commonMain.androidx.compose.ui.graphics.drawscope.DrawContext.kt Maven / Gradle / Ivy
/*
* Copyright 2020 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.ui.graphics.drawscope
import androidx.compose.ui.geometry.Size
import androidx.compose.ui.graphics.Canvas
import androidx.compose.ui.graphics.layer.GraphicsLayer
import androidx.compose.ui.unit.Density
import androidx.compose.ui.unit.LayoutDirection
/**
* Default density value that is used as a stub to provide a non-null
* density parameter within CanvasDrawScope.
* Density is provided as a parameter as part of the draw call to
* issue drawing commands into a target canvas so this Density value is never consumed
*/
internal val DefaultDensity = Density(1.0f, 1.0f)
/**
* Object that provides the dependencies to support a [DrawScope] drawing environment.
* Namely this provides the drawing bounds represented as a size as well as the target
* [Canvas] to issue drawing commands into. Additionally the [DrawContext] handles
* updating [Canvas] state during transformations and updating the size of the drawing
* bounds that may occur during these transformations.
*
* This exposes necessary internal state to the implementation of the [DrawScope] in order
* to support inline scoped transformation calls without allowing consumers of [DrawScope]
* to modify state directly thus maintaining the stateless API surface
*/
interface DrawContext {
/**
* The current size of the drawing environment
*/
var size: Size
/**
* The target canvas to issue drawing commands
*/
var canvas: Canvas
get() = EmptyCanvas()
set(_) {}
/**
* The controller for issuing transformations to the drawing environment
*/
val transform: DrawTransform
/**
* [LayoutDirection] of the layout being drawn in.
*/
var layoutDirection: LayoutDirection
get() = LayoutDirection.Ltr
set(_) {}
/**
* [Density] used to assist in conversions of density independent pixels to raw pixels to draw
*/
var density: Density
get() = DefaultDensity
set(_) {}
/**
* Current [GraphicsLayer] we are drawing into. Might be null if the [canvas] is not provided
* by a [GraphicsLayer], for example in the case of a software-accelerated drawing.
*/
var graphicsLayer: GraphicsLayer?
get() = null
set(_) {}
}