AndroidMultiParagraphDraw.kt

/*
 * Copyright 2022 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.text.platform

import android.graphics.Matrix
import androidx.compose.ui.geometry.Size
import androidx.compose.ui.graphics.BlendMode
import androidx.compose.ui.graphics.Brush
import androidx.compose.ui.graphics.Canvas
import androidx.compose.ui.graphics.ShaderBrush
import androidx.compose.ui.graphics.Shadow
import androidx.compose.ui.graphics.SolidColor
import androidx.compose.ui.graphics.drawscope.DrawStyle
import androidx.compose.ui.text.ExperimentalTextApi
import androidx.compose.ui.text.MultiParagraph
import androidx.compose.ui.text.style.TextDecoration
import androidx.compose.ui.util.fastForEach

@OptIn(ExperimentalTextApi::class)
internal actual fun MultiParagraph.drawMultiParagraph(
    canvas: Canvas,
    brush: Brush,
    alpha: Float,
    shadow: Shadow?,
    decoration: TextDecoration?,
    drawStyle: DrawStyle?,
    blendMode: BlendMode
) {
    canvas.save()

    if (paragraphInfoList.size <= 1) {
        drawParagraphs(canvas, brush, alpha, shadow, decoration, drawStyle, blendMode)
    } else {
        when (brush) {
            is SolidColor -> {
                drawParagraphs(canvas, brush, alpha, shadow, decoration, drawStyle, blendMode)
            }
            is ShaderBrush -> {
                var height = 0f
                var width = 0f
                paragraphInfoList.fastForEach {
                    height += it.paragraph.height
                    width = maxOf(width, it.paragraph.width)
                }
                val shader = brush.createShader(Size(width, height))
                val matrix = Matrix()
                shader.getLocalMatrix(matrix)
                paragraphInfoList.fastForEach {
                    it.paragraph.paint(
                        canvas = canvas,
                        brush = ShaderBrush(shader),
                        alpha = alpha,
                        shadow = shadow,
                        textDecoration = decoration,
                        drawStyle = drawStyle,
                        blendMode = blendMode
                    )
                    canvas.translate(0f, it.paragraph.height)
                    matrix.setTranslate(0f, -it.paragraph.height)
                    shader.setLocalMatrix(matrix)
                }
            }
        }
    }

    canvas.restore()
}

@OptIn(ExperimentalTextApi::class)
private fun MultiParagraph.drawParagraphs(
    canvas: Canvas,
    brush: Brush,
    alpha: Float,
    shadow: Shadow?,
    decoration: TextDecoration?,
    drawStyle: DrawStyle?,
    blendMode: BlendMode
) {
    paragraphInfoList.fastForEach {
        it.paragraph.paint(canvas, brush, alpha, shadow, decoration, drawStyle, blendMode)
        canvas.translate(0f, it.paragraph.height)
    }
}