[Development] Qt Examples need to be self-contained

[Fabian Kosmale]

Hi,

just for clarification: If we factor out shared resources into a library, then that wouldn't be one big QtExamplesShared module,
but rather one library per module (unless something actually needs to be shared across multiple modules, e.g. icons).
Anything else would require moving examples to a leaf module like qtdoc to handle the dependencies in the CI, which isn't
something we want here.

I would argue that putting actually shared resources into such libraries is a good idea, regardless of whether we need it for
junctions or not – after all, it promotes a sane way of sharing resources in our examples. Whereas I doubt that we want to
promote the relative path inclusion for the projects our users start.

Regards,
Fabian

________________________________________
Von: Development <development-bounces at qt-project.org> im Auftrag von Kai Köhne via Development <development at qt-project.org>
Gesendet: Donnerstag, 7. März 2024 13:02
An: qt-development
Betreff: [Development] Qt Examples need to be self-contained

Hi,

We have quite a few Qt examples and tutorials that share assets  (images, sources, ...) via relative paths in the file system. That is, there's often a 'shared' directory that multiple examples use by relative paths (see e.g. https://code.qt.io/cgit/qt/qtdeclarative.git/tree/examples/quick/shared). My suggestion is to officially ban this, and

  *
either duplicate the relevant sources and assets in the respective example directories, or
  *
create a static 'QtModuleExamplesPrivate' library that is built as part of Qt, and can be referenced by these examples - something we already discussed & implemented before e.g. for sharing icons.

Proposed change in QUIP-13  is at https://codereview.qt-project.org/c/meta/quips/+/546086

Why this change? Qt Creator 13 will get a feature to shorten build paths by creating Junction Points (basically symbolic links) on Windows. This is to prevent file paths and build command lines from becoming too long, an issue that has been a never-ending source of frustration especially for new users on Windows

The issue of long file paths breaking builds is something that has been impeding users since forever. It became even more urgent though in the last years due to the deep nested structures that Qt Quick and the relevant tooling endorses (see e.g. https://bugreports.qt.io/browse/QTBUG-117413). Its root cause can arguably only be fixed on Microsoft's side - but chances for this are IMO slim ... So, shortening build paths as part of Qt Creator seems our best 'general' cure for now. As the build path will however not be the source path, navigating across the file system with things like

  #include "../../../../shared/shared.h"

will break.

If we agree on this, we would prepare matching bug reports for affected examples.

Regards

Kai

PS: To be clear, this is not something we still have to fix for Qt 6.7.0.  For now, the use of Junction points in Qt Creator is still opt-in. When we fix examples, we should still backport them to older Qt versions though.


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