DXR is a code search and navigation tool aimed at making sense of large projects. It supports full-text and regex searches as well as structural queries.

Header

Mercurial (31ec81b5d7bb)

VCS Links

Line Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349
/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * 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/. */

#include "LayerSorter.h"
#include <math.h>                       // for fabs
#include <stdint.h>                     // for uint32_t
#include <stdio.h>                      // for fprintf, stderr, FILE
#include <stdlib.h>                     // for getenv
#include "DirectedGraph.h"              // for DirectedGraph
#include "Layers.h"                     // for Layer
#include "gfx3DMatrix.h"                // for gfx3DMatrix
#include "gfxLineSegment.h"             // for gfxLineSegment
#include "gfxPoint.h"                   // for gfxPoint
#include "gfxPoint3D.h"                 // for gfxPoint3D
#include "gfxQuad.h"                    // for gfxQuad
#include "gfxRect.h"                    // for gfxRect
#include "gfxTypes.h"                   // for gfxFloat
#include "mozilla/gfx/BasePoint3D.h"    // for BasePoint3D
#include "nsRegion.h"                   // for nsIntRegion
#include "nsTArray.h"                   // for nsTArray, etc
#include "limits.h"
#include "mozilla/Assertions.h"

namespace mozilla {
namespace layers {

enum LayerSortOrder {
  Undefined,
  ABeforeB,
  BBeforeA,
};

/**
 * Recover the z component from a 2d transformed point by finding the intersection
 * of a line through the point in the z direction and the transformed plane.
 *
 * We want to solve:
 *
 * point = normal . (p0 - l0) / normal . l
 */
static gfxFloat RecoverZDepth(const gfx3DMatrix& aTransform, const gfxPoint& aPoint)
{
    const gfxPoint3D l(0, 0, 1);
    gfxPoint3D l0 = gfxPoint3D(aPoint.x, aPoint.y, 0);
    gfxPoint3D p0 = aTransform.Transform3D(gfxPoint3D(0, 0, 0));
    gfxPoint3D normal = aTransform.GetNormalVector();

    gfxFloat n = normal.DotProduct(p0 - l0); 
    gfxFloat d = normal.DotProduct(l);

    if (!d) {
        return 0;
    }

    return n/d;
}

/**
 * Determine if this transform layer should be drawn before another when they 
 * are both preserve-3d children.
 *
 * We want to find the relative z depths of the 2 layers at points where they
 * intersect when projected onto the 2d screen plane. Intersections are defined
 * as corners that are positioned within the other quad, as well as intersections
 * of the lines.
 *
 * We then choose the intersection point with the greatest difference in Z
 * depths and use this point to determine an ordering for the two layers.
 * For layers that are intersecting in 3d space, this essentially guesses an 
 * order. In a lot of cases we only intersect right at the edge point (3d cubes
 * in particular) and this generates the 'correct' looking ordering. For planes
 * that truely intersect, then there is no correct ordering and this remains
 * unsolved without changing our rendering code.
 */
static LayerSortOrder CompareDepth(Layer* aOne, Layer* aTwo) {
  gfxRect ourRect = aOne->GetEffectiveVisibleRegion().GetBounds();
  gfxRect otherRect = aTwo->GetEffectiveVisibleRegion().GetBounds();

  gfx3DMatrix ourTransform = aOne->GetTransform();
  gfx3DMatrix otherTransform = aTwo->GetTransform();

  // Transform both rectangles and project into 2d space.
  gfxQuad ourTransformedRect = ourTransform.TransformRect(ourRect);
  gfxQuad otherTransformedRect = otherTransform.TransformRect(otherRect);

  gfxRect ourBounds = ourTransformedRect.GetBounds();
  gfxRect otherBounds = otherTransformedRect.GetBounds();

  if (!ourBounds.Intersects(otherBounds)) {
    return Undefined;
  }

  // Make a list of all points that are within the other rect.
  // Could we just check Contains() on the bounds rects. ie, is it possible
  // for layers to overlap without intersections (in 2d space) and yet still
  // have their bounds rects not completely enclose each other?
  nsTArray<gfxPoint> points;
  for (uint32_t i = 0; i < 4; i++) {
    if (ourTransformedRect.Contains(otherTransformedRect.mPoints[i])) {
      points.AppendElement(otherTransformedRect.mPoints[i]);
    }
    if (otherTransformedRect.Contains(ourTransformedRect.mPoints[i])) {
      points.AppendElement(ourTransformedRect.mPoints[i]);
    }
  }
  
  // Look for intersections between lines (in 2d space) and use these as
  // depth testing points.
  for (uint32_t i = 0; i < 4; i++) {
    for (uint32_t j = 0; j < 4; j++) {
      gfxPoint intersection;
      gfxLineSegment one(ourTransformedRect.mPoints[i],
                         ourTransformedRect.mPoints[(i + 1) % 4]);
      gfxLineSegment two(otherTransformedRect.mPoints[j],
                         otherTransformedRect.mPoints[(j + 1) % 4]);
      if (one.Intersects(two, intersection)) {
        points.AppendElement(intersection);
      }
    }
  }

  // No intersections, no defined order between these layers.
  if (points.IsEmpty()) {
    return Undefined;
  }

  // Find the relative Z depths of each intersection point and check that the layers are in the same order.
  gfxFloat highest = 0;
  for (uint32_t i = 0; i < points.Length(); i++) {
    gfxFloat ourDepth = RecoverZDepth(ourTransform, points.ElementAt(i));
    gfxFloat otherDepth = RecoverZDepth(otherTransform, points.ElementAt(i));

    gfxFloat difference = otherDepth - ourDepth;

    if (fabs(difference) > fabs(highest)) {
      highest = difference;
    }
  }
  // If layers have the same depth keep the original order
  if (fabs(highest) < 0.1 || highest >= 0) {
    return ABeforeB;
  } else {
    return BBeforeA;
  }
}

#ifdef DEBUG
static bool gDumpLayerSortList = getenv("MOZ_DUMP_LAYER_SORT_LIST") != 0;

#define BLACK       0
#define RED         1
#define GREEN       2
#define YELLOW      3
#define BLUE        4
#define MAGENTA     5
#define CYAN        6
#define WHITE       7

//#define USE_XTERM_COLORING
#ifdef USE_XTERM_COLORING

#define RESET       0
#define BRIGHT      1
#define DIM         2
#define UNDERLINE   3
#define BLINK       4
#define REVERSE     7
#define HIDDEN      8

static void SetTextColor(uint32_t aColor)
{
  char command[13];

  /* Command is the control command to the terminal */
  sprintf(command, "%c[%d;%d;%dm", 0x1B, RESET, aColor + 30, BLACK + 40);
  printf("%s", command);
}

static void print_layer_internal(FILE* aFile, Layer* aLayer, uint32_t aColor)
{
  SetTextColor(aColor);
  fprintf(aFile, "%p", aLayer);
  SetTextColor(GREEN);
}
#else

const char *colors[] = { "Black", "Red", "Green", "Yellow", "Blue", "Magenta", "Cyan", "White" };

static void print_layer_internal(FILE* aFile, Layer* aLayer, uint32_t aColor)
{
  fprintf(aFile, "%p(%s)", aLayer, colors[aColor]);
}
#endif

static void print_layer(FILE* aFile, Layer* aLayer)
{
  print_layer_internal(aFile, aLayer, aLayer->GetDebugColorIndex());
}

static void DumpLayerList(nsTArray<Layer*>& aLayers)
{
  for (uint32_t i = 0; i < aLayers.Length(); i++) {
    print_layer(stderr, aLayers.ElementAt(i));
    fprintf(stderr, " ");
  }
  fprintf(stderr, "\n");
}

static void DumpEdgeList(DirectedGraph<Layer*>& aGraph)
{
  const nsTArray<DirectedGraph<Layer*>::Edge>& edges = aGraph.GetEdgeList();
  
  for (uint32_t i = 0; i < edges.Length(); i++) {
    fprintf(stderr, "From: ");
    print_layer(stderr, edges.ElementAt(i).mFrom);
    fprintf(stderr, ", To: ");
    print_layer(stderr, edges.ElementAt(i).mTo);
    fprintf(stderr, "\n");
  }
}
#endif

// The maximum number of layers that we will attempt to sort. Anything
// greater than this will be left unsorted. We should consider enabling
// depth buffering for the scene in this case.
#define MAX_SORTABLE_LAYERS 100


uint32_t gColorIndex = 1;

void SortLayersBy3DZOrder(nsTArray<Layer*>& aLayers)
{
  uint32_t nodeCount = aLayers.Length();
  if (nodeCount > MAX_SORTABLE_LAYERS) {
    return;
  }
  DirectedGraph<Layer*> graph;

#ifdef DEBUG
  if (gDumpLayerSortList) {
    for (uint32_t i = 0; i < nodeCount; i++) {
      if (aLayers.ElementAt(i)->GetDebugColorIndex() == 0) {
        aLayers.ElementAt(i)->SetDebugColorIndex(gColorIndex++);
        if (gColorIndex > 7) {
          gColorIndex = 1;
        }
      }
    }
    fprintf(stderr, " --- Layers before sorting: --- \n");
    DumpLayerList(aLayers);
  }
#endif

  // Iterate layers and determine edges.
  for (uint32_t i = 0; i < nodeCount; i++) {
    for (uint32_t j = i + 1; j < nodeCount; j++) {
      Layer* a = aLayers.ElementAt(i);
      Layer* b = aLayers.ElementAt(j);
      LayerSortOrder order = CompareDepth(a, b);
      if (order == ABeforeB) {
        graph.AddEdge(a, b);
      } else if (order == BBeforeA) {
        graph.AddEdge(b, a);
      }
    }
  }

#ifdef DEBUG
  if (gDumpLayerSortList) {
    fprintf(stderr, " --- Edge List: --- \n");
    DumpEdgeList(graph);
  }
#endif

  // Build a new array using the graph.
  nsTArray<Layer*> noIncoming;
  nsTArray<Layer*> sortedList;

  // Make a list of all layers with no incoming edges.
  noIncoming.AppendElements(aLayers);
  const nsTArray<DirectedGraph<Layer*>::Edge>& edges = graph.GetEdgeList();
  for (uint32_t i = 0; i < edges.Length(); i++) {
    noIncoming.RemoveElement(edges.ElementAt(i).mTo);
  }

  // Move each item without incoming edges into the sorted list,
  // and remove edges from it.
  do {
    if (!noIncoming.IsEmpty()) {
      uint32_t last = noIncoming.Length() - 1;

      Layer* layer = noIncoming.ElementAt(last);
      MOZ_ASSERT(layer); // don't let null layer pointers sneak into sortedList

      noIncoming.RemoveElementAt(last);
      sortedList.AppendElement(layer);

      nsTArray<DirectedGraph<Layer*>::Edge> outgoing;
      graph.GetEdgesFrom(layer, outgoing);
      for (uint32_t i = 0; i < outgoing.Length(); i++) {
        DirectedGraph<Layer*>::Edge edge = outgoing.ElementAt(i);
        graph.RemoveEdge(edge);
        if (!graph.NumEdgesTo(edge.mTo)) {
          // If this node also has no edges now, add it to the list
          noIncoming.AppendElement(edge.mTo);
        }
      }
    }

    // If there are no nodes without incoming edges, but there
    // are still edges, then we have a cycle.
    if (noIncoming.IsEmpty() && graph.GetEdgeCount()) {
      // Find the node with the least incoming edges.
      uint32_t minEdges = UINT_MAX;
      Layer* minNode = nullptr;
      for (uint32_t i = 0; i < aLayers.Length(); i++) {
        uint32_t edgeCount = graph.NumEdgesTo(aLayers.ElementAt(i));
        if (edgeCount && edgeCount < minEdges) {
          minEdges = edgeCount;
          minNode = aLayers.ElementAt(i);
          if (minEdges == 1) {
            break;
          }
        }
      }

      if (minNode) {
        // Remove all of them!
        graph.RemoveEdgesTo(minNode);
        noIncoming.AppendElement(minNode);
      }
    }
  } while (!noIncoming.IsEmpty());
  NS_ASSERTION(!graph.GetEdgeCount(), "Cycles detected!");
#ifdef DEBUG
  if (gDumpLayerSortList) {
    fprintf(stderr, " --- Layers after sorting: --- \n");
    DumpLayerList(sortedList);
  }
#endif

  aLayers.Clear();
  aLayers.AppendElements(sortedList);
}

}
}