commonMain.com.skydoves.landscapist.placeholder.shimmer.FlashShimmer.kt Maven / Gradle / Ivy

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A pluggable, highly optimized Jetpack Compose image loading library that fetches and displays network images with Glide, Coil, and Fresco.
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/*
 * Designed and developed by 2020-2023 skydoves (Jaewoong Eum)
 *
 * 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 com.skydoves.landscapist.placeholder.shimmer

import androidx.compose.animation.core.Animatable
import androidx.compose.animation.core.LinearEasing
import androidx.compose.animation.core.infiniteRepeatable
import androidx.compose.animation.core.tween
import androidx.compose.foundation.Canvas
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.runtime.Composable
import androidx.compose.runtime.LaunchedEffect
import androidx.compose.runtime.remember
import androidx.compose.ui.Modifier
import androidx.compose.ui.geometry.Offset
import androidx.compose.ui.geometry.Rect
import androidx.compose.ui.graphics.BlendMode
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.graphics.LinearGradientShader
import androidx.compose.ui.graphics.Matrix
import androidx.compose.ui.graphics.Paint
import androidx.compose.ui.graphics.PaintingStyle
import androidx.compose.ui.graphics.drawscope.drawIntoCanvas
import androidx.compose.ui.graphics.withSaveLayer
import androidx.compose.ui.platform.LocalDensity
import androidx.compose.ui.unit.Dp
import kotlin.math.max
import kotlin.math.min
import kotlin.math.tan

/**
 * Create a shimmering effect composable with base and highlighting colors.
 *
 * @param modifier basic modifier, must be applied fillMaxSize().
 * @param baseColor base background color of this composable.
 * @param highlightColor highlight shimmering effect color of this composable.
 * @param intensity controls the brightness of the highlight at the center.
 * @param dropOff controls the size of the fading edge of the highlight.
 * @param tilt angle at which the highlight is tilted, measured in degrees.
 * @param durationMillis animation duration of the shimmering start to end.
 */
@Composable
public fun Shimmer(
  modifier: Modifier = Modifier,
  baseColor: Color,
  highlightColor: Color,
  shimmerWidth: Dp? = null,
  intensity: Float = DefaultShimmerIntensity,
  dropOff: Float = DefaultShimmerDropOff,
  tilt: Float = DefaultShimmerTilt,
  durationMillis: Int = DefaultDurationMillis,
) {
  val shimmerWidthPx = with(LocalDensity.current) { shimmerWidth?.toPx() }
  val animatedProgress = remember { Animatable(0f) }
  LaunchedEffect(key1 = baseColor) {
    animatedProgress.animateTo(
      targetValue = 1f,
      animationSpec = infiniteRepeatable(
        animation = tween(durationMillis = durationMillis, easing = LinearEasing),
      ),
    )
  }

  val emptyPaint = Paint()
  val paint = Paint().apply {
    isAntiAlias = true
    style = PaintingStyle.Fill
    blendMode = BlendMode.SrcIn
  }

  val shaderColors = listOf(
    baseColor,
    highlightColor,
    highlightColor,
    baseColor,
  )
  val shaderColorStops = listOf(
    max((1f - intensity - dropOff) / 2f, 0f),
    max((1f - intensity - 0.001f) / 2f, 0f),
    min((1f + intensity + 0.001f) / 2f, 1f),
    min((1f + intensity + dropOff) / 2f, 1f),
  )

  Box(modifier = modifier) {
    Canvas(modifier = Modifier.fillMaxSize()) {
      val gradientFrom = Offset(-size.width / 2, 0f)
      val gradientTo = -gradientFrom
      val tiltTan = tan(tilt.toDouble() * DEGREES_TO_RADIANS)
      val width = shimmerWidthPx ?: (size.width + tiltTan * size.height).toFloat()

      val dx = offset(-width, width * 1.5f, animatedProgress.value)
      val shaderMatrix = Matrix().apply {
        reset()
        rotateX(size.width / 2f)
        rotateY(size.height / 2f)
        rotateZ(-tilt)
        translate(dx, 0f)
      }

      paint.shader = LinearGradientShader(
        from = shaderMatrix.map(gradientFrom),
        to = shaderMatrix.map(gradientTo),
        colors = shaderColors,
        colorStops = shaderColorStops,
      )

      val drawArea = Rect(Offset(0f, 0f), size)
      drawIntoCanvas { canvas ->
        canvas.withSaveLayer(
          bounds = drawArea,
          paint = emptyPaint,
        ) {
          canvas.drawRect(drawArea, paint)
        }
      }
    }
  }
}

/** returns a shimmer matrix offset. */
private fun offset(start: Float, end: Float, percent: Float): Float {
  return start + (end - start) * percent
}

/** A definition of the default intensity. */
internal const val DefaultShimmerIntensity = 0f

/** A definition of the default dropOff. */
internal const val DefaultShimmerDropOff = 0.5f

/** A definition of the default tilt. */
internal const val DefaultShimmerTilt = 20f

/** A definition of the default duration. */
internal const val DefaultDurationMillis = 650

private const val DEGREES_TO_RADIANS = 0.017453292519943295