material-components_material-components-android/lib/java/com/google/android/material/carousel/MaskableFrameLayout.java

/*
 * 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
 *
 *     https://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.google.android.material.carousel;

import android.annotation.SuppressLint;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.RectF;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.widget.FrameLayout;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.annotation.RestrictTo;
import androidx.annotation.RestrictTo.Scope;
import androidx.annotation.VisibleForTesting;
import androidx.core.math.MathUtils;
import com.google.android.material.animation.AnimationUtils;
import com.google.android.material.shape.AbsoluteCornerSize;
import com.google.android.material.shape.ClampedCornerSize;
import com.google.android.material.shape.ShapeAppearanceModel;
import com.google.android.material.shape.Shapeable;
import com.google.android.material.shape.ShapeableDelegate;

/** A {@link FrameLayout} than is able to mask itself and all children. */
public class MaskableFrameLayout extends FrameLayout implements Maskable, Shapeable {

  private float maskXPercentage = 0F;
  private final RectF maskRect = new RectF();
  @Nullable private OnMaskChangedListener onMaskChangedListener;
  @NonNull private ShapeAppearanceModel shapeAppearanceModel;
  private final ShapeableDelegate shapeableDelegate = ShapeableDelegate.create(this);
  @Nullable private Boolean savedForceCompatClippingEnabled = null;

  public MaskableFrameLayout(@NonNull Context context) {
    this(context, null);
  }

  public MaskableFrameLayout(@NonNull Context context, @Nullable AttributeSet attrs) {
    this(context, attrs, 0);
  }

  public MaskableFrameLayout(
      @NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    setShapeAppearanceModel(
        ShapeAppearanceModel.builder(context, attrs, defStyleAttr, 0, 0).build());
  }

  @Override
  protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    super.onSizeChanged(w, h, oldw, oldh);
    onMaskChanged();
  }

  @Override
  protected void onAttachedToWindow() {
    super.onAttachedToWindow();
    // Restore any saved force compat clipping setting.
    if (savedForceCompatClippingEnabled != null) {
      shapeableDelegate.setForceCompatClippingEnabled(this, savedForceCompatClippingEnabled);
    }
  }

  @Override
  protected void onDetachedFromWindow() {
    // When detaching from the window, force canvas clipping to avoid any transitions from releasing
    // the mask outline set by the MaskableDelegate's ViewOutlineProvider, if any.
    savedForceCompatClippingEnabled = shapeableDelegate.isForceCompatClippingEnabled();
    shapeableDelegate.setForceCompatClippingEnabled(this, true);
    super.onDetachedFromWindow();
  }

  @Override
  public void setShapeAppearanceModel(@NonNull ShapeAppearanceModel shapeAppearanceModel) {
    this.shapeAppearanceModel =
        shapeAppearanceModel.withTransformedCornerSizes(
            cornerSize -> {
              if (cornerSize instanceof AbsoluteCornerSize) {
                // Enforce that the corners of the shape appearance are never larger than half the
                // width of the shortest edge. As the size of the mask changes, we never want the
                // corners to be larger than half the width or height of this view.
                return ClampedCornerSize.createFromCornerSize((AbsoluteCornerSize) cornerSize);
              } else {
                // Relative corner size already enforces a max size based on shortest edge.
                return cornerSize;
              }
            });
    shapeableDelegate.onShapeAppearanceChanged(this, this.shapeAppearanceModel);
  }

  @NonNull
  @Override
  public ShapeAppearanceModel getShapeAppearanceModel() {
    return shapeAppearanceModel;
  }

  /**
   * Sets the percentage by which this {@link View} masks by along the x axis.
   *
   * @param percentage 0 when this view is fully unmasked. 1 when this view is fully masked.
   */
  @Override
  public void setMaskXPercentage(float percentage) {
    percentage = MathUtils.clamp(percentage, 0F, 1F);
    if (maskXPercentage != percentage) {
      this.maskXPercentage = percentage;
      onMaskChanged();
    }
  }

  /**
   * Gets the percentage by which this {@link View} is masked by along the x axis.
   *
   * @return a float between 0 and 1 where 0 is fully unmasked and 1 is fully masked.
   */
  @Override
  public float getMaskXPercentage() {
    return maskXPercentage;
  }

  /** Gets a {@link RectF} that this {@link View} is masked itself by. */
  @NonNull
  @Override
  public RectF getMaskRectF() {
    return maskRect;
  }

  @Override
  public void setOnMaskChangedListener(@Nullable OnMaskChangedListener onMaskChangedListener) {
    this.onMaskChangedListener = onMaskChangedListener;
  }

  private void onMaskChanged() {
    if (getWidth() == 0) {
      return;
    }
    // Translate the percentage into an actual pixel value of how much of this view should be
    // masked away.
    float maskWidth = AnimationUtils.lerp(0f, getWidth() / 2F, 0f, 1f, maskXPercentage);
    maskRect.set(maskWidth, 0F, (getWidth() - maskWidth), getHeight());
    shapeableDelegate.onMaskChanged(this, maskRect);
    if (onMaskChangedListener != null) {
      onMaskChangedListener.onMaskChanged(maskRect);
    }
  }

  /**
   * Set whether this view should always use canvas clipping to clip to its masked shape.
   *
   * @hide
   */
  @VisibleForTesting
  @RestrictTo(Scope.LIBRARY_GROUP)
  public void setForceCompatClipping(boolean forceCompatClipping) {
    shapeableDelegate.setForceCompatClippingEnabled(this, forceCompatClipping);
  }

  @SuppressLint("ClickableViewAccessibility")
  @Override
  public boolean onTouchEvent(MotionEvent event) {
    // Only handle touch events that are within the masked bounds of this view.
    if (!maskRect.isEmpty() && event.getAction() == MotionEvent.ACTION_DOWN) {
      float x = event.getX();
      float y = event.getY();
      if (!maskRect.contains(x, y)) {
        return false;
      }
    }
    return super.onTouchEvent(event);
  }

  @Override
  protected void dispatchDraw(Canvas canvas) {
    shapeableDelegate.maybeClip(canvas, super::dispatchDraw);
  }
}