BugFix: Compilation Failure for Qt6 Due to Deprecated Members

[ShaopengLin]

Fixes #1102

Tested on Qt 6.2.4.

src/contentmanagermodel.cpp:40:16: error: ‘class QVariant’ has no member named ‘type’; did you mean ‘typeId’?
   39 |         if ( r.type() == QVariant::ByteArray )
      |                ^~~~
      |                typeId
src/contentmanagermodel.cpp:40:36: error: ‘ByteArray’ is not a member of ‘QVariant’
   39 |         if ( r.type() == QVariant::ByteArray )
      |

QVariant.type() and QVariant::ByteArray has been deprecated. We will use the new function QVariant.typeId() and QMetaType::QByteArray from Qt6.

I recommend we have compilation pipelines to check both Qt versions.

Fix:

• Added macro to make the application still compatible with Qt 5
• Used equivalent new features from Qt 6 to replace the lines.

[kelson42]

I recommend we have compilation pipelines to check both Qt versions.

Yes, see #1103

[veloman-yunkan]

Maybe your change is the best way to fix the current problem. However I suspect that you don't know about src/portutils.h. See if you can come up with a convenient and future-proof utility that can be used for portably checking the type of a QVariant. If not, we will merge the PR as is.

[veloman-yunkan]

On a second thought, in case there is no good way to move the conditional compilation into portutils.h, I would like to restrict the conditional compilation to the least amount of code as follows:

        const bool gotThumbnailData =
#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
            r.type() == QVariant::ByteArray;
#else
            r.typeId() == QMetaType::QByteArray;
#endif

        if ( gotThumbnailData )
            return r;

Above can be turned into a more readable form if we introduce a special macro that will select during compile time the right expression depending on the version of Qt used:

        const bool gotThumbnailData = QT5VS6(r.type() == QVariant::ByteArray,
                                             r.typeId() == QMetaType::QByteArray);

        if ( gotThumbnailData )
            return r;

[veloman-yunkan]

Same here.

In case you wonder what the proposed change improves, it minimizes the amount of code duplication between the conditionally compiled pieces and hence the risk that, for whatever reasons, one of the branches is updated and the other is not.

[ShaopengLin]

@veloman-yunkan I found two ways for type checking for both Qt5 and 6:

• r.typeName() == QMetaType(QMetaType::QByteArray).name()
• r.userType() == QMetaType::QByteArray

❌ The typeName approach isn't something we want as string comparison is unnecessary overhead when we have ints.

✅ The userType approach works well as it is:

• Same as type() for non-user defined type in Qt5
• Exact same behavior as typeId() in Qt6
• The change commit also recommends using userType instead, which I will use in this commit.

I imagine in the future, they might decide to remove either typeId() or userType(). Since its 50/50 we can just use userType.

[veloman-yunkan]

Perfect!