This patch completes the cumulative work done in previous patches.
- Uses qmlRegisterModuleImport() to register styles. This has some
added requirements:
- Each style must now be a QML module -- that is, it must have a
qmldir file.
- As a result of the above, the module must be available within the
QML import path in order to be found.
- The various forms of accepted style names have been reduced down to
one ("Material", "MyStyle", etc). See below for an explanation of
why.
- The following API in QQuickStyle is removed:
addStylePath(), availableStyles(), path(), stylePathList(). These
no longer make sense now that we reuse the existing QML import
system.
- Adds the tst_qquickstyleselector auto test back as "styleimports".
qmlRegisterModuleImport() vs resolvedUrl()
Previously we would use QQuickStyleSelector to select individual
QML files based on which style was set. We'd do this once when
QtQuick.Controls was first imported.
With Qt 6, and the requirement that each style be a proper QML
module, qmlRegisterModuleImport() was introduced. This allows us
to "link" one import with another. For an example of what this
looks like in practice, suppose the style was set to "MyStyle",
and the fallback to "Material". The "QtQuick.Controls" import
will be linked to "MyStyle", "MyStyle" to
"QtQuick.Controls.Material", and as a final fallback (for controls
like Action which only the Default style implements),
"QtQuick.Controls.Material" to "QtQuick.Controls.Default".
This is the same behavior as in Qt 5 (see qquickstyleselector.cpp):
// 1) requested style (e.g. "MyStyle", included in d->selectors)
// 2) fallback style (e.g. "Material", included in d->selectors)
// 3) default style (empty selector, not in d->selectors)
This is a necessary step to enable compilation of QML to C++.
Reducing the set of accepted style names
The problem
In QtQuickControls2Plugin() we need to call
QQuickStylePrivate::init(baseUrl()) in order to detect if the style
is a custom style in QQuickStyleSpec::resolve() (by checking if the
style path starts with the base URL). In Qt 5, init() is called in
QtQuickControls2Plugin::registerTypes(), but in Qt 6 that's too
late, because we need to call qmlRegisterModuleImport() in the
constructor. qmlRegisterModuleImport() itself requires the style to
have already been set in order to create the correct import URI
("QtQuick.Controls.X" for built-in styles, "MyCustomStyle" for
custom styles).
The solution
By reducing the valid forms for style names down to one:
./myapp -style MyStyle
we solve the problem of needing baseUrl() to determine if the
style is a custom style or not, but needing to call it too early
(since we now call qmlRegisterModuleImport() in
QtQuickControls2Plugin(), which itself requires the style to have
already been set). baseUrl() can't have been set before the
constructor is finished.
All of the various forms for _setting_ a style are still valid;
environment variables, qtquickcontrols2.conf, etc.
[ChangeLog][Important Behavior Changes] Custom styles must now have
a qmldir that lists the files that the style implements. For example,
for a style that only implements Button:
---
module MyStyle
Button 1.0 Button.qml
---
In addition, there is now only one valid, case-sensitive form for style
names: "Material", "MyStyle", etc.
These changes are done to help enable the compilation of QML code to
C++, as well as improve tooling capabilities.
[ChangeLog][Important Behavior Changes] The following API was removed:
- QQuickStyle::addStylePath()
- QQuickStyle::availableStyles()
- QQuickStyle::path()
- QQuickStyle::stylePathList()
- QT_QUICK_CONTROLS_STYLE_PATH
This API is no longer necessary and/or able to be provided now that
styles are treated as regular QML modules.
Task-number: QTBUG-82922
Change-Id: I3b281131903c7c3c1cf0616eb7486a872dccd730
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
501bc44bb0