I also like this idea very much. Still needs a reflective scanner, but it's far more easier to understand and use.
A couple of comments/questions: - I would recommend against the scanner figuring out the property name: the property names are codified by the CSS reference which serves as a normative document in this case - isSettable() logic might be more complex than (prop == null && !(prop.isBound)), see Node.translateXProperty. How would that work with annotations? What do you think? -andy From: Nir Lisker <nlis...@gmail.com> Date: Wednesday, December 6, 2023 at 02:37 To: Andy Goryachev <andy.goryac...@oracle.com> Cc: Michael Strauß <michaelstr...@gmail.com>, openjfx-dev <openjfx-dev@openjdk.org> Subject: [External] : Re: Reflective discovery of styleable properties I thought about the option of reflection, but I opted to propose annotations instead. The following is my reasoning. Firstly, reflection is very magic-y. The author of the class has no indication of what side effects happen due to the code they write, the output (css handling in this case) comes out of nowhere from their perspective. As with other reflection cases, it is a "pull" rather than "push" approach - you don't write what should happen, you let someone else decide that. For writers of skin/control classes, this means that they need to know exactly what constitutes a hook for the reflection mechanism, or face surprises. There is no compile time check that tells you whether you have declared your styleable property properly or not (without an external ad-hoc checker). We do this somewhat with properties - any method of the form "...property()" gets special treatment, but this is for the docs. I don't think we have code that depends on this other than in tests. Secondly, the proposed mechanism depends on the runtime type, not the declared type. As a user, I see no indication in the API whether a property is styleable or not. This is also (what I would consider) a problem with the current state. When I thought about using reflection to solve this, I at least thought to specify the declared type of the property as styleable, like StyleableBooleanProperty instead of BooleanProperty (restricting the returned type is backwards compatible). A downside of this is that it gives access to the methods of StyleableProperty, which are not useful for the user, I think, but maybe someone has a use for them. Thirdly, maybe I want to declare a styleable property not to be used automatically. I can't think off the top of my head when I would want to do that, but I'm also not a heavy css user. Are we sure that just initializing a property with a styleable runtime type should *always* be caught by this process? To compare, annotations have the following benefits: Firstly, they are declarative, which means no surprises for the class author (WYSIWYG). This also allows more flexibility/control over which properties get special treatment via an opt-in mechanism. Secondly, They can also be displayed in the JavaDocs (via @Documented) with their assigned values. For example, the padding property of Region can be annotated with @Styleable(property="-fx-padding"), informing the user both that this value can be set by css, and how to do it. Interestingly, the annotation doesn't need to be public API to be displayed, so we are not bound by contracts. In terms of similarities: In both the reflection and the annotation proposals, the steps are: 1. Create styleable properties. 2. That's it. It's just that step 1 also adds an annotation to the creation of the property (which was/is a 2-step process anyway, declaring the property and its css metadata). Annotations also require a processor to read the data from their values and target (the field/method). This is a bit of work, but Michael's CssMetaDataCache class is basically that - read the data from the class (via reflection or annotations) and store it in a map. The logic should be the same, just the method to obtain the data is different. Both, as a result, have the benefits of handling control/skin combinations (what I mentioned in the point "Usable both in controls and in skins (or other classes)"). The benefit of co-locating the property and its css metadata in the class itself also remains. To summarize, both approaches eliminate all the clutter of writing styleable properties (John, will you like to create styleable properties now? [1] :) ), both apply the flexibility of caching per class, both allow better structuring of the class, but they read the properties differently and have a different level of declarativness. [1] https://mail.openjdk.org/pipermail/openjfx-dev/2023-December/044010.html On Tue, Dec 5, 2023 at 11:21 PM Andy Goryachev <andy.goryac...@oracle.com<mailto:andy.goryac...@oracle.com>> wrote: I like the idea. I wonder if it is possible to reduce the amount of boilerplate code? For example, a CssMetaData can have a setGetter(Function<S, StyleableProperty<V>> getter) method which supplies the property reference? This way CssMetaData.isSettable(Node) and CssMetaData.getStyleableProperty(Node) can be implemented in the base class (there are more complicated cases, so perhaps setIsSettable(Predicate<Node>) would also be required). Example: CssMetaData.<ControlExample,Font>of("-fx-font", Font.getDefault(), (n) -> n.font) Just a thought. What do you think? -andy From: openjfx-dev <openjfx-dev-r...@openjdk.org<mailto:openjfx-dev-r...@openjdk.org>> on behalf of Michael Strauß <michaelstr...@gmail.com<mailto:michaelstr...@gmail.com>> Date: Sunday, December 3, 2023 at 22:02 To: openjfx-dev <openjfx-dev@openjdk.org<mailto:openjfx-dev@openjdk.org>> Subject: Reflective discovery of styleable properties Following up the discussion around the CssMetaData API, I'd like to chime in with yet another idea. To recap, here's Nir's summary of the current API [0]: "Let's look at what implementation is required from a user who wants to write their own styleable control: 1. Create styleable properties. 2. Create a list of these properties to be passed on. 3. Create a public static method that returns the concatenation of this list with the one of its parent. (This method happens to be poorly documented, as mstr said.) 4. Create a public non-static method that calls the static method in a forced-override pattern because otherwise you will be calling the wrong static method. (This method's docs seem to be just wrong because you don't always want to delegate to Node's list.)" I think this could reasonably be replaced with the following implementation requirements: 1. Create styleable properties. 2. That's it. Let's look at what we're actually trying to do: create a list of CSS-styleable property metadata of a class. But we can easily do that without all of the boilerplate code. When ´Node.getCssMetaData()` is invoked, all public methods of the class are reflectively enumerated, and metadata is retrieved from `Property` and `StyleableProperty` getters. This is a price that's only paid once for any particular class (i.e. not for every instance). The resulting metadata list is cached and reused for all instances of that particular class. As a further optimization, metadata lists are also cached and deduplicated for Control/Skin combinations (currently every Control instance has its own copy of the metadata list). Another benefit of this approach is that the CssMetaData can now be co-located with the property implementation, and not be kept around in other parts of the source code file. Here's how that looks like when a new "myValue" property is added to MyClass: StyleableDoubleProperty myValue = new SimpleStyleableDoubleProperty(this, "myValue") { static final CssMetaData<MyClass, Number> METADATA = new CssMetaData<MyClass, Number>( "-fx-my-value", SizeConverter.getInstance(), USE_COMPUTED_SIZE) { @Override public boolean isSettable(MyClass node) { return !node.myValue.isBound(); } @Override public StyleableProperty getStyleableProperty( MyClass node) { return node.myValue; } }; @Override public CssMetaData getCssMetaData() { return METADATA; } }; public final DoubleProperty myValueProperty() { return myValue; } It is not required to override the `getCssMetaData()` method, nor is it required to redeclare a new static `getClassCssMetaData()` method. It is also not required to manually keep the list of styleable properties in sync with the list of CSS metadata. I've prototyped this concept for the `Node`, `Region` and `Control` classes [1]. [0] https://mail.openjdk.org/pipermail/openjfx-dev/2023-December/044046.html [1] https://github.com/openjdk/jfx/pull/1299<https://urldefense.com/v3/__https:/github.com/openjdk/jfx/pull/1299__;!!ACWV5N9M2RV99hQ!K7nDyvMP0PzEOLu-h9yGCoHIoSnny6LJ5acSISP81wBjJjP2z4VcDA6CIMU_Wvzxv2QJgPTsB6F9wtnzMK97$>
