mobile/android/base/gfx/Axis.java@6474c204b198
mobile/android/base/gfx/Axis.java
Wed, 31 Dec 2014 06:09:35 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Wed, 31 Dec 2014 06:09:35 +0100
- changeset 0
- 6474c204b198
- permissions
- -rw-r--r--
Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.
1 /* -*- Mode: Java; c-basic-offset: 4; tab-width: 20; indent-tabs-mode: nil; -*-
2 * This Source Code Form is subject to the terms of the Mozilla Public
3 * License, v. 2.0. If a copy of the MPL was not distributed with this
4 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
6 package org.mozilla.gecko.gfx;
8 import java.util.HashMap;
9 import java.util.Map;
11 import org.mozilla.gecko.GeckoAppShell;
12 import org.mozilla.gecko.PrefsHelper;
13 import org.mozilla.gecko.util.FloatUtils;
15 import android.util.Log;
16 import android.view.View;
18 /**
19 * This class represents the physics for one axis of movement (i.e. either
20 * horizontal or vertical). It tracks the different properties of movement
21 * like displacement, velocity, viewport dimensions, etc. pertaining to
22 * a particular axis.
23 */
24 abstract class Axis {
25 private static final String LOGTAG = "GeckoAxis";
27 private static final String PREF_SCROLLING_FRICTION_SLOW = "ui.scrolling.friction_slow";
28 private static final String PREF_SCROLLING_FRICTION_FAST = "ui.scrolling.friction_fast";
29 private static final String PREF_SCROLLING_MAX_EVENT_ACCELERATION = "ui.scrolling.max_event_acceleration";
30 private static final String PREF_SCROLLING_OVERSCROLL_DECEL_RATE = "ui.scrolling.overscroll_decel_rate";
31 private static final String PREF_SCROLLING_OVERSCROLL_SNAP_LIMIT = "ui.scrolling.overscroll_snap_limit";
32 private static final String PREF_SCROLLING_MIN_SCROLLABLE_DISTANCE = "ui.scrolling.min_scrollable_distance";
34 // This fraction of velocity remains after every animation frame when the velocity is low.
35 private static float FRICTION_SLOW;
36 // This fraction of velocity remains after every animation frame when the velocity is high.
37 private static float FRICTION_FAST;
38 // Below this velocity (in pixels per frame), the friction starts increasing from FRICTION_FAST
39 // to FRICTION_SLOW.
40 private static float VELOCITY_THRESHOLD;
41 // The maximum velocity change factor between events, per ms, in %.
42 // Direction changes are excluded.
43 private static float MAX_EVENT_ACCELERATION;
45 // The rate of deceleration when the surface has overscrolled.
46 private static float OVERSCROLL_DECEL_RATE;
47 // The percentage of the surface which can be overscrolled before it must snap back.
48 private static float SNAP_LIMIT;
50 // The minimum amount of space that must be present for an axis to be considered scrollable,
51 // in pixels.
52 private static float MIN_SCROLLABLE_DISTANCE;
54 private static float getFloatPref(Map<String, Integer> prefs, String prefName, int defaultValue) {
55 Integer value = (prefs == null ? null : prefs.get(prefName));
56 return (float)(value == null || value < 0 ? defaultValue : value) / 1000f;
57 }
59 private static int getIntPref(Map<String, Integer> prefs, String prefName, int defaultValue) {
60 Integer value = (prefs == null ? null : prefs.get(prefName));
61 return (value == null || value < 0 ? defaultValue : value);
62 }
64 static void initPrefs() {
65 final String[] prefs = { PREF_SCROLLING_FRICTION_FAST,
66 PREF_SCROLLING_FRICTION_SLOW,
67 PREF_SCROLLING_MAX_EVENT_ACCELERATION,
68 PREF_SCROLLING_OVERSCROLL_DECEL_RATE,
69 PREF_SCROLLING_OVERSCROLL_SNAP_LIMIT,
70 PREF_SCROLLING_MIN_SCROLLABLE_DISTANCE };
72 PrefsHelper.getPrefs(prefs, new PrefsHelper.PrefHandlerBase() {
73 Map<String, Integer> mPrefs = new HashMap<String, Integer>();
75 @Override public void prefValue(String name, int value) {
76 mPrefs.put(name, value);
77 }
79 @Override public void finish() {
80 setPrefs(mPrefs);
81 }
82 });
83 }
85 static final float MS_PER_FRAME = 1000.0f / 60.0f;
86 static final long NS_PER_FRAME = Math.round(1000000000f / 60f);
87 private static final float FRAMERATE_MULTIPLIER = (1000f/60f) / MS_PER_FRAME;
88 private static final int FLING_VELOCITY_POINTS = 8;
90 // The values we use for friction are based on a 16.6ms frame, adjust them to currentNsPerFrame:
91 static float getFrameAdjustedFriction(float baseFriction, long currentNsPerFrame) {
92 float framerateMultiplier = (float)currentNsPerFrame / NS_PER_FRAME;
93 return (float)Math.pow(Math.E, (Math.log(baseFriction) / framerateMultiplier));
94 }
96 static void setPrefs(Map<String, Integer> prefs) {
97 FRICTION_SLOW = getFloatPref(prefs, PREF_SCROLLING_FRICTION_SLOW, 850);
98 FRICTION_FAST = getFloatPref(prefs, PREF_SCROLLING_FRICTION_FAST, 970);
99 VELOCITY_THRESHOLD = 10 / FRAMERATE_MULTIPLIER;
100 MAX_EVENT_ACCELERATION = getFloatPref(prefs, PREF_SCROLLING_MAX_EVENT_ACCELERATION, GeckoAppShell.getDpi() > 300 ? 100 : 40);
101 OVERSCROLL_DECEL_RATE = getFloatPref(prefs, PREF_SCROLLING_OVERSCROLL_DECEL_RATE, 40);
102 SNAP_LIMIT = getFloatPref(prefs, PREF_SCROLLING_OVERSCROLL_SNAP_LIMIT, 300);
103 MIN_SCROLLABLE_DISTANCE = getFloatPref(prefs, PREF_SCROLLING_MIN_SCROLLABLE_DISTANCE, 500);
104 Log.i(LOGTAG, "Prefs: " + FRICTION_SLOW + "," + FRICTION_FAST + "," + VELOCITY_THRESHOLD + ","
105 + MAX_EVENT_ACCELERATION + "," + OVERSCROLL_DECEL_RATE + "," + SNAP_LIMIT + "," + MIN_SCROLLABLE_DISTANCE);
106 }
108 static {
109 // set the scrolling parameters to default values on startup
110 setPrefs(null);
111 }
113 private enum FlingStates {
114 STOPPED,
115 PANNING,
116 FLINGING,
117 }
119 private enum Overscroll {
120 NONE,
121 MINUS, // Overscrolled in the negative direction
122 PLUS, // Overscrolled in the positive direction
123 BOTH, // Overscrolled in both directions (page is zoomed to smaller than screen)
124 }
126 private final SubdocumentScrollHelper mSubscroller;
128 private int mOverscrollMode; /* Default to only overscrolling if we're allowed to scroll in a direction */
129 private float mFirstTouchPos; /* Position of the first touch event on the current drag. */
130 private float mTouchPos; /* Position of the most recent touch event on the current drag. */
131 private float mLastTouchPos; /* Position of the touch event before touchPos. */
132 private float mVelocity; /* Velocity in this direction; pixels per animation frame. */
133 private float[] mRecentVelocities; /* Circular buffer of recent velocities since last touch start. */
134 private int mRecentVelocityCount; /* Number of values put into mRecentVelocities (unbounded). */
135 private boolean mScrollingDisabled; /* Whether movement on this axis is locked. */
136 private boolean mDisableSnap; /* Whether overscroll snapping is disabled. */
137 private float mDisplacement;
139 private FlingStates mFlingState = FlingStates.STOPPED; /* The fling state we're in on this axis. */
141 protected abstract float getOrigin();
142 protected abstract float getViewportLength();
143 protected abstract float getPageStart();
144 protected abstract float getPageLength();
145 protected abstract float getMarginStart();
146 protected abstract float getMarginEnd();
147 protected abstract boolean marginsHidden();
149 Axis(SubdocumentScrollHelper subscroller) {
150 mSubscroller = subscroller;
151 mOverscrollMode = View.OVER_SCROLL_IF_CONTENT_SCROLLS;
152 mRecentVelocities = new float[FLING_VELOCITY_POINTS];
153 }
155 // Implementors can override these to show effects when the axis overscrolls
156 protected void overscrollFling(float velocity) { }
157 protected void overscrollPan(float displacement) { }
159 public void setOverScrollMode(int overscrollMode) {
160 mOverscrollMode = overscrollMode;
161 }
163 public int getOverScrollMode() {
164 return mOverscrollMode;
165 }
167 private float getViewportEnd() {
168 return getOrigin() + getViewportLength();
169 }
171 private float getPageEnd() {
172 return getPageStart() + getPageLength();
173 }
175 void startTouch(float pos) {
176 mVelocity = 0.0f;
177 mScrollingDisabled = false;
178 mFirstTouchPos = mTouchPos = mLastTouchPos = pos;
179 mRecentVelocityCount = 0;
180 }
182 float panDistance(float currentPos) {
183 return currentPos - mFirstTouchPos;
184 }
186 void setScrollingDisabled(boolean disabled) {
187 mScrollingDisabled = disabled;
188 }
190 void saveTouchPos() {
191 mLastTouchPos = mTouchPos;
192 }
194 void updateWithTouchAt(float pos, float timeDelta) {
195 float newVelocity = (mTouchPos - pos) / timeDelta * MS_PER_FRAME;
197 mRecentVelocities[mRecentVelocityCount % FLING_VELOCITY_POINTS] = newVelocity;
198 mRecentVelocityCount++;
200 // If there's a direction change, or current velocity is very low,
201 // allow setting of the velocity outright. Otherwise, use the current
202 // velocity and a maximum change factor to set the new velocity.
203 boolean curVelocityIsLow = Math.abs(mVelocity) < 1.0f / FRAMERATE_MULTIPLIER;
204 boolean directionChange = (mVelocity > 0) != (newVelocity > 0);
205 if (curVelocityIsLow || (directionChange && !FloatUtils.fuzzyEquals(newVelocity, 0.0f))) {
206 mVelocity = newVelocity;
207 } else {
208 float maxChange = Math.abs(mVelocity * timeDelta * MAX_EVENT_ACCELERATION);
209 mVelocity = Math.min(mVelocity + maxChange, Math.max(mVelocity - maxChange, newVelocity));
210 }
212 mTouchPos = pos;
213 }
215 boolean overscrolled() {
216 return getOverscroll() != Overscroll.NONE;
217 }
219 private Overscroll getOverscroll() {
220 boolean minus = (getOrigin() < getPageStart());
221 boolean plus = (getViewportEnd() > getPageEnd());
222 if (minus && plus) {
223 return Overscroll.BOTH;
224 } else if (minus) {
225 return Overscroll.MINUS;
226 } else if (plus) {
227 return Overscroll.PLUS;
228 } else {
229 return Overscroll.NONE;
230 }
231 }
233 // Returns the amount that the page has been overscrolled. If the page hasn't been
234 // overscrolled on this axis, returns 0.
235 private float getExcess() {
236 switch (getOverscroll()) {
237 case MINUS: return getPageStart() - getOrigin();
238 case PLUS: return getViewportEnd() - getPageEnd();
239 case BOTH: return (getViewportEnd() - getPageEnd()) + (getPageStart() - getOrigin());
240 default: return 0.0f;
241 }
242 }
244 /*
245 * Returns true if the page is zoomed in to some degree along this axis such that scrolling is
246 * possible and this axis has not been scroll locked while panning. Otherwise, returns false.
247 */
248 boolean scrollable() {
249 // If we're scrolling a subdocument, ignore the viewport length restrictions (since those
250 // apply to the top-level document) and only take into account axis locking.
251 if (mSubscroller.scrolling()) {
252 return !mScrollingDisabled;
253 }
255 // if we are axis locked, return false
256 if (mScrollingDisabled) {
257 return false;
258 }
260 // if there are margins on this axis but they are currently hidden,
261 // we must be able to scroll in order to make them visible, so allow
262 // scrolling in that case
263 if (marginsHidden()) {
264 return true;
265 }
267 // there is scrollable space, and we're not disabled, or the document fits the viewport
268 // but we always allow overscroll anyway
269 return getViewportLength() <= getPageLength() - MIN_SCROLLABLE_DISTANCE ||
270 getOverScrollMode() == View.OVER_SCROLL_ALWAYS;
271 }
273 /*
274 * Returns the resistance, as a multiplier, that should be taken into account when
275 * tracking or pinching.
276 */
277 float getEdgeResistance(boolean forPinching) {
278 float excess = getExcess();
279 if (excess > 0.0f && (getOverscroll() == Overscroll.BOTH || !forPinching)) {
280 // excess can be greater than viewport length, but the resistance
281 // must never drop below 0.0
282 return Math.max(0.0f, SNAP_LIMIT - excess / getViewportLength());
283 }
284 return 1.0f;
285 }
287 /* Returns the velocity. If the axis is locked, returns 0. */
288 float getRealVelocity() {
289 return scrollable() ? mVelocity : 0f;
290 }
292 void startPan() {
293 mFlingState = FlingStates.PANNING;
294 }
296 private float calculateFlingVelocity() {
297 int usablePoints = Math.min(mRecentVelocityCount, FLING_VELOCITY_POINTS);
298 if (usablePoints <= 1) {
299 return mVelocity;
300 }
301 float average = 0;
302 for (int i = 0; i < usablePoints; i++) {
303 average += mRecentVelocities[i];
304 }
305 return average / usablePoints;
306 }
308 void startFling(boolean stopped) {
309 mDisableSnap = mSubscroller.scrolling();
311 if (stopped) {
312 mFlingState = FlingStates.STOPPED;
313 } else {
314 mVelocity = calculateFlingVelocity();
315 mFlingState = FlingStates.FLINGING;
316 }
317 }
319 /* Advances a fling animation by one step. */
320 boolean advanceFling(long realNsPerFrame) {
321 if (mFlingState != FlingStates.FLINGING) {
322 return false;
323 }
324 if (mSubscroller.scrolling() && !mSubscroller.lastScrollSucceeded()) {
325 // if the subdocument stopped scrolling, it's because it reached the end
326 // of the subdocument. we don't do overscroll on subdocuments, so there's
327 // no point in continuing this fling.
328 return false;
329 }
331 float excess = getExcess();
332 Overscroll overscroll = getOverscroll();
333 boolean decreasingOverscroll = false;
334 if ((overscroll == Overscroll.MINUS && mVelocity > 0) ||
335 (overscroll == Overscroll.PLUS && mVelocity < 0))
336 {
337 decreasingOverscroll = true;
338 }
340 if (mDisableSnap || FloatUtils.fuzzyEquals(excess, 0.0f) || decreasingOverscroll) {
341 // If we aren't overscrolled, just apply friction.
342 if (Math.abs(mVelocity) >= VELOCITY_THRESHOLD) {
343 mVelocity *= getFrameAdjustedFriction(FRICTION_FAST, realNsPerFrame);
344 } else {
345 float t = mVelocity / VELOCITY_THRESHOLD;
346 mVelocity *= FloatUtils.interpolate(getFrameAdjustedFriction(FRICTION_SLOW, realNsPerFrame),
347 getFrameAdjustedFriction(FRICTION_FAST, realNsPerFrame), t);
348 }
349 } else {
350 // Otherwise, decrease the velocity linearly.
351 float elasticity = 1.0f - excess / (getViewportLength() * SNAP_LIMIT);
352 float overscrollDecelRate = getFrameAdjustedFriction(OVERSCROLL_DECEL_RATE, realNsPerFrame);
353 if (overscroll == Overscroll.MINUS) {
354 mVelocity = Math.min((mVelocity + overscrollDecelRate) * elasticity, 0.0f);
355 } else { // must be Overscroll.PLUS
356 mVelocity = Math.max((mVelocity - overscrollDecelRate) * elasticity, 0.0f);
357 }
358 }
360 return true;
361 }
363 void stopFling() {
364 mVelocity = 0.0f;
365 mFlingState = FlingStates.STOPPED;
366 }
368 // Performs displacement of the viewport position according to the current velocity.
369 void displace() {
370 // if this isn't scrollable just return
371 if (!scrollable())
372 return;
374 if (mFlingState == FlingStates.PANNING)
375 mDisplacement += (mLastTouchPos - mTouchPos) * getEdgeResistance(false);
376 else
377 mDisplacement += mVelocity * getEdgeResistance(false);
379 // if overscroll is disabled and we're trying to overscroll, reset the displacement
380 // to remove any excess. Using getExcess alone isn't enough here since it relies on
381 // getOverscroll which doesn't take into account any new displacment being applied.
382 // If we using a subscroller, we don't want to alter the scrolling being done
383 if (getOverScrollMode() == View.OVER_SCROLL_NEVER && !mSubscroller.scrolling()) {
384 float originalDisplacement = mDisplacement;
386 if (mDisplacement + getOrigin() < getPageStart() - getMarginStart()) {
387 mDisplacement = getPageStart() - getMarginStart() - getOrigin();
388 } else if (mDisplacement + getViewportEnd() > getPageEnd() + getMarginEnd()) {
389 mDisplacement = getPageEnd() - getMarginEnd() - getViewportEnd();
390 }
392 // Return the amount of overscroll so that the overscroll controller can draw it for us
393 if (originalDisplacement != mDisplacement) {
394 if (mFlingState == FlingStates.FLINGING) {
395 overscrollFling(mVelocity / MS_PER_FRAME * 1000);
396 stopFling();
397 } else if (mFlingState == FlingStates.PANNING) {
398 overscrollPan(originalDisplacement - mDisplacement);
399 }
400 }
401 }
402 }
404 float resetDisplacement() {
405 float d = mDisplacement;
406 mDisplacement = 0.0f;
407 return d;
408 }
410 void setAutoscrollVelocity(float velocity) {
411 if (mFlingState != FlingStates.STOPPED) {
412 Log.e(LOGTAG, "Setting autoscroll velocity while in a fling is not allowed!");
413 return;
414 }
415 mVelocity = velocity;
416 }
417 }
