src/android/src/com/google/android/inputmethod/japanese/view/PopUpFrameWindowDrawable.java

// Copyright 2010-2014, Google Inc.
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package org.mozc.android.inputmethod.japanese.view;

import com.google.common.base.Optional;

import android.graphics.BlurMaskFilter;
import android.graphics.BlurMaskFilter.Blur;
import android.graphics.Canvas;
import android.graphics.LinearGradient;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.graphics.Rect;
import android.graphics.Shader;
import android.graphics.Shader.TileMode;

/**
 * Drawable to render a popup window with a frame.
 *
 */
public class PopUpFrameWindowDrawable extends BaseBackgroundDrawable {

  private final int frameWidth;

  private final int topColor;
  private final int bottomColor;
  private final int borderColor;
  private final int innerPaneColor;
  private final float shadowSize;

  private final Rect outerFrameRect = new Rect();
  private final Rect innerFrameRect = new Rect();
  private final Paint paint = new Paint();
  private final BlurMaskFilter blurMaskFilter;
  private Optional<Shader> shader = Optional.absent();

  public PopUpFrameWindowDrawable(
      int leftPadding, int topPadding, int rightPadding, int bottomPadding,
      int frameWidth, float shadowSize,
      int topColor, int bottomColor, int borderColor, int innerPaneColor) {
    super(leftPadding, topPadding, rightPadding, bottomPadding);

    this.frameWidth = frameWidth;
    this.topColor = topColor;
    this.bottomColor = bottomColor;
    this.borderColor = borderColor;
    this.innerPaneColor = innerPaneColor;
    this.shadowSize = shadowSize;
    this.blurMaskFilter = new BlurMaskFilter(shadowSize, Blur.INNER);
  }

  @Override
  public void draw(Canvas canvas) {
    if (isCanvasRectEmpty()) {
      return;
    }

    Paint paint = this.paint;

    // First of all, render the shadow.
    paint.reset();
    paint.setAntiAlias(true);
    paint.setColor(0x80000000);
    paint.setShadowLayer(shadowSize * 0.6f, shadowSize, shadowSize, 0xFF404040);
    canvas.drawRect(outerFrameRect, paint);

    // Draw the main part of the frame.
    if (shader.isPresent()) {
      paint.reset();
      paint.setAntiAlias(true);
      paint.setShader(shader.get());
      canvas.drawRect(outerFrameRect, paint);
    }

    // Draw the inner pane.
    paint.reset();
    paint.setAntiAlias(true);
    paint.setColor(0xFF000000);
    canvas.drawRect(innerFrameRect, paint);

    paint.setColor(innerPaneColor);
    paint.setMaskFilter(blurMaskFilter);
    canvas.drawRect(innerFrameRect, paint);

    // Draw the border.
    paint.reset();
    paint.setAntiAlias(true);
    paint.setColor(borderColor);
    paint.setStyle(Style.STROKE);

    canvas.drawRect(outerFrameRect, paint);
    canvas.drawRect(innerFrameRect, paint);
  }

  @Override
  protected void onBoundsChange(Rect bounds) {
    super.onBoundsChange(bounds);

    Rect canvasRect = getCanvasRect();

    outerFrameRect.set(canvasRect);
    innerFrameRect.set(
        canvasRect.left + frameWidth, canvasRect.top + frameWidth,
        canvasRect.right - frameWidth, canvasRect.bottom - frameWidth);
    shader = Optional.<Shader>of(new LinearGradient(
        0, canvasRect.top, 0, canvasRect.bottom, topColor, bottomColor, TileMode.CLAMP));
  }
}