The Tor Browser: comparison mobile/android/base/gfx/Axis.java

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+:b9d8f6ddf012
+/* -*- 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 / file comparison

comparison: mobile/android/base/gfx/Axis.java

mobile/android/base/gfx/Axis.java