diff options
Diffstat (limited to 'android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/Axis.java')
| -rw-r--r-- | android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/Axis.java | 337 |
1 files changed, 337 insertions, 0 deletions
diff --git a/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/Axis.java b/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/Axis.java new file mode 100644 index 000000000000..61407cb724cd --- /dev/null +++ b/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/Axis.java @@ -0,0 +1,337 @@ +/* -*- 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 android.util.Log; +import android.view.View; + +import org.mozilla.gecko.util.FloatUtils; + +import java.util.Map; + +/** + * 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 final float MS_PER_FRAME = 4.0f; + private static final float FRAMERATE_MULTIPLIER = (1000f/60f) / MS_PER_FRAME; + + // The values we use for friction are based on a 16.6ms frame, adjust them to MS_PER_FRAME: + // FRICTION^1 = FRICTION_ADJUSTED^(16/MS_PER_FRAME) + // FRICTION_ADJUSTED = e ^ ((ln(FRICTION))/FRAMERATE_MULTIPLIER) + static float getFrameAdjustedFriction(float baseFriction) { + return (float)Math.pow(Math.E, (Math.log(baseFriction) / FRAMERATE_MULTIPLIER)); + } + + static void setPrefs(Map<String, Integer> prefs) { + FRICTION_SLOW = getFrameAdjustedFriction(getFloatPref(prefs, PREF_SCROLLING_FRICTION_SLOW, 850)); + FRICTION_FAST = getFrameAdjustedFriction(getFloatPref(prefs, PREF_SCROLLING_FRICTION_FAST, 970)); + VELOCITY_THRESHOLD = 10 / FRAMERATE_MULTIPLIER; + MAX_EVENT_ACCELERATION = getFloatPref(prefs, PREF_SCROLLING_MAX_EVENT_ACCELERATION, 12); + OVERSCROLL_DECEL_RATE = getFrameAdjustedFriction(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 boolean mScrollingDisabled; /* Whether movement on this axis is locked. */ + private boolean mDisableSnap; /* Whether overscroll snapping is disabled. */ + private float mDisplacement; + + private FlingStates mFlingState; /* 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(); + + Axis(SubdocumentScrollHelper subscroller) { + mSubscroller = subscroller; + mOverscrollMode = View.OVER_SCROLL_IF_CONTENT_SCROLLS; + } + + 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; + } + + 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; + + // 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; + } + + void startFling(boolean stopped) { + mDisableSnap = mSubscroller.scrolling(); + + if (stopped) { + mFlingState = FlingStates.STOPPED; + } else { + mFlingState = FlingStates.FLINGING; + } + } + + /* Advances a fling animation by one step. */ + boolean advanceFling() { + 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 *= FRICTION_FAST; + } else { + float t = mVelocity / VELOCITY_THRESHOLD; + mVelocity *= FloatUtils.interpolate(FRICTION_SLOW, FRICTION_FAST, t); + } + } else { + // Otherwise, decrease the velocity linearly. + float elasticity = 1.0f - excess / (getViewportLength() * SNAP_LIMIT); + if (overscroll == Overscroll.MINUS) { + mVelocity = Math.min((mVelocity + OVERSCROLL_DECEL_RATE) * elasticity, 0.0f); + } else { // must be Overscroll.PLUS + mVelocity = Math.max((mVelocity - OVERSCROLL_DECEL_RATE) * 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; + + // 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 (getOverScrollMode() == View.OVER_SCROLL_NEVER) { + if (mDisplacement + getOrigin() < getPageStart()) { + mDisplacement = getPageStart() - getOrigin(); + stopFling(); + } else if (mDisplacement + getViewportEnd() > getPageEnd()) { + mDisplacement = getPageEnd() - getViewportEnd(); + stopFling(); + } + } + } + + float resetDisplacement() { + float d = mDisplacement; + mDisplacement = 0.0f; + return d; + } +} |