/* -*- 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.os.SystemClock; 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"; private static final String PREF_FLING_ACCEL_INTERVAL = "ui.scrolling.fling_accel_interval"; private static final String PREF_FLING_ACCEL_BASE_MULTIPLIER = "ui.scrolling.fling_accel_base_multiplier"; private static final String PREF_FLING_ACCEL_SUPPLEMENTAL_MULTIPLIER = "ui.scrolling.fling_accel_supplemental_multiplier"; private static final String PREF_FLING_CURVE_FUNCTION_X1 = "ui.scrolling.fling_curve_function_x1"; private static final String PREF_FLING_CURVE_FUNCTION_Y1 = "ui.scrolling.fling_curve_function_y1"; private static final String PREF_FLING_CURVE_FUNCTION_X2 = "ui.scrolling.fling_curve_function_x2"; private static final String PREF_FLING_CURVE_FUNCTION_Y2 = "ui.scrolling.fling_curve_function_y2"; private static final String PREF_FLING_CURVE_THRESHOLD_VELOCITY = "ui.scrolling.fling_curve_threshold_velocity"; private static final String PREF_FLING_CURVE_MAXIMUM_VELOCITY = "ui.scrolling.fling_curve_max_velocity"; private static final String PREF_FLING_CURVE_NEWTON_ITERATIONS = "ui.scrolling.fling_curve_newton_iterations"; // 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; // The interval within which if two flings are done then scrolling effect is accelerated. private static long FLING_ACCEL_INTERVAL; // The multiplication constant of the base velocity in case of accelerated scrolling. private static float FLING_ACCEL_BASE_MULTIPLIER; // The multiplication constant of the supplemental velocity in case of accelerated scrolling. private static float FLING_ACCEL_SUPPLEMENTAL_MULTIPLIER; // x co-ordinate of the second bezier control point private static float FLING_CURVE_FUNCTION_X1; // y co-ordinate of the second bezier control point private static float FLING_CURVE_FUNCTION_Y1; // x co-ordinate of the third bezier control point private static float FLING_CURVE_FUNCTION_X2; // y co-ordinate of the third bezier control point private static float FLING_CURVE_FUNCTION_Y2; // Minimum velocity for curve to be implemented i.e fling curving private static float FLING_CURVE_THRESHOLD_VELOCITY; // Maximum permitted velocity private static float FLING_CURVE_MAXIMUM_VELOCITY; // Number of iterations in the Newton-Raphson method private static int FLING_CURVE_NEWTON_ITERATIONS; private static float getFloatPref(Map prefs, String prefName, int defaultValue) { Integer value = (prefs == null ? null : prefs.get(prefName)); return (value == null || value < 0 ? defaultValue : value) / 1000f; } private static int getIntPref(Map 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, PREF_FLING_ACCEL_INTERVAL, PREF_FLING_ACCEL_BASE_MULTIPLIER, PREF_FLING_ACCEL_SUPPLEMENTAL_MULTIPLIER, PREF_FLING_CURVE_FUNCTION_X1, PREF_FLING_CURVE_FUNCTION_Y1, PREF_FLING_CURVE_FUNCTION_X2, PREF_FLING_CURVE_FUNCTION_Y2, PREF_FLING_CURVE_THRESHOLD_VELOCITY, PREF_FLING_CURVE_MAXIMUM_VELOCITY, PREF_FLING_CURVE_NEWTON_ITERATIONS }; PrefsHelper.getPrefs(prefs, new PrefsHelper.PrefHandlerBase() { Map mPrefs = new HashMap(); @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 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); FLING_ACCEL_INTERVAL = getIntPref(prefs, PREF_FLING_ACCEL_INTERVAL, 500); FLING_ACCEL_BASE_MULTIPLIER = getFloatPref(prefs, PREF_FLING_ACCEL_BASE_MULTIPLIER, 1000); FLING_ACCEL_SUPPLEMENTAL_MULTIPLIER = getFloatPref(prefs, PREF_FLING_ACCEL_SUPPLEMENTAL_MULTIPLIER, 1000); FLING_CURVE_FUNCTION_X1 = getFloatPref(prefs, PREF_FLING_CURVE_FUNCTION_X1, 410); FLING_CURVE_FUNCTION_Y1 = getFloatPref(prefs, PREF_FLING_CURVE_FUNCTION_Y1, 0); FLING_CURVE_FUNCTION_X2 = getFloatPref(prefs, PREF_FLING_CURVE_FUNCTION_X2, 800); FLING_CURVE_FUNCTION_Y2 = getFloatPref(prefs, PREF_FLING_CURVE_FUNCTION_Y2, 1000); FLING_CURVE_THRESHOLD_VELOCITY = getFloatPref(prefs, PREF_FLING_CURVE_THRESHOLD_VELOCITY, 30); FLING_CURVE_MAXIMUM_VELOCITY = getFloatPref(prefs, PREF_FLING_CURVE_MAXIMUM_VELOCITY, 70); FLING_CURVE_NEWTON_ITERATIONS = getIntPref(prefs, PREF_FLING_CURVE_NEWTON_ITERATIONS, 5); 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 final 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 long mLastFlingTime; private float mLastFlingVelocity; 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 getVisibleEndOfLayerView(); 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; } // Calculates and return the slope of the curve at given parameter t float getSlope(float t) { float y1 = FLING_CURVE_FUNCTION_Y1; float y2 = FLING_CURVE_FUNCTION_Y2; return (3 * y1) + t * (6 * y2 - 12 * y1) + t * t * (9 * y1 - 9 * y2 + 3); } // Calculates and returns the value of the bezier curve with the given parameter t and control points p1 and p2 float cubicBezier(float p1, float p2, float t) { return (3 * t * (1-t) * (1-t) * p1) + (3 * t * t * (1-t) * p2) + (t * t * t); } // Responsible for mapping the physical velocity to a the velocity obtained after applying bezier curve (with control points (X1,Y1) and (X2,Y2)) float flingCurve(float By) { int ni = FLING_CURVE_NEWTON_ITERATIONS; float[] guess = new float[ni]; float y1 = FLING_CURVE_FUNCTION_Y1; float y2 = FLING_CURVE_FUNCTION_Y2; guess[0] = By; for (int i = 1; i < ni; i++) { guess[i] = guess[i-1] - (cubicBezier(y1, y2, guess[i-1]) - By) / getSlope(guess[i-1]); } // guess[4] is the final approximate root the cubic equation. float t = guess[4]; float x1 = FLING_CURVE_FUNCTION_X1; float x2 = FLING_CURVE_FUNCTION_X2; return cubicBezier(x1, x2, t); } void updateWithTouchAt(float pos, float timeDelta) { float curveVelocityThreshold = FLING_CURVE_THRESHOLD_VELOCITY * GeckoAppShell.getDpi() * MS_PER_FRAME; float maxVelocity = FLING_CURVE_MAXIMUM_VELOCITY * GeckoAppShell.getDpi() * MS_PER_FRAME; float newVelocity = (mTouchPos - pos) / timeDelta * MS_PER_FRAME; if (Math.abs(newVelocity) > curveVelocityThreshold && Math.abs(newVelocity) < maxVelocity) { float sign = Math.signum(newVelocity); newVelocity = newVelocity * sign; float scale = maxVelocity - curveVelocityThreshold; float functInp = (newVelocity - curveVelocityThreshold) / scale; float functOut = flingCurve(functInp); newVelocity = functOut * scale + curveVelocityThreshold; newVelocity = newVelocity * sign; } 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; } // 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; } float accelerate(float velocity, float lastFlingVelocity){ return (FLING_ACCEL_BASE_MULTIPLIER * velocity + FLING_ACCEL_SUPPLEMENTAL_MULTIPLIER * lastFlingVelocity); } void startFling(boolean stopped) { mDisableSnap = mSubscroller.scrolling(); if (stopped) { mFlingState = FlingStates.STOPPED; } else { long now = SystemClock.uptimeMillis(); mVelocity = calculateFlingVelocity(); if ((now - mLastFlingTime < FLING_ACCEL_INTERVAL) && Math.signum(mVelocity) == Math.signum(mLastFlingVelocity)) { mVelocity = accelerate(mVelocity, mLastFlingVelocity); } mFlingState = FlingStates.FLINGING; mLastFlingVelocity = mVelocity; mLastFlingTime = now; } } /* 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()) { mDisplacement = getPageStart() - getOrigin(); } else if (mDisplacement + getOrigin() + getVisibleEndOfLayerView() > getPageEnd()) { mDisplacement = getPageEnd() - getOrigin() - getVisibleEndOfLayerView(); } // 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; } }