[Paint Preview] Create viewport class

This CL replaces the viewport state in PlayerFrameMediator with a new
PlayerFrameViewport class for managing state.

This causes a chain reaction requiring
1. A number of new method calls.
2. Removal of scale updates from moveViewport
3. Removal of scale maps for storing bitmaps

Bug: 1099722
Change-Id: Ia666485b59b0808af20055a1c023eb9e5176ecf5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2285257Reviewed-by: Mehran Mahmoudi <mahmoudi@chromium.org>
Commit-Queue: Calder Kitagawa <ckitagawa@chromium.org>
Cr-Commit-Position: refs/heads/master@{#786428}

components/paint_preview/player/android/BUILD.gn

@@ -62,6 +62,7 @@ android_library("java") {
     "java/src/org/chromium/components/paintpreview/player/frame/PlayerFrameView.java",
     "java/src/org/chromium/components/paintpreview/player/frame/PlayerFrameViewBinder.java",
     "java/src/org/chromium/components/paintpreview/player/frame/PlayerFrameViewDelegate.java",
+    "java/src/org/chromium/components/paintpreview/player/frame/PlayerFrameViewport.java",
   ]
 
   deps = [

components/paint_preview/player/android/java/src/org/chromium/components/paintpreview/player/frame/PlayerFrameViewport.java

+// Copyright 2020 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.components.paintpreview.player.frame;
+
+import android.graphics.Matrix;
+import android.graphics.Rect;
+import android.util.Size;
+
+import androidx.annotation.VisibleForTesting;
+
+/**
+ * Used to represent the viewport for a frame in the paint preview player. There should be one of
+ * these objects per player frame and it should be shared between various classes that manipulated
+ * the location. Should only be accessed on the UI thread to avoid the need for locks.
+ */
+public class PlayerFrameViewport {
+    /** The size of the viewport. */
+    private Size mViewportSize;
+    /** A 3x3 affine transformation matrix to track scale and translation. */
+    @VisibleForTesting
+    final Matrix mViewportTransform;
+    /** Transient storage objects to avoid allocations. */
+    private final Rect mViewportRect = new Rect();
+    private final float[] mMatrixValues = new float[9];
+
+    PlayerFrameViewport(Size size, Matrix matrix) {
+        mViewportSize = size;
+        mViewportTransform = matrix;
+    }
+
+    /**
+     * @return the width of the viewport.
+     */
+    int getWidth() {
+        return mViewportSize.getWidth();
+    }
+
+    /**
+     * @return the height of the viewport.
+     */
+    int getHeight() {
+        return mViewportSize.getHeight();
+    }
+
+    /**
+     * Returns the size of the viewport. Use with caution as the values of the returned object are
+     * not updated.
+     * @return the size of the viewport.
+     */
+    Size getSize() {
+        return mViewportSize;
+    }
+
+    /**
+     * Returns the translation of the viewport in the X direction (AKA left).
+     * @return the x translation of the viewport.
+     */
+    float getTransX() {
+        mViewportTransform.getValues(mMatrixValues);
+        return mMatrixValues[Matrix.MTRANS_X];
+    }
+
+    /**
+     * Returns the translation of the viewport in the Y direction (AKA top).
+     * @return the y translation of the viewport.
+     */
+    float getTransY() {
+        mViewportTransform.getValues(mMatrixValues);
+        return mMatrixValues[Matrix.MTRANS_Y];
+    }
+
+    /**
+     * Returns the scale at which to show contents.
+     * @return a scale factor for the viewport.
+     */
+    float getScale() {
+        mViewportTransform.getValues(mMatrixValues);
+        return mMatrixValues[Matrix.MSCALE_X]; // x and y should be identical here.
+    }
+
+    /**
+     * Returns the current viewport position as a rect. Use cautiously as this is an instantaneous
+     * snapshot and is not continually updated.
+     * @return a rect of the current viewport.
+     * */
+    Rect asRect() {
+        mViewportTransform.getValues(mMatrixValues);
+        final int left = Math.round(mMatrixValues[Matrix.MTRANS_X]);
+        final int top = Math.round(mMatrixValues[Matrix.MTRANS_Y]);
+        mViewportRect.set(
+                left, top, left + mViewportSize.getWidth(), top + mViewportSize.getHeight());
+        return mViewportRect;
+    }
+
+    /**
+     * Sets the size of the viewport.
+     * @param width The width of the viewport.
+     * @param height The height of the viewport.
+     */
+    void setSize(int width, int height) {
+        mViewportSize = new Size(width, height);
+    }
+
+    /**
+     * Sets the position x, y (left, top) of the viewport.
+     * @param x The left side of the viewport.
+     * @param y The top of the viewport.
+     */
+    void setTrans(float x, float y) {
+        mViewportTransform.getValues(mMatrixValues);
+        mMatrixValues[Matrix.MTRANS_X] = x;
+        mMatrixValues[Matrix.MTRANS_Y] = y;
+        mViewportTransform.setValues(mMatrixValues);
+    }
+
+    /**
+     * Sets the scale of the viewport.
+     * @param scaleFactor The scale of the viewport.
+     */
+    void setScale(float scaleFactor) {
+        mViewportTransform.getValues(mMatrixValues);
+        mMatrixValues[Matrix.MSCALE_X] = scaleFactor;
+        mMatrixValues[Matrix.MSCALE_Y] = scaleFactor;
+        mViewportTransform.setValues(mMatrixValues);
+    }
+
+    /**
+     * Offsets/shifts the viewport by a set amount.
+     * @param dx The distance to offset on the x-axis.
+     * @param dy The distance to offset on the y-axis.
+     */
+    void offset(float dx, float dy) {
+        mViewportTransform.postTranslate(dx, dy);
+    }
+
+    /**
+     * Affine scaling of the viewport about a focal point/pivot.
+     * @param scaleFactor The amount to scale by (relative to the current scale).
+     * @param focalX The x-coordinate of the focal point.
+     * @param focalY The y-coordinate of the focal point.
+     */
+    void scale(float scaleFactor, float focalX, float focalY) {
+        mViewportTransform.postScale(scaleFactor, scaleFactor, -focalX, -focalY);
+    }
+}