| /* |
| * Copyright 2019 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package androidx.compose |
| |
| /** |
| * [Composable] functions are the fundamental building blocks of an application built with Compose. |
| * |
| * [Composable] can be applied to a function or lambda to indicate that the function/lambda can be |
| * used as part of a composition to describe a transformation from application data into a |
| * tree or hierarchy. |
| * |
| * Annotating a function or expression with [Composable] changes the type of that function or |
| * expression. For example, [Composable] functions can only ever be called from within another |
| * [Composable] function. A useful mental model for [Composable] functions is that an implicit |
| * "composable context" is passed into a [Composable] function, and is done so implicitly when it |
| * is called from within another [Composable] function. This "context" can be used to store |
| * information from previous executions of the function that happened at the same logical point of |
| * the tree. |
| */ |
| @MustBeDocumented |
| @Retention(AnnotationRetention.BINARY) |
| @Target( |
| // function declarations |
| // @Composable fun Foo() { ... } |
| // lambda expressions |
| // val foo = @Composable { ... } |
| AnnotationTarget.FUNCTION, |
| |
| // type declarations |
| // var foo: @Composable () -> Unit = { ... } |
| // parameter types |
| // foo: @Composable () -> Unit |
| AnnotationTarget.TYPE, |
| |
| // composable types inside of type signatures |
| // foo: (@Composable () -> Unit) -> Unit |
| AnnotationTarget.TYPE_PARAMETER, |
| |
| // composable property declarations |
| // @Composable val foo: Int get() { ... } |
| AnnotationTarget.PROPERTY |
| ) |
| annotation class Composable |