRs, every at the source file level. In the worst case, we can remove it once we go Qt6-only.

Be-ing · 2022-01-15T15:37:54Z

I suppose procrastinating the linking problems is one way forward... I'm still puzzled how you expect to ever remove dead code without rewriting the entire library system from scratch.

Holzhaus · 2022-01-15T16:18:25Z

I suppose procrastinating the linking problems is one way forward... I'm still puzzled how you expect to ever remove dead code without rewriting the entire library system from scratch.

Well, the main goal of this PR is neither removing dead code nor rewriting the library system from scratch. The goal is making the Mixxx build with Qt6. I'm not saying the library system shouldn't be refactored or rewritten, or that we shouldn't remove the dead code at some point. But there is no need to connect these barely related topics and block progress on any of then unless the others are also solved. That kind of unnecessary scope creep is exactly what we previously identified as a problem with contributing to mixxx, and what wanted to avoid in the future. It scares people away from starting to work on it, leads to huge unreviewable PRs and generally makes stuff take way longer.

Now that Mixxx builds with Qt6, we don't have to fix all these issues sequentially anymore. We can work on stuff in parallel, for example:

@daschuer could investigate failing Qt6 tests,
@uklotzde could start replacing the library with aoide,
@Swiftb0y and @ronso0 could improve the QML skins and
I could remove the old legacy skins stuff.

And even if we don't remove the legacy skin code and don't replace the library yet, we already mostly solved the issue of Qt5 becoming deprecated. So in theory we could even publish a Qt6 Mixxx release where the dead code is still built (and hopefully removed by the linker).

Holzhaus · 2022-01-16T00:05:22Z

OK, build succeeds but some tests fail when built with Qt6. I'll check the clazy warning, but fixing the tests is out of scope for this PR. It's a separate branch anyway.

ywwg · 2022-01-16T00:08:41Z

Alternatively, you could disable the broken tests with a comment // Breaks under QT6. Unless you're worried people won't bother to fix the tests later :). But yes this sounds like a good plan.

Holzhaus · 2022-01-16T10:30:34Z

Alternatively, you could disable the broken tests with a comment // Breaks under QT6. Unless you're worried people won't bother to fix the tests later :). But yes this sounds like a good plan.

These tests fail:

	293 - EngineSyncTest.ZeroLatencyRateChangeQuant (Failed)
	294 - EngineSyncTest.ZeroLatencyRateDiffQuant (Failed)
	295 - EngineSyncTest.ActivatingSyncDoesNotCauseDrifting (Failed)
	302 - EngineSyncTest.SyncPhaseToPlayingNonSyncDeck (Failed)
	304 - EngineSyncTest.UserTweakPreservedInSeek (Failed)
	311 - EngineSyncTest.SeekStayInPhase (Failed)
	724 - WPushButtonTest.LongPressLatchTest (Failed)

The WPushButtonTest doesn't matter and can be disabled, but the other tests probably fail because of this commit: 18236e6

I have no idea how this complicated and weird visualplayposition/vsync code is supposed to work and how to remove it properly.
As a hack, I just replaced it with the playposition CO. I'd appreciate if someone who is more familiar with it could have a look.

From the Qt docs: > Note: This function is deprecated. For new code, use setSecsSinceEpoch(). > > Source: https://doc.qt.io/qt-5/qdatetime-obsolete.html#setTime_t

This is more efficient and also fixes a potential issue with Qt 6: ‘QSqlQuery::QSqlQuery(const QSqlQuery&)’ is deprecated: QSqlQuery is not meant to be copied. Use move construction instead. [-Werror=deprecated-declarations] 438 | parsePlaylistEntries(xml, current_path, | ~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~

…tures

In contrast to the `const char*` comparison, the comparison with QLatin1String is forward compatible with Qt 6.

These version checks actually result in compiler errors when trying to build this with Qt 6.

Qt6 replaces QStringRef with QStringView and updates the regular QString::left()/QString::mid() methods to return those.

…ng Qt6

That class is not available with Qt6.

This is not ideal, the whole VisualPlayPosition/VSyncThead stuff needs to be removed eventually.

This also fixes a test failure with Qt6. It's unknown why this happens, but the new code works with both Qt5 and Qt6 and is more readable and ideomatic anyway.

This makes is much easier to fix linker errors.

Holzhaus · 2022-01-21T22:54:02Z

All green. Now that the separate qt6 branch is obsolete, I'll close this and open a new PR against main.

Holzhaus added the code quality label Jan 15, 2022

github-actions bot added build library ui labels Jan 15, 2022

Holzhaus force-pushed the qt6-fixes branch 2 times, most recently from e28f9d0 to 95284da Compare January 15, 2022 01:19

Holzhaus changed the title ~~Qt6 fixes~~ Make Mixxx build with Qt6 Jan 15, 2022

Holzhaus force-pushed the qt6-fixes branch from 95284da to 21bca9b Compare January 15, 2022 01:31

uklotzde reviewed Jan 15, 2022

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Holzhaus force-pushed the qt6-fixes branch from 21bca9b to 472c11c Compare January 15, 2022 15:15

Holzhaus force-pushed the qt6-fixes branch from 472c11c to 4405177 Compare January 15, 2022 23:07

Holzhaus force-pushed the qt6-fixes branch from 4405177 to 18236e6 Compare January 16, 2022 00:13

Holzhaus added 10 commits January 17, 2022 22:21

BansheePlaylistModel: Use QDateTime::setSecsSinceEpoch instead setTime_t

a9bf0d8

From the Qt docs: > Note: This function is deprecated. For new code, use setSecsSinceEpoch(). > > Source: https://doc.qt.io/qt-5/qdatetime-obsolete.html#setTime_t

Library: Add Qt6 support for QtConcurrent::run() calls in library fea…

c7d9da0

…tures

Library: Compare QXMLStreamReader::name() with QLatin1String

0bc77e0

In contrast to the `const char*` comparison, the comparison with QLatin1String is forward compatible with Qt 6.

DlgPreferences: Do not add waveform preferences page with Qt 6

45448dc

ControlWidgetPropertyConnection: Add support for Qt6 QMetaType

64d99dd

widget: Remove some wrong Qt6 version checks

6ca14f9

These version checks actually result in compiler errors when trying to build this with Qt 6.

widget: Add some version checks for Qt6-style event position APIs

f60e3ee

WWidget: Add Qt6 version check for QTouchEvent APIs

a3b6225

WSliderComposed: Only use QStringRef with Qt < 6.0

936a789

Qt6 replaces QStringRef with QStringView and updates the regular QString::left()/QString::mid() methods to return those.

Holzhaus added 5 commits January 17, 2022 22:21

BaseTrackPlayer: Remove references to WaveformWidgetRenderer when usi…

cf9d0ae

…ng Qt6

LegacySkinParser: Return nullptr for widgets that use QGLWidget

7517d70

That class is not available with Qt6.

Remove VSyncThread from EngineBuffer/VisualPlayPosition with Qt6

7b9923f

This is not ideal, the whole VisualPlayPosition/VSyncThead stuff needs to be removed eventually.

WPushButton: Use more ideamatic QTestEventList::addDelay() method

5b0948e

This also fixes a test failure with Qt6. It's unknown why this happens, but the new code works with both Qt5 and Qt6 and is more readable and ideomatic anyway.

CMake: Re-enable large parts of the legacy UI with Qt6

a34c9c1

This makes is much easier to fix linker errors.

Holzhaus force-pushed the qt6-fixes branch from 18236e6 to a34c9c1 Compare January 20, 2022 23:26

WIP

73f23d6

Holzhaus force-pushed the qt6-fixes branch from ab8e897 to 73f23d6 Compare January 21, 2022 21:51

Holzhaus closed this Jan 21, 2022

Holzhaus mentioned this pull request Jan 21, 2022

Make Mixxx build with Qt6 #4640

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Make Mixxx build with Qt6 #4621

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Holzhaus commented Jan 15, 2022 •

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Make Mixxx build with Qt6 #4621

Make Mixxx build with Qt6 #4621

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