The Tor Browser: mobile/android/base/gfx/Axis.java@b8a032363ba2 (annotated)

mobile/android/base/gfx/Axis.java@b8a032363ba2 (annotated)

mobile/android/base/gfx/Axis.java

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 /* -*- Mode: Java; c-basic-offset: 4; tab-width: 20; indent-tabs-mode: nil; -*-
  * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 package org.mozilla.gecko.gfx;
 import java.util.HashMap;
 import java.util.Map;
 import org.mozilla.gecko.GeckoAppShell;
 import org.mozilla.gecko.PrefsHelper;
 import org.mozilla.gecko.util.FloatUtils;
 import android.util.Log;
 import android.view.View;
 /**
  * This class represents the physics for one axis of movement (i.e. either
  * horizontal or vertical). It tracks the different properties of movement
  * like displacement, velocity, viewport dimensions, etc. pertaining to
  * a particular axis.
  */
 abstract class Axis {
     private static final String LOGTAG = "GeckoAxis";
     private static final String PREF_SCROLLING_FRICTION_SLOW = "ui.scrolling.friction_slow";
     private static final String PREF_SCROLLING_FRICTION_FAST = "ui.scrolling.friction_fast";
     private static final String PREF_SCROLLING_MAX_EVENT_ACCELERATION = "ui.scrolling.max_event_acceleration";
     private static final String PREF_SCROLLING_OVERSCROLL_DECEL_RATE = "ui.scrolling.overscroll_decel_rate";
     private static final String PREF_SCROLLING_OVERSCROLL_SNAP_LIMIT = "ui.scrolling.overscroll_snap_limit";
     private static final String PREF_SCROLLING_MIN_SCROLLABLE_DISTANCE = "ui.scrolling.min_scrollable_distance";
     // This fraction of velocity remains after every animation frame when the velocity is low.
     private static float FRICTION_SLOW;
     // This fraction of velocity remains after every animation frame when the velocity is high.
     private static float FRICTION_FAST;
     // Below this velocity (in pixels per frame), the friction starts increasing from FRICTION_FAST
     // to FRICTION_SLOW.
     private static float VELOCITY_THRESHOLD;
     // The maximum velocity change factor between events, per ms, in %.
     // Direction changes are excluded.
     private static float MAX_EVENT_ACCELERATION;
     // The rate of deceleration when the surface has overscrolled.
     private static float OVERSCROLL_DECEL_RATE;
     // The percentage of the surface which can be overscrolled before it must snap back.
     private static float SNAP_LIMIT;
     // The minimum amount of space that must be present for an axis to be considered scrollable,
     // in pixels.
     private static float MIN_SCROLLABLE_DISTANCE;
     private static float getFloatPref(Map<String, Integer> prefs, String prefName, int defaultValue) {
         Integer value = (prefs == null ? null : prefs.get(prefName));
         return (float)(value == null || value < 0 ? defaultValue : value) / 1000f;
     }
     private static int getIntPref(Map<String, Integer> prefs, String prefName, int defaultValue) {
         Integer value = (prefs == null ? null : prefs.get(prefName));
         return (value == null || value < 0 ? defaultValue : value);
     }
     static void initPrefs() {
         final String[] prefs = { PREF_SCROLLING_FRICTION_FAST,
                                  PREF_SCROLLING_FRICTION_SLOW,
                                  PREF_SCROLLING_MAX_EVENT_ACCELERATION,
                                  PREF_SCROLLING_OVERSCROLL_DECEL_RATE,
                                  PREF_SCROLLING_OVERSCROLL_SNAP_LIMIT,
                                  PREF_SCROLLING_MIN_SCROLLABLE_DISTANCE };
         PrefsHelper.getPrefs(prefs, new PrefsHelper.PrefHandlerBase() {
             Map<String, Integer> mPrefs = new HashMap<String, Integer>();
             @Override public void prefValue(String name, int value) {
                 mPrefs.put(name, value);
             }
             @Override public void finish() {
                 setPrefs(mPrefs);
             }
         });
     }
     static final float MS_PER_FRAME = 1000.0f / 60.0f;
     static final long NS_PER_FRAME = Math.round(1000000000f / 60f);
     private static final float FRAMERATE_MULTIPLIER = (1000f/60f) / MS_PER_FRAME;
     private static final int FLING_VELOCITY_POINTS = 8;
     //  The values we use for friction are based on a 16.6ms frame, adjust them to currentNsPerFrame:
     static float getFrameAdjustedFriction(float baseFriction, long currentNsPerFrame) {
         float framerateMultiplier = (float)currentNsPerFrame / NS_PER_FRAME;
         return (float)Math.pow(Math.E, (Math.log(baseFriction) / framerateMultiplier));
     }
     static void setPrefs(Map<String, Integer> prefs) {
         FRICTION_SLOW = getFloatPref(prefs, PREF_SCROLLING_FRICTION_SLOW, 850);
         FRICTION_FAST = getFloatPref(prefs, PREF_SCROLLING_FRICTION_FAST, 970);
         VELOCITY_THRESHOLD = 10 / FRAMERATE_MULTIPLIER;
         MAX_EVENT_ACCELERATION = getFloatPref(prefs, PREF_SCROLLING_MAX_EVENT_ACCELERATION, GeckoAppShell.getDpi() > 300 ? 100 : 40);
         OVERSCROLL_DECEL_RATE = getFloatPref(prefs, PREF_SCROLLING_OVERSCROLL_DECEL_RATE, 40);
         SNAP_LIMIT = getFloatPref(prefs, PREF_SCROLLING_OVERSCROLL_SNAP_LIMIT, 300);
         MIN_SCROLLABLE_DISTANCE = getFloatPref(prefs, PREF_SCROLLING_MIN_SCROLLABLE_DISTANCE, 500);
         Log.i(LOGTAG, "Prefs: " + FRICTION_SLOW + "," + FRICTION_FAST + "," + VELOCITY_THRESHOLD + ","
                 + MAX_EVENT_ACCELERATION + "," + OVERSCROLL_DECEL_RATE + "," + SNAP_LIMIT + "," + MIN_SCROLLABLE_DISTANCE);
     }
     static {
         // set the scrolling parameters to default values on startup
         setPrefs(null);
     }
     private enum FlingStates {
         STOPPED,
         PANNING,
         FLINGING,
     }
     private enum Overscroll {
         NONE,
         MINUS,      // Overscrolled in the negative direction
         PLUS,       // Overscrolled in the positive direction
         BOTH,       // Overscrolled in both directions (page is zoomed to smaller than screen)
     }
     private final SubdocumentScrollHelper mSubscroller;
     private int mOverscrollMode; /* Default to only overscrolling if we're allowed to scroll in a direction */
     private float mFirstTouchPos;           /* Position of the first touch event on the current drag. */
     private float mTouchPos;                /* Position of the most recent touch event on the current drag. */
     private float mLastTouchPos;            /* Position of the touch event before touchPos. */
     private float mVelocity;                /* Velocity in this direction; pixels per animation frame. */
     private float[] mRecentVelocities;      /* Circular buffer of recent velocities since last touch start. */
     private int mRecentVelocityCount;       /* Number of values put into mRecentVelocities (unbounded). */
     private boolean mScrollingDisabled;     /* Whether movement on this axis is locked. */
     private boolean mDisableSnap;           /* Whether overscroll snapping is disabled. */
     private float mDisplacement;
     private FlingStates mFlingState = FlingStates.STOPPED; /* The fling state we're in on this axis. */
     protected abstract float getOrigin();
     protected abstract float getViewportLength();
     protected abstract float getPageStart();
     protected abstract float getPageLength();
     protected abstract float getMarginStart();
     protected abstract float getMarginEnd();
     protected abstract boolean marginsHidden();
     Axis(SubdocumentScrollHelper subscroller) {
         mSubscroller = subscroller;
         mOverscrollMode = View.OVER_SCROLL_IF_CONTENT_SCROLLS;
         mRecentVelocities = new float[FLING_VELOCITY_POINTS];
     }
     // Implementors can override these to show effects when the axis overscrolls
     protected void overscrollFling(float velocity) { }
     protected void overscrollPan(float displacement) { }
     public void setOverScrollMode(int overscrollMode) {
         mOverscrollMode = overscrollMode;
     }
     public int getOverScrollMode() {
         return mOverscrollMode;
     }
     private float getViewportEnd() {
         return getOrigin() + getViewportLength();
     }
     private float getPageEnd() {
         return getPageStart() + getPageLength();
     }
     void startTouch(float pos) {
         mVelocity = 0.0f;
         mScrollingDisabled = false;
         mFirstTouchPos = mTouchPos = mLastTouchPos = pos;
         mRecentVelocityCount = 0;
     }
     float panDistance(float currentPos) {
         return currentPos - mFirstTouchPos;
     }
     void setScrollingDisabled(boolean disabled) {
         mScrollingDisabled = disabled;
     }
     void saveTouchPos() {
         mLastTouchPos = mTouchPos;
     }
     void updateWithTouchAt(float pos, float timeDelta) {
         float newVelocity = (mTouchPos - pos) / timeDelta * MS_PER_FRAME;
         mRecentVelocities[mRecentVelocityCount % FLING_VELOCITY_POINTS] = newVelocity;
         mRecentVelocityCount++;
         // If there's a direction change, or current velocity is very low,
         // allow setting of the velocity outright. Otherwise, use the current
         // velocity and a maximum change factor to set the new velocity.
         boolean curVelocityIsLow = Math.abs(mVelocity) < 1.0f / FRAMERATE_MULTIPLIER;
         boolean directionChange = (mVelocity > 0) != (newVelocity > 0);
         if (curVelocityIsLow || (directionChange && !FloatUtils.fuzzyEquals(newVelocity, 0.0f))) {
             mVelocity = newVelocity;
         } else {
             float maxChange = Math.abs(mVelocity * timeDelta * MAX_EVENT_ACCELERATION);
             mVelocity = Math.min(mVelocity + maxChange, Math.max(mVelocity - maxChange, newVelocity));
         }
         mTouchPos = pos;
     }
     boolean overscrolled() {
         return getOverscroll() != Overscroll.NONE;
     }
     private Overscroll getOverscroll() {
         boolean minus = (getOrigin() < getPageStart());
         boolean plus = (getViewportEnd() > getPageEnd());
         if (minus && plus) {
             return Overscroll.BOTH;
         } else if (minus) {
             return Overscroll.MINUS;
         } else if (plus) {
             return Overscroll.PLUS;
         } else {
             return Overscroll.NONE;
         }
     }
     // Returns the amount that the page has been overscrolled. If the page hasn't been
     // overscrolled on this axis, returns 0.
     private float getExcess() {
         switch (getOverscroll()) {
         case MINUS:     return getPageStart() - getOrigin();
         case PLUS:      return getViewportEnd() - getPageEnd();
         case BOTH:      return (getViewportEnd() - getPageEnd()) + (getPageStart() - getOrigin());
         default:        return 0.0f;
         }
     }
     /*
      * Returns true if the page is zoomed in to some degree along this axis such that scrolling is
      * possible and this axis has not been scroll locked while panning. Otherwise, returns false.
      */
     boolean scrollable() {
         // If we're scrolling a subdocument, ignore the viewport length restrictions (since those
         // apply to the top-level document) and only take into account axis locking.
         if (mSubscroller.scrolling()) {
             return !mScrollingDisabled;
         }
         // if we are axis locked, return false
         if (mScrollingDisabled) {
             return false;
         }
         // if there are margins on this axis but they are currently hidden,
         // we must be able to scroll in order to make them visible, so allow
         // scrolling in that case
         if (marginsHidden()) {
             return true;
         }
         // there is scrollable space, and we're not disabled, or the document fits the viewport
         // but we always allow overscroll anyway
         return getViewportLength() <= getPageLength() - MIN_SCROLLABLE_DISTANCE ||
                getOverScrollMode() == View.OVER_SCROLL_ALWAYS;
     }
     /*
      * Returns the resistance, as a multiplier, that should be taken into account when
      * tracking or pinching.
      */
     float getEdgeResistance(boolean forPinching) {
         float excess = getExcess();
         if (excess > 0.0f && (getOverscroll() == Overscroll.BOTH || !forPinching)) {
             // excess can be greater than viewport length, but the resistance
             // must never drop below 0.0
             return Math.max(0.0f, SNAP_LIMIT - excess / getViewportLength());
         }
         return 1.0f;
     }
     /* Returns the velocity. If the axis is locked, returns 0. */
     float getRealVelocity() {
         return scrollable() ? mVelocity : 0f;
     }
     void startPan() {
         mFlingState = FlingStates.PANNING;
     }
     private float calculateFlingVelocity() {
         int usablePoints = Math.min(mRecentVelocityCount, FLING_VELOCITY_POINTS);
         if (usablePoints <= 1) {
             return mVelocity;
         }
         float average = 0;
         for (int i = 0; i < usablePoints; i++) {
             average += mRecentVelocities[i];
         }
         return average / usablePoints;
     }
     void startFling(boolean stopped) {
         mDisableSnap = mSubscroller.scrolling();
         if (stopped) {
             mFlingState = FlingStates.STOPPED;
         } else {
             mVelocity = calculateFlingVelocity();
             mFlingState = FlingStates.FLINGING;
         }
     }
     /* Advances a fling animation by one step. */
     boolean advanceFling(long realNsPerFrame) {
         if (mFlingState != FlingStates.FLINGING) {
             return false;
         }
         if (mSubscroller.scrolling() && !mSubscroller.lastScrollSucceeded()) {
             // if the subdocument stopped scrolling, it's because it reached the end
             // of the subdocument. we don't do overscroll on subdocuments, so there's
             // no point in continuing this fling.
             return false;
         }
         float excess = getExcess();
         Overscroll overscroll = getOverscroll();
         boolean decreasingOverscroll = false;
         if ((overscroll == Overscroll.MINUS && mVelocity > 0) ||
             (overscroll == Overscroll.PLUS && mVelocity < 0))
         {
             decreasingOverscroll = true;
         }
         if (mDisableSnap || FloatUtils.fuzzyEquals(excess, 0.0f) || decreasingOverscroll) {
             // If we aren't overscrolled, just apply friction.
             if (Math.abs(mVelocity) >= VELOCITY_THRESHOLD) {
                 mVelocity *= getFrameAdjustedFriction(FRICTION_FAST, realNsPerFrame);
             } else {
                 float t = mVelocity / VELOCITY_THRESHOLD;
                 mVelocity *= FloatUtils.interpolate(getFrameAdjustedFriction(FRICTION_SLOW, realNsPerFrame),
                                                     getFrameAdjustedFriction(FRICTION_FAST, realNsPerFrame), t);
             }
         } else {
             // Otherwise, decrease the velocity linearly.
             float elasticity = 1.0f - excess / (getViewportLength() * SNAP_LIMIT);
             float overscrollDecelRate = getFrameAdjustedFriction(OVERSCROLL_DECEL_RATE, realNsPerFrame);
             if (overscroll == Overscroll.MINUS) {
                 mVelocity = Math.min((mVelocity + overscrollDecelRate) * elasticity, 0.0f);
             } else { // must be Overscroll.PLUS
                 mVelocity = Math.max((mVelocity - overscrollDecelRate) * elasticity, 0.0f);
             }
         }
         return true;
     }
     void stopFling() {
         mVelocity = 0.0f;
         mFlingState = FlingStates.STOPPED;
     }
     // Performs displacement of the viewport position according to the current velocity.
     void displace() {
         // if this isn't scrollable just return
         if (!scrollable())
             return;
         if (mFlingState == FlingStates.PANNING)
             mDisplacement += (mLastTouchPos - mTouchPos) * getEdgeResistance(false);
         else
             mDisplacement += mVelocity * getEdgeResistance(false);
         // if overscroll is disabled and we're trying to overscroll, reset the displacement
         // to remove any excess. Using getExcess alone isn't enough here since it relies on
         // getOverscroll which doesn't take into account any new displacment being applied.
         // If we using a subscroller, we don't want to alter the scrolling being done
         if (getOverScrollMode() == View.OVER_SCROLL_NEVER && !mSubscroller.scrolling()) {
             float originalDisplacement = mDisplacement;
             if (mDisplacement + getOrigin() < getPageStart() - getMarginStart()) {
                 mDisplacement = getPageStart() - getMarginStart() - getOrigin();
             } else if (mDisplacement + getViewportEnd() > getPageEnd() + getMarginEnd()) {
                 mDisplacement = getPageEnd() - getMarginEnd() - getViewportEnd();
             }
             // Return the amount of overscroll so that the overscroll controller can draw it for us
             if (originalDisplacement != mDisplacement) {
                 if (mFlingState == FlingStates.FLINGING) {
                     overscrollFling(mVelocity / MS_PER_FRAME * 1000);
                     stopFling();
                 } else if (mFlingState == FlingStates.PANNING) {
                     overscrollPan(originalDisplacement - mDisplacement);
                 }
             }
         }
     }
     float resetDisplacement() {
         float d = mDisplacement;
         mDisplacement = 0.0f;
         return d;
     }
     void setAutoscrollVelocity(float velocity) {
         if (mFlingState != FlingStates.STOPPED) {
             Log.e(LOGTAG, "Setting autoscroll velocity while in a fling is not allowed!");
             return;
         }
         mVelocity = velocity;
     }
 }

The Tor Browser / annotate

mobile/android/base/gfx/Axis.java@b8a032363ba2 (annotated)

mobile/android/base/gfx/Axis.java