[Remoting Android] Define feedback animation size in dp

remoting/android/java/src/org/chromium/chromoting/FeedbackAnimator.java

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.chromoting;
 
 import android.graphics.Color;
 import android.graphics.Paint;
 import android.graphics.Point;
 import android.graphics.RadialGradient;
 import android.graphics.Shader;
 import android.os.SystemClock;
+import android.view.View;
 
 /** Helper class for displaying the press feedback animations. */
 public final class FeedbackAnimator
         implements Event.ParameterCallback<Boolean, PaintEventParameter> {
     /** Total duration of the animation, in milliseconds. */
     private static final float TOTAL_DURATION_MS = 220;
 
+    private static float sSmallFeedbackPixelRadius = -1;
+    private static float sLargeFeedbackPixelRadius = -1;
+
     /** Start time of the animation, from {@link SystemClock#uptimeMillis()}. */
     private final long mStartTimeInMs;
 
     /** Contains the size of the feedback animation for the most recent request. */
     private final float mFeedbackSizeInPixels;
 
     private final Paint mPaint = new Paint();
 
     private final Point mPos;
 
     private FeedbackAnimator(float feedbackSizeInPixels, Point pos) {
         mStartTimeInMs = SystemClock.uptimeMillis();
         mFeedbackSizeInPixels = feedbackSizeInPixels;
         mPos = pos;
     }
 
     /** Begins a new animation sequence at position (|pos|). */
     public static void startAnimation(DesktopView view,
                                       Point pos,
                                       DesktopView.InputFeedbackType feedbackType) {
         if (feedbackType == DesktopView.InputFeedbackType.NONE) {
             return;
         }
 
         view.onPaint().addSelfRemovable(new FeedbackAnimator(
-                getInputFeedbackSizeInPixels(feedbackType), pos));
+                getInputFeedbackSizeInPixels(feedbackType, view), pos));
     }
 
-    private static float getInputFeedbackSizeInPixels(DesktopView.InputFeedbackType feedbackType) {
+    private static float getInputFeedbackSizeInPixels(DesktopView.InputFeedbackType feedbackType,
+                                                      View view) {

[Lambros, 2016/07/25 22:14:32]

I think it's more idiomatic to pass a Context rather than a View ?

         switch (feedbackType) {
             case SMALL_ANIMATION:
-                return 40.0f;
+                if (sSmallFeedbackPixelRadius < 0) {
+                    sSmallFeedbackPixelRadius = view.getResources()
+                            .getDimensionPixelSize(R.dimen.feedback_animation_radius_small);

[Lambros, 2016/07/25 22:14:32]

The dp/pixel scaling factor is dependent on the Context which is tied to the
Activity lifecycle, I think. So you need some way of invalidating the cache if
the Activity is destroyed/re-created (for example, if a new display is
hot-plugged?)

If you keep a cache of the values, it's probably better to store the cache
inside an Activity or an Activity-owned object. A static member is probably not
the right thing?

Also, if the cache is stored in an Activity, you could simply initialize the
values in onCreate() so you wouldn't need the '< 0' logic.

[Lambros, 2016/07/25 22:28:45]

Actually, I'm not sure about this. The scaling factor (from Android's
DisplayMetrics class) might be global and not hot-pluggable. It might be
different for different displays, if you can have more than one. I'm not sure.

+                }
+                return sSmallFeedbackPixelRadius;
 
             case LARGE_ANIMATION:
-                return 160.0f;
+                if (sLargeFeedbackPixelRadius < 0) {
+                    sLargeFeedbackPixelRadius = view.getResources()
+                            .getDimensionPixelSize(R.dimen.feedback_animation_radius_large);
+                }
+                return sLargeFeedbackPixelRadius;
 
             default:
                 // Unreachable, but required by Google Java style and findbugs.
                 assert false : "Unreached";
                 return 0.0f;
         }
     }
 
     @Override
     public Boolean run(PaintEventParameter parameter) {
@@ skipping 19 matching lines @@
         int transparentBlack = Color.argb(0, 0, 0, 0);
         int white = Color.argb(alpha, 0xff, 0xff, 0xff);
         int black = Color.argb(alpha, 0, 0, 0);
         mPaint.setShader(new RadialGradient(mPos.x, mPos.y, radius,
                 new int[] {transparentBlack, white, black, transparentBlack},
                 new float[] {0.0f, 0.8f, 0.9f, 1.0f}, Shader.TileMode.CLAMP));
         parameter.canvas.drawCircle(mPos.x, mPos.y, radius, mPaint);
         return true;
     }
 }