diff options
Diffstat (limited to 'android/source/src/java/org/mozilla/gecko/gfx/DisplayPortCalculator.java')
| -rw-r--r-- | android/source/src/java/org/mozilla/gecko/gfx/DisplayPortCalculator.java | 760 |
1 files changed, 760 insertions, 0 deletions
diff --git a/android/source/src/java/org/mozilla/gecko/gfx/DisplayPortCalculator.java b/android/source/src/java/org/mozilla/gecko/gfx/DisplayPortCalculator.java new file mode 100644 index 000000000..d98efa2d5 --- /dev/null +++ b/android/source/src/java/org/mozilla/gecko/gfx/DisplayPortCalculator.java @@ -0,0 +1,760 @@ +/* -*- 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.graphics.PointF; +import android.graphics.RectF; +import android.util.Log; + +import org.json.JSONArray; +import org.libreoffice.LOKitShell; +import org.libreoffice.LibreOfficeMainActivity; +import org.mozilla.gecko.util.FloatUtils; + +import java.util.Map; + +final class DisplayPortCalculator { + private static final String LOGTAG = DisplayPortCalculator.class.getSimpleName(); + private static final PointF ZERO_VELOCITY = new PointF(0, 0); + + // Keep this in sync with the TILEDLAYERBUFFER_TILE_SIZE defined in gfx/layers/TiledLayerBuffer.h + private static final int TILE_SIZE = 256; + + private static final String PREF_DISPLAYPORT_STRATEGY = "gfx.displayport.strategy"; + private static final String PREF_DISPLAYPORT_FM_MULTIPLIER = "gfx.displayport.strategy_fm.multiplier"; + private static final String PREF_DISPLAYPORT_FM_DANGER_X = "gfx.displayport.strategy_fm.danger_x"; + private static final String PREF_DISPLAYPORT_FM_DANGER_Y = "gfx.displayport.strategy_fm.danger_y"; + private static final String PREF_DISPLAYPORT_VB_MULTIPLIER = "gfx.displayport.strategy_vb.multiplier"; + private static final String PREF_DISPLAYPORT_VB_VELOCITY_THRESHOLD = "gfx.displayport.strategy_vb.threshold"; + private static final String PREF_DISPLAYPORT_VB_REVERSE_BUFFER = "gfx.displayport.strategy_vb.reverse_buffer"; + private static final String PREF_DISPLAYPORT_VB_DANGER_X_BASE = "gfx.displayport.strategy_vb.danger_x_base"; + private static final String PREF_DISPLAYPORT_VB_DANGER_Y_BASE = "gfx.displayport.strategy_vb.danger_y_base"; + private static final String PREF_DISPLAYPORT_VB_DANGER_X_INCR = "gfx.displayport.strategy_vb.danger_x_incr"; + private static final String PREF_DISPLAYPORT_VB_DANGER_Y_INCR = "gfx.displayport.strategy_vb.danger_y_incr"; + private static final String PREF_DISPLAYPORT_PB_VELOCITY_THRESHOLD = "gfx.displayport.strategy_pb.threshold"; + + private DisplayPortStrategy sStrategy; + private final LibreOfficeMainActivity mMainActivity; + + DisplayPortCalculator(LibreOfficeMainActivity context) { + this.mMainActivity = context; + sStrategy = new VelocityBiasStrategy(mMainActivity, null); + } + + DisplayPortMetrics calculate(ImmutableViewportMetrics metrics, PointF velocity) { + return sStrategy.calculate(metrics, (velocity == null ? ZERO_VELOCITY : velocity)); + } + + boolean aboutToCheckerboard(ImmutableViewportMetrics metrics, PointF velocity, DisplayPortMetrics displayPort) { + if (displayPort == null) { + return true; + } + return sStrategy.aboutToCheckerboard(metrics, (velocity == null ? ZERO_VELOCITY : velocity), displayPort); + } + + boolean drawTimeUpdate(long millis, int pixels) { + return sStrategy.drawTimeUpdate(millis, pixels); + } + + void resetPageState() { + sStrategy.resetPageState(); + } + + static void addPrefNames(JSONArray prefs) { + prefs.put(PREF_DISPLAYPORT_STRATEGY); + prefs.put(PREF_DISPLAYPORT_FM_MULTIPLIER); + prefs.put(PREF_DISPLAYPORT_FM_DANGER_X); + prefs.put(PREF_DISPLAYPORT_FM_DANGER_Y); + prefs.put(PREF_DISPLAYPORT_VB_MULTIPLIER); + prefs.put(PREF_DISPLAYPORT_VB_VELOCITY_THRESHOLD); + prefs.put(PREF_DISPLAYPORT_VB_REVERSE_BUFFER); + prefs.put(PREF_DISPLAYPORT_VB_DANGER_X_BASE); + prefs.put(PREF_DISPLAYPORT_VB_DANGER_Y_BASE); + prefs.put(PREF_DISPLAYPORT_VB_DANGER_X_INCR); + prefs.put(PREF_DISPLAYPORT_VB_DANGER_Y_INCR); + prefs.put(PREF_DISPLAYPORT_PB_VELOCITY_THRESHOLD); + } + + /** + * Set the active strategy to use. + * See the gfx.displayport.strategy pref in mobile/android/app/mobile.js to see the + * mapping between ints and strategies. + */ + boolean setStrategy(Map<String, Integer> prefs) { + Integer strategy = prefs.get(PREF_DISPLAYPORT_STRATEGY); + if (strategy == null) { + return false; + } + + switch (strategy) { + case 0: + sStrategy = new FixedMarginStrategy(prefs); + break; + case 1: + sStrategy = new VelocityBiasStrategy(mMainActivity, prefs); + break; + case 2: + sStrategy = new DynamicResolutionStrategy(mMainActivity, prefs); + break; + case 3: + sStrategy = new NoMarginStrategy(prefs); + break; + case 4: + sStrategy = new PredictionBiasStrategy(mMainActivity, prefs); + break; + default: + Log.e(LOGTAG, "Invalid strategy index specified"); + return false; + } + Log.i(LOGTAG, "Set strategy " + sStrategy.toString()); + return true; + } + + 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 abstract class DisplayPortStrategy { + /** Calculates a displayport given a viewport and panning velocity. */ + public abstract DisplayPortMetrics calculate(ImmutableViewportMetrics metrics, PointF velocity); + /** Returns true if a checkerboard is about to be visible and we should not throttle drawing. */ + public abstract boolean aboutToCheckerboard(ImmutableViewportMetrics metrics, PointF velocity, DisplayPortMetrics displayPort); + /** Notify the strategy of a new recorded draw time. Return false to turn off draw time recording. */ + public boolean drawTimeUpdate(long millis, int pixels) { return false; } + /** Reset any page-specific state stored, as the page being displayed has changed. */ + public void resetPageState() {} + } + + /** + * Return the dimensions for a rect that has area (width*height) that does not exceed the page size in the + * given metrics object. The area in the returned FloatSize may be less than width*height if the page is + * small, but it will never be larger than width*height. + * Note that this process may change the relative aspect ratio of the given dimensions. + */ + private static FloatSize reshapeForPage(float width, float height, ImmutableViewportMetrics metrics) { + // figure out how much of the desired buffer amount we can actually use on the horizontal axis + float usableWidth = Math.min(width, metrics.getPageWidth()); + // if we reduced the buffer amount on the horizontal axis, we should take that saved memory and + // use it on the vertical axis + float extraUsableHeight = (float)Math.floor(((width - usableWidth) * height) / usableWidth); + float usableHeight = Math.min(height + extraUsableHeight, metrics.getPageHeight()); + if (usableHeight < height && usableWidth == width) { + // and the reverse - if we shrunk the buffer on the vertical axis we can add it to the horizontal + float extraUsableWidth = (float)Math.floor(((height - usableHeight) * width) / usableHeight); + usableWidth = Math.min(width + extraUsableWidth, metrics.getPageWidth()); + } + return new FloatSize(usableWidth, usableHeight); + } + + /** + * Expand the given rect in all directions by a "danger zone". The size of the danger zone on an axis + * is the size of the view on that axis multiplied by the given multiplier. The expanded rect is then + * clamped to page bounds and returned. + */ + private static RectF expandByDangerZone(RectF rect, float dangerZoneXMultiplier, float dangerZoneYMultiplier, ImmutableViewportMetrics metrics) { + // calculate the danger zone amounts in pixels + float dangerZoneX = metrics.getWidth() * dangerZoneXMultiplier; + float dangerZoneY = metrics.getHeight() * dangerZoneYMultiplier; + rect = RectUtils.expand(rect, dangerZoneX, dangerZoneY); + // clamp to page bounds + return clampToPageBounds(rect, metrics); + } + + /** + * Expand the given margins such that when they are applied on the viewport, the resulting rect + * does not have any partial tiles, except when it is clipped by the page bounds. This assumes + * the tiles are TILE_SIZE by TILE_SIZE and start at the origin, such that there will always be + * a tile at (0,0)-(TILE_SIZE,TILE_SIZE)). + */ + private static DisplayPortMetrics getTileAlignedDisplayPortMetrics(RectF margins, float zoom, ImmutableViewportMetrics metrics) { + float left = metrics.viewportRectLeft - margins.left; + float top = metrics.viewportRectTop - margins.top; + float right = metrics.viewportRectRight + margins.right; + float bottom = metrics.viewportRectBottom + margins.bottom; + left = (float) Math.max(metrics.pageRectLeft, TILE_SIZE * Math.floor(left / TILE_SIZE)); + top = (float) Math.max(metrics.pageRectTop, TILE_SIZE * Math.floor(top / TILE_SIZE)); + right = (float) Math.min(metrics.pageRectRight, TILE_SIZE * Math.ceil(right / TILE_SIZE)); + bottom = (float) Math.min(metrics.pageRectBottom, TILE_SIZE * Math.ceil(bottom / TILE_SIZE)); + return new DisplayPortMetrics(left, top, right, bottom, zoom); + } + + /** + * Adjust the given margins so if they are applied on the viewport in the metrics, the resulting rect + * does not exceed the page bounds. This code will maintain the total margin amount for a given axis; + * it assumes that margins.left + metrics.getWidth() + margins.right is less than or equal to + * metrics.getPageWidth(); and the same for the y axis. + */ + private static RectF shiftMarginsForPageBounds(RectF margins, ImmutableViewportMetrics metrics) { + // check how much we're overflowing in each direction. note that at most one of leftOverflow + // and rightOverflow can be greater than zero, and at most one of topOverflow and bottomOverflow + // can be greater than zero, because of the assumption described in the method javadoc. + float leftOverflow = metrics.pageRectLeft - (metrics.viewportRectLeft - margins.left); + float rightOverflow = (metrics.viewportRectRight + margins.right) - metrics.pageRectRight; + float topOverflow = metrics.pageRectTop - (metrics.viewportRectTop - margins.top); + float bottomOverflow = (metrics.viewportRectBottom + margins.bottom) - metrics.pageRectBottom; + + // if the margins overflow the page bounds, shift them to other side on the same axis + if (leftOverflow > 0) { + margins.left -= leftOverflow; + margins.right += leftOverflow; + } else if (rightOverflow > 0) { + margins.right -= rightOverflow; + margins.left += rightOverflow; + } + if (topOverflow > 0) { + margins.top -= topOverflow; + margins.bottom += topOverflow; + } else if (bottomOverflow > 0) { + margins.bottom -= bottomOverflow; + margins.top += bottomOverflow; + } + return margins; + } + + /** + * Clamp the given rect to the page bounds and return it. + */ + private static RectF clampToPageBounds(RectF rect, ImmutableViewportMetrics metrics) { + if (rect.top < metrics.pageRectTop) rect.top = metrics.pageRectTop; + if (rect.left < metrics.pageRectLeft) rect.left = metrics.pageRectLeft; + if (rect.right > metrics.pageRectRight) rect.right = metrics.pageRectRight; + if (rect.bottom > metrics.pageRectBottom) rect.bottom = metrics.pageRectBottom; + return rect; + } + + /** + * This class implements the variation where we basically don't bother with a display port. + */ + private static class NoMarginStrategy extends DisplayPortStrategy { + NoMarginStrategy(Map<String, Integer> prefs) { + // no prefs in this strategy + } + + public DisplayPortMetrics calculate(ImmutableViewportMetrics metrics, PointF velocity) { + return new DisplayPortMetrics(metrics.viewportRectLeft, + metrics.viewportRectTop, + metrics.viewportRectRight, + metrics.viewportRectBottom, + metrics.zoomFactor); + } + + public boolean aboutToCheckerboard(ImmutableViewportMetrics metrics, PointF velocity, DisplayPortMetrics displayPort) { + return true; + } + + @Override + public String toString() { + return "NoMarginStrategy"; + } + } + + /** + * This class implements the variation where we use a fixed-size margin on the display port. + * The margin is always 300 pixels in all directions, except when we are (a) approaching a page + * boundary, and/or (b) if we are limited by the page size. In these cases we try to maintain + * the area of the display port by (a) shifting the buffer to the other side on the same axis, + * and/or (b) increasing the buffer on the other axis to compensate for the reduced buffer on + * one axis. + */ + private static class FixedMarginStrategy extends DisplayPortStrategy { + // The length of each axis of the display port will be the corresponding view length + // multiplied by this factor. + private final float SIZE_MULTIPLIER; + + // If the visible rect is within the danger zone (measured as a fraction of the view size + // from the edge of the displayport) we start redrawing to minimize checkerboarding. + private final float DANGER_ZONE_X_MULTIPLIER; + private final float DANGER_ZONE_Y_MULTIPLIER; + + FixedMarginStrategy(Map<String, Integer> prefs) { + SIZE_MULTIPLIER = getFloatPref(prefs, PREF_DISPLAYPORT_FM_MULTIPLIER, 2000); + DANGER_ZONE_X_MULTIPLIER = getFloatPref(prefs, PREF_DISPLAYPORT_FM_DANGER_X, 100); + DANGER_ZONE_Y_MULTIPLIER = getFloatPref(prefs, PREF_DISPLAYPORT_FM_DANGER_Y, 200); + } + + public DisplayPortMetrics calculate(ImmutableViewportMetrics metrics, PointF velocity) { + float displayPortWidth = metrics.getWidth() * SIZE_MULTIPLIER; + float displayPortHeight = metrics.getHeight() * SIZE_MULTIPLIER; + + // we need to avoid having a display port that is larger than the page, or we will end up + // painting things outside the page bounds (bug 729169). we simultaneously need to make + // the display port as large as possible so that we redraw less. reshape the display + // port dimensions to accomplish this. + FloatSize usableSize = reshapeForPage(displayPortWidth, displayPortHeight, metrics); + float horizontalBuffer = usableSize.width - metrics.getWidth(); + float verticalBuffer = usableSize.height - metrics.getHeight(); + + // and now calculate the display port margins based on how much buffer we've decided to use and + // the page bounds, ensuring we use all of the available buffer amounts on one side or the other + // on any given axis. (i.e. if we're scrolled to the top of the page, the vertical buffer is + // entirely below the visible viewport, but if we're halfway down the page, the vertical buffer + // is split). + RectF margins = new RectF(); + margins.left = horizontalBuffer / 2.0f; + margins.right = horizontalBuffer - margins.left; + margins.top = verticalBuffer / 2.0f; + margins.bottom = verticalBuffer - margins.top; + margins = shiftMarginsForPageBounds(margins, metrics); + + return getTileAlignedDisplayPortMetrics(margins, metrics.zoomFactor, metrics); + } + + public boolean aboutToCheckerboard(ImmutableViewportMetrics metrics, PointF velocity, DisplayPortMetrics displayPort) { + // Increase the size of the viewport based on the danger zone multiplier (and clamp to page + // boundaries), and intersect it with the current displayport to determine whether we're + // close to checkerboarding. + RectF adjustedViewport = expandByDangerZone(metrics.getViewport(), DANGER_ZONE_X_MULTIPLIER, DANGER_ZONE_Y_MULTIPLIER, metrics); + return !displayPort.contains(adjustedViewport); + } + + @Override + public String toString() { + return "FixedMarginStrategy mult=" + SIZE_MULTIPLIER + ", dangerX=" + DANGER_ZONE_X_MULTIPLIER + ", dangerY=" + DANGER_ZONE_Y_MULTIPLIER; + } + } + + /** + * This class implements the variation with a small fixed-size margin with velocity bias. + * In this variation, the default margins are pretty small relative to the view size, but + * they are affected by the panning velocity. Specifically, if we are panning on one axis, + * we remove the margins on the other axis because we are likely axis-locked. Also once + * we are panning in one direction above a certain threshold velocity, we shift the buffer + * so that it is almost entirely in the direction of the pan, with a little bit in the + * reverse direction. + */ + private static class VelocityBiasStrategy extends DisplayPortStrategy { + // The length of each axis of the display port will be the corresponding view length + // multiplied by this factor. + private final float SIZE_MULTIPLIER; + // The velocity above which we apply the velocity bias + private final float VELOCITY_THRESHOLD; + // How much of the buffer to keep in the reverse direction of the velocity + private final float REVERSE_BUFFER; + // If the visible rect is within the danger zone we start redrawing to minimize + // checkerboarding. the danger zone amount is a linear function of the form: + // viewportsize * (base + velocity * incr) + // where base and incr are configurable values. + private final float DANGER_ZONE_BASE_X_MULTIPLIER; + private final float DANGER_ZONE_BASE_Y_MULTIPLIER; + private final float DANGER_ZONE_INCR_X_MULTIPLIER; + private final float DANGER_ZONE_INCR_Y_MULTIPLIER; + + VelocityBiasStrategy(LibreOfficeMainActivity context, Map<String, Integer> prefs) { + SIZE_MULTIPLIER = getFloatPref(prefs, PREF_DISPLAYPORT_VB_MULTIPLIER, 2000); + VELOCITY_THRESHOLD = LOKitShell.getDpi(context) * getFloatPref(prefs, PREF_DISPLAYPORT_VB_VELOCITY_THRESHOLD, 32); + REVERSE_BUFFER = getFloatPref(prefs, PREF_DISPLAYPORT_VB_REVERSE_BUFFER, 200); + DANGER_ZONE_BASE_X_MULTIPLIER = getFloatPref(prefs, PREF_DISPLAYPORT_VB_DANGER_X_BASE, 1000); + DANGER_ZONE_BASE_Y_MULTIPLIER = getFloatPref(prefs, PREF_DISPLAYPORT_VB_DANGER_Y_BASE, 1000); + DANGER_ZONE_INCR_X_MULTIPLIER = getFloatPref(prefs, PREF_DISPLAYPORT_VB_DANGER_X_INCR, 0); + DANGER_ZONE_INCR_Y_MULTIPLIER = getFloatPref(prefs, PREF_DISPLAYPORT_VB_DANGER_Y_INCR, 0); + } + + /** + * Split the given amounts into margins based on the VELOCITY_THRESHOLD and REVERSE_BUFFER values. + * If the velocity is above the VELOCITY_THRESHOLD on an axis, split the amount into REVERSE_BUFFER + * and 1.0 - REVERSE_BUFFER fractions. The REVERSE_BUFFER fraction is set as the margin in the + * direction opposite to the velocity, and the remaining fraction is set as the margin in the direction + * of the velocity. If the velocity is lower than VELOCITY_THRESHOLD, split the amount evenly into the + * two margins on that axis. + */ + private RectF velocityBiasedMargins(float xAmount, float yAmount, PointF velocity) { + RectF margins = new RectF(); + + if (velocity.x > VELOCITY_THRESHOLD) { + margins.left = xAmount * REVERSE_BUFFER; + } else if (velocity.x < -VELOCITY_THRESHOLD) { + margins.left = xAmount * (1.0f - REVERSE_BUFFER); + } else { + margins.left = xAmount / 2.0f; + } + margins.right = xAmount - margins.left; + + if (velocity.y > VELOCITY_THRESHOLD) { + margins.top = yAmount * REVERSE_BUFFER; + } else if (velocity.y < -VELOCITY_THRESHOLD) { + margins.top = yAmount * (1.0f - REVERSE_BUFFER); + } else { + margins.top = yAmount / 2.0f; + } + margins.bottom = yAmount - margins.top; + + return margins; + } + + public DisplayPortMetrics calculate(ImmutableViewportMetrics metrics, PointF velocity) { + float displayPortWidth = metrics.getWidth() * SIZE_MULTIPLIER; + float displayPortHeight = metrics.getHeight() * SIZE_MULTIPLIER; + + // but if we're panning on one axis, set the margins for the other axis to zero since we are likely + // axis locked and won't be displaying that extra area. + if (Math.abs(velocity.x) > VELOCITY_THRESHOLD && FloatUtils.fuzzyEquals(velocity.y, 0)) { + displayPortHeight = metrics.getHeight(); + } else if (Math.abs(velocity.y) > VELOCITY_THRESHOLD && FloatUtils.fuzzyEquals(velocity.x, 0)) { + displayPortWidth = metrics.getWidth(); + } + + // we need to avoid having a display port that is larger than the page, or we will end up + // painting things outside the page bounds (bug 729169). + displayPortWidth = Math.min(displayPortWidth, metrics.getPageWidth()); + displayPortHeight = Math.min(displayPortHeight, metrics.getPageHeight()); + float horizontalBuffer = displayPortWidth - metrics.getWidth(); + float verticalBuffer = displayPortHeight - metrics.getHeight(); + + // split the buffer amounts into margins based on velocity, and shift it to + // take into account the page bounds + RectF margins = velocityBiasedMargins(horizontalBuffer, verticalBuffer, velocity); + margins = shiftMarginsForPageBounds(margins, metrics); + + return getTileAlignedDisplayPortMetrics(margins, metrics.zoomFactor, metrics); + } + + public boolean aboutToCheckerboard(ImmutableViewportMetrics metrics, PointF velocity, DisplayPortMetrics displayPort) { + // calculate the danger zone amounts based on the prefs + float dangerZoneX = metrics.getWidth() * (DANGER_ZONE_BASE_X_MULTIPLIER + (velocity.x * DANGER_ZONE_INCR_X_MULTIPLIER)); + float dangerZoneY = metrics.getHeight() * (DANGER_ZONE_BASE_Y_MULTIPLIER + (velocity.y * DANGER_ZONE_INCR_Y_MULTIPLIER)); + // clamp it such that when added to the viewport, they don't exceed page size. + // this is a prerequisite to calling shiftMarginsForPageBounds as we do below. + dangerZoneX = Math.min(dangerZoneX, metrics.getPageWidth() - metrics.getWidth()); + dangerZoneY = Math.min(dangerZoneY, metrics.getPageHeight() - metrics.getHeight()); + + // split the danger zone into margins based on velocity, and ensure it doesn't exceed + // page bounds. + RectF dangerMargins = velocityBiasedMargins(dangerZoneX, dangerZoneY, velocity); + dangerMargins = shiftMarginsForPageBounds(dangerMargins, metrics); + + // we're about to checkerboard if the current viewport area + the danger zone margins + // fall out of the current displayport anywhere. + RectF adjustedViewport = new RectF( + metrics.viewportRectLeft - dangerMargins.left, + metrics.viewportRectTop - dangerMargins.top, + metrics.viewportRectRight + dangerMargins.right, + metrics.viewportRectBottom + dangerMargins.bottom); + return !displayPort.contains(adjustedViewport); + } + + @Override + public String toString() { + return "VelocityBiasStrategy mult=" + SIZE_MULTIPLIER + ", threshold=" + VELOCITY_THRESHOLD + ", reverse=" + REVERSE_BUFFER + + ", dangerBaseX=" + DANGER_ZONE_BASE_X_MULTIPLIER + ", dangerBaseY=" + DANGER_ZONE_BASE_Y_MULTIPLIER + + ", dangerIncrX=" + DANGER_ZONE_INCR_Y_MULTIPLIER + ", dangerIncrY=" + DANGER_ZONE_INCR_Y_MULTIPLIER; + } + } + + /** + * This class implements the variation where we draw more of the page at low resolution while panning. + * In this variation, as we pan faster, we increase the page area we are drawing, but reduce the draw + * resolution to compensate. This results in the same device-pixel area drawn; the compositor then + * scales this up to the viewport zoom level. This results in a large area of the page drawn but it + * looks blurry. The assumption is that drawing extra that we never display is better than checkerboarding, + * where we draw less but never even show it on the screen. + */ + private static class DynamicResolutionStrategy extends DisplayPortStrategy { + + // The velocity above which we start zooming out the display port to keep up + // with the panning. + private final float VELOCITY_EXPANSION_THRESHOLD; + + + DynamicResolutionStrategy(LibreOfficeMainActivity context, Map<String, Integer> prefs) { + // ignore prefs for now + VELOCITY_EXPANSION_THRESHOLD = LOKitShell.getDpi(context) / 16f; + VELOCITY_FAST_THRESHOLD = VELOCITY_EXPANSION_THRESHOLD * 2.0f; + } + + // The length of each axis of the display port will be the corresponding view length + // multiplied by this factor. + private static final float SIZE_MULTIPLIER = 1.5f; + + // How much we increase the display port based on velocity. Assuming no friction and + // splitting (see below), this should be the number of frames (@60fps) between us + // calculating the display port and the draw of the *next* display port getting composited + // and displayed on the screen. This is because the timeline looks like this: + // Java: pan pan pan pan pan pan ! pan pan pan pan pan pan ! + // Gecko: \-> draw -> composite / \-> draw -> composite / + // The display port calculated on the first "pan" gets composited to the screen at the + // first exclamation mark, and remains on the screen until the second exclamation mark. + // In order to avoid checkerboarding, that display port must be able to contain all of + // the panning until the second exclamation mark, which encompasses two entire draw/composite + // cycles. + // If we take into account friction, our velocity multiplier should be reduced as the + // amount of pan will decrease each time. If we take into account display port splitting, + // it should be increased as the splitting means some of the display port will be used to + // draw in the opposite direction of the velocity. For now I'm assuming these two cancel + // each other out. + private static final float VELOCITY_MULTIPLIER = 60.0f; + + // The following constants adjust how biased the display port is in the direction of panning. + // When panning fast (above the FAST_THRESHOLD) we use the fast split factor to split the + // display port "buffer" area, otherwise we use the slow split factor. This is based on the + // assumption that if the user is panning fast, they are less likely to reverse directions + // and go backwards, so we should spend more of our display port buffer in the direction of + // panning. + private final float VELOCITY_FAST_THRESHOLD; + private static final float FAST_SPLIT_FACTOR = 0.95f; + private static final float SLOW_SPLIT_FACTOR = 0.8f; + + // The following constants are used for viewport prediction; we use them to estimate where + // the viewport will be soon and whether or not we should trigger a draw right now. "soon" + // in the previous sentence really refers to the amount of time it would take to draw and + // composite from the point at which we do the calculation, and that is not really a known + // quantity. The velocity multiplier is how much we multiply the velocity by; it has the + // same caveats as the VELOCITY_MULTIPLIER above except that it only needs to take into account + // one draw/composite cycle instead of two. The danger zone multiplier is a multiplier of the + // viewport size that we use as an extra "danger zone" around the viewport; if this danger + // zone falls outside the display port then we are approaching the point at which we will + // checkerboard, and hence should start drawing. Note that if DANGER_ZONE_MULTIPLIER is + // greater than (SIZE_MULTIPLIER - 1.0f), then at zero velocity we will always be in the + // danger zone, and thus will be constantly drawing. + private static final float PREDICTION_VELOCITY_MULTIPLIER = 30.0f; + private static final float DANGER_ZONE_MULTIPLIER = 0.20f; // must be less than (SIZE_MULTIPLIER - 1.0f) + + public DisplayPortMetrics calculate(ImmutableViewportMetrics metrics, PointF velocity) { + float displayPortWidth = metrics.getWidth() * SIZE_MULTIPLIER; + float displayPortHeight = metrics.getHeight() * SIZE_MULTIPLIER; + + // for resolution calculation purposes, we need to know what the adjusted display port dimensions + // would be if we had zero velocity, so calculate that here before we increase the display port + // based on velocity. + FloatSize reshapedSize = reshapeForPage(displayPortWidth, displayPortHeight, metrics); + + // increase displayPortWidth and displayPortHeight based on the velocity, but maintaining their + // relative aspect ratio. + if (velocity.length() > VELOCITY_EXPANSION_THRESHOLD) { + float velocityFactor = Math.max(Math.abs(velocity.x) / displayPortWidth, + Math.abs(velocity.y) / displayPortHeight); + velocityFactor *= VELOCITY_MULTIPLIER; + + displayPortWidth += (displayPortWidth * velocityFactor); + displayPortHeight += (displayPortHeight * velocityFactor); + } + + // at this point, displayPortWidth and displayPortHeight are how much of the page (in device pixels) + // we want to be rendered by Gecko. Note here "device pixels" is equivalent to CSS pixels multiplied + // by metrics.zoomFactor + + // we need to avoid having a display port that is larger than the page, or we will end up + // painting things outside the page bounds (bug 729169). we simultaneously need to make + // the display port as large as possible so that we redraw less. reshape the display + // port dimensions to accomplish this. this may change the aspect ratio of the display port, + // but we are assuming that this is desirable because the advantages from pre-drawing will + // outweigh the disadvantages from any buffer reallocations that might occur. + FloatSize usableSize = reshapeForPage(displayPortWidth, displayPortHeight, metrics); + float horizontalBuffer = usableSize.width - metrics.getWidth(); + float verticalBuffer = usableSize.height - metrics.getHeight(); + + // at this point, horizontalBuffer and verticalBuffer are the dimensions of the buffer area we have. + // the buffer area is the off-screen area that is part of the display port and will be pre-drawn in case + // the user scrolls there. we now need to split the buffer area on each axis so that we know + // what the exact margins on each side will be. first we split the buffer amount based on the direction + // we're moving, so that we have a larger buffer in the direction of travel. + RectF margins = new RectF(); + margins.left = splitBufferByVelocity(horizontalBuffer, velocity.x); + margins.right = horizontalBuffer - margins.left; + margins.top = splitBufferByVelocity(verticalBuffer, velocity.y); + margins.bottom = verticalBuffer - margins.top; + + // then, we account for running into the page bounds - so that if we hit the top of the page, we need + // to drop the top margin and move that amount to the bottom margin. + margins = shiftMarginsForPageBounds(margins, metrics); + + // finally, we calculate the resolution we want to render the display port area at. We do this + // so that as we expand the display port area (because of velocity), we reduce the resolution of + // the painted area so as to maintain the size of the buffer Gecko is painting into. we calculate + // the reduction in resolution by comparing the display port size with and without the velocity + // changes applied. + // this effectively means that as we pan faster and faster, the display port grows, but we paint + // at lower resolutions. this paints more area to reduce checkerboard at the cost of increasing + // compositor-scaling and blurriness. Once we stop panning, the blurriness must be entirely gone. + // Note that usable* could be less than base* if we are pinch-zoomed out into overscroll, so we + // clamp it to make sure this doesn't increase our display resolution past metrics.zoomFactor. + float scaleFactor = Math.min(reshapedSize.width / usableSize.width, reshapedSize.height / usableSize.height); + float displayResolution = metrics.zoomFactor * Math.min(1.0f, scaleFactor); + + return new DisplayPortMetrics( + metrics.viewportRectLeft - margins.left, + metrics.viewportRectTop - margins.top, + metrics.viewportRectRight + margins.right, + metrics.viewportRectBottom + margins.bottom, + displayResolution); + } + + /** + * Split the given buffer amount into two based on the velocity. + * Given an amount of total usable buffer on an axis, this will + * return the amount that should be used on the left/top side of + * the axis (the side which a negative velocity vector corresponds + * to). + */ + private float splitBufferByVelocity(float amount, float velocity) { + // if no velocity, so split evenly + if (FloatUtils.fuzzyEquals(velocity, 0)) { + return amount / 2.0f; + } + // if we're moving quickly, assign more of the amount in that direction + // since is less likely that we will reverse direction immediately + if (velocity < -VELOCITY_FAST_THRESHOLD) { + return amount * FAST_SPLIT_FACTOR; + } + if (velocity > VELOCITY_FAST_THRESHOLD) { + return amount * (1.0f - FAST_SPLIT_FACTOR); + } + // if we're moving slowly, then assign less of the amount in that direction + if (velocity < 0) { + return amount * SLOW_SPLIT_FACTOR; + } else { + return amount * (1.0f - SLOW_SPLIT_FACTOR); + } + } + + public boolean aboutToCheckerboard(ImmutableViewportMetrics metrics, PointF velocity, DisplayPortMetrics displayPort) { + // Expand the viewport based on our velocity (and clamp it to page boundaries). + // Then intersect it with the last-requested displayport to determine whether we're + // close to checkerboarding. + + RectF predictedViewport = metrics.getViewport(); + + // first we expand the viewport in the direction we're moving based on some + // multiple of the current velocity. + if (velocity.length() > 0) { + if (velocity.x < 0) { + predictedViewport.left += velocity.x * PREDICTION_VELOCITY_MULTIPLIER; + } else if (velocity.x > 0) { + predictedViewport.right += velocity.x * PREDICTION_VELOCITY_MULTIPLIER; + } + + if (velocity.y < 0) { + predictedViewport.top += velocity.y * PREDICTION_VELOCITY_MULTIPLIER; + } else if (velocity.y > 0) { + predictedViewport.bottom += velocity.y * PREDICTION_VELOCITY_MULTIPLIER; + } + } + + // then we expand the viewport evenly in all directions just to have an extra + // safety zone. this also clamps it to page bounds. + predictedViewport = expandByDangerZone(predictedViewport, DANGER_ZONE_MULTIPLIER, DANGER_ZONE_MULTIPLIER, metrics); + return !displayPort.contains(predictedViewport); + } + + @Override + public String toString() { + return "DynamicResolutionStrategy"; + } + } + + /** + * This class implements the variation where we use the draw time to predict where we will be when + * a draw completes, and draw that instead of where we are now. In this variation, when our panning + * speed drops below a certain threshold, we draw 9 viewports' worth of content so that the user can + * pan in any direction without encountering checkerboarding. + * Once the user is panning, we modify the displayport to encompass an area range of where we think + * the user will be when the draw completes. This heuristic relies on both the estimated draw time + * the panning velocity; unexpected changes in either of these values will cause the heuristic to + * fail and show checkerboard. + */ + private static class PredictionBiasStrategy extends DisplayPortStrategy { + private static float VELOCITY_THRESHOLD; + + private int mPixelArea; // area of the viewport, used in draw time calculations + private int mMinFramesToDraw; // minimum number of frames we take to draw + private int mMaxFramesToDraw; // maximum number of frames we take to draw + + PredictionBiasStrategy(LibreOfficeMainActivity context, Map<String, Integer> prefs) { + VELOCITY_THRESHOLD = LOKitShell.getDpi(context) * getFloatPref(prefs, PREF_DISPLAYPORT_PB_VELOCITY_THRESHOLD, 16); + resetPageState(); + } + + public DisplayPortMetrics calculate(ImmutableViewportMetrics metrics, PointF velocity) { + float width = metrics.getWidth(); + float height = metrics.getHeight(); + mPixelArea = (int)(width * height); + + if (velocity.length() < VELOCITY_THRESHOLD) { + // if we're going slow, expand the displayport to 9x viewport size + RectF margins = new RectF(width, height, width, height); + return getTileAlignedDisplayPortMetrics(margins, metrics.zoomFactor, metrics); + } + + // figure out how far we expect to be + float minDx = velocity.x * mMinFramesToDraw; + float minDy = velocity.y * mMinFramesToDraw; + float maxDx = velocity.x * mMaxFramesToDraw; + float maxDy = velocity.y * mMaxFramesToDraw; + + // figure out how many pixels we will be drawing when we draw the above-calculated range. + // this will be larger than the viewport area. + float pixelsToDraw = (width + Math.abs(maxDx - minDx)) * (height + Math.abs(maxDy - minDy)); + // adjust how far we will get because of the time spent drawing all these extra pixels. this + // will again increase the number of pixels drawn so really we could keep iterating this over + // and over, but once seems enough for now. + maxDx = maxDx * pixelsToDraw / mPixelArea; + maxDy = maxDy * pixelsToDraw / mPixelArea; + + // and finally generate the displayport. the min/max stuff takes care of + // negative velocities as well as positive. + RectF margins = new RectF( + -Math.min(minDx, maxDx), + -Math.min(minDy, maxDy), + Math.max(minDx, maxDx), + Math.max(minDy, maxDy)); + return getTileAlignedDisplayPortMetrics(margins, metrics.zoomFactor, metrics); + } + + public boolean aboutToCheckerboard(ImmutableViewportMetrics metrics, PointF velocity, DisplayPortMetrics displayPort) { + // the code below is the same as in calculate() but is awkward to refactor since it has multiple outputs. + // refer to the comments in calculate() to understand what this is doing. + float minDx = velocity.x * mMinFramesToDraw; + float minDy = velocity.y * mMinFramesToDraw; + float maxDx = velocity.x * mMaxFramesToDraw; + float maxDy = velocity.y * mMaxFramesToDraw; + float pixelsToDraw = (metrics.getWidth() + Math.abs(maxDx - minDx)) * (metrics.getHeight() + Math.abs(maxDy - minDy)); + maxDx = maxDx * pixelsToDraw / mPixelArea; + maxDy = maxDy * pixelsToDraw / mPixelArea; + + // now that we have an idea of how far we will be when the draw completes, take the farthest + // end of that range and see if it falls outside the displayport bounds. if it does, allow + // the draw to go through + RectF predictedViewport = metrics.getViewport(); + predictedViewport.left += maxDx; + predictedViewport.top += maxDy; + predictedViewport.right += maxDx; + predictedViewport.bottom += maxDy; + + predictedViewport = clampToPageBounds(predictedViewport, metrics); + return !displayPort.contains(predictedViewport); + } + + @Override + public boolean drawTimeUpdate(long millis, int pixels) { + // calculate the number of frames it took to draw a viewport-sized area + float normalizedTime = (float)mPixelArea * (float)millis / (float)pixels; + int normalizedFrames = (int)Math.ceil(normalizedTime * 60f / 1000f); + // broaden our range on how long it takes to draw if the draw falls outside + // the range. this allows it to grow gradually. this heuristic may need to + // be tweaked into more of a floating window average or something. + if (normalizedFrames <= mMinFramesToDraw) { + mMinFramesToDraw--; + } else if (normalizedFrames > mMaxFramesToDraw) { + mMaxFramesToDraw++; + } else { + return true; + } + Log.d(LOGTAG, "Widened draw range to [" + mMinFramesToDraw + ", " + mMaxFramesToDraw + "]"); + return true; + } + + @Override + public void resetPageState() { + mMinFramesToDraw = 0; + mMaxFramesToDraw = 2; + } + + @Override + public String toString() { + return "PredictionBiasStrategy threshold=" + VELOCITY_THRESHOLD; + } + } +} |