LCOV - code coverage report
Current view: directory - gfx/layers - LayerSorter.cpp (source / functions) Found Hit Coverage
Test: app.info Lines: 116 2 1.7 %
Date: 2012-06-02 Functions: 8 2 25.0 %

       1                 : /* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
       2                 :  * ***** BEGIN LICENSE BLOCK *****
       3                 :  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
       4                 :  *
       5                 :  * The contents of this file are subject to the Mozilla Public License Version
       6                 :  * 1.1 (the "License"); you may not use this file except in compliance with
       7                 :  * the License. You may obtain a copy of the License at
       8                 :  * http://www.mozilla.org/MPL/
       9                 :  *
      10                 :  * Software distributed under the License is distributed on an "AS IS" basis,
      11                 :  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
      12                 :  * for the specific language governing rights and limitations under the
      13                 :  * License.
      14                 :  *
      15                 :  * The Original Code is Mozilla Corporation code.
      16                 :  *
      17                 :  * The Initial Developer of the Original Code is Mozilla Foundation.
      18                 :  * Portions created by the Initial Developer are Copyright (C) 2011
      19                 :  * the Initial Developer. All Rights Reserved.
      20                 :  *
      21                 :  * Contributor(s):
      22                 :  *   Matt Woodrow <mwoodrow@mozilla.com>
      23                 :  *
      24                 :  * Alternatively, the contents of this file may be used under the terms of
      25                 :  * either the GNU General Public License Version 2 or later (the "GPL"), or
      26                 :  * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
      27                 :  * in which case the provisions of the GPL or the LGPL are applicable instead
      28                 :  * of those above. If you wish to allow use of your version of this file only
      29                 :  * under the terms of either the GPL or the LGPL, and not to allow others to
      30                 :  * use your version of this file under the terms of the MPL, indicate your
      31                 :  * decision by deleting the provisions above and replace them with the notice
      32                 :  * and other provisions required by the GPL or the LGPL. If you do not delete
      33                 :  * the provisions above, a recipient may use your version of this file under
      34                 :  * the terms of any one of the MPL, the GPL or the LGPL.
      35                 :  *
      36                 :  * ***** END LICENSE BLOCK ***** */
      37                 : 
      38                 : #include "LayerSorter.h"
      39                 : #include "DirectedGraph.h"
      40                 : #include "limits.h"
      41                 : #include "gfxLineSegment.h"
      42                 : 
      43                 : namespace mozilla {
      44                 : namespace layers {
      45                 : 
      46                 : enum LayerSortOrder {
      47                 :   Undefined,
      48                 :   ABeforeB,
      49                 :   BBeforeA,
      50                 : };
      51                 : 
      52                 : /**
      53                 :  * Recover the z component from a 2d transformed point by finding the intersection
      54                 :  * of a line through the point in the z direction and the transformed plane.
      55                 :  *
      56                 :  * We want to solve:
      57                 :  *
      58                 :  * point = normal . (p0 - l0) / normal . l
      59                 :  */
      60               0 : static gfxFloat RecoverZDepth(const gfx3DMatrix& aTransform, const gfxPoint& aPoint)
      61                 : {
      62               0 :     const gfxPoint3D l(0, 0, 1);
      63               0 :     gfxPoint3D l0 = gfxPoint3D(aPoint.x, aPoint.y, 0);
      64               0 :     gfxPoint3D p0 = aTransform.Transform3D(gfxPoint3D(0, 0, 0));
      65               0 :     gfxPoint3D normal = aTransform.GetNormalVector();
      66                 : 
      67               0 :     gfxFloat n = normal.DotProduct(p0 - l0); 
      68               0 :     gfxFloat d = normal.DotProduct(l);
      69                 : 
      70               0 :     if (!d) {
      71               0 :         return 0;
      72                 :     }
      73                 : 
      74               0 :     return n/d;
      75                 : }
      76                 : 
      77                 : /**
      78                 :  * Determine if this transform layer should be drawn before another when they 
      79                 :  * are both preserve-3d children.
      80                 :  *
      81                 :  * We want to find the relative z depths of the 2 layers at points where they
      82                 :  * intersect when projected onto the 2d screen plane. Intersections are defined
      83                 :  * as corners that are positioned within the other quad, as well as intersections
      84                 :  * of the lines.
      85                 :  *
      86                 :  * We then choose the intersection point with the greatest difference in Z
      87                 :  * depths and use this point to determine an ordering for the two layers.
      88                 :  * For layers that are intersecting in 3d space, this essentially guesses an 
      89                 :  * order. In a lot of cases we only intersect right at the edge point (3d cubes
      90                 :  * in particular) and this generates the 'correct' looking ordering. For planes
      91                 :  * that truely intersect, then there is no correct ordering and this remains
      92                 :  * unsolved without changing our rendering code.
      93                 :  */
      94               0 : static LayerSortOrder CompareDepth(Layer* aOne, Layer* aTwo) {
      95               0 :   gfxRect ourRect = aOne->GetEffectiveVisibleRegion().GetBounds();
      96               0 :   gfxRect otherRect = aTwo->GetEffectiveVisibleRegion().GetBounds();
      97                 : 
      98               0 :   gfx3DMatrix ourTransform = aOne->GetTransform();
      99               0 :   gfx3DMatrix otherTransform = aTwo->GetTransform();
     100                 : 
     101                 :   // Transform both rectangles and project into 2d space.
     102               0 :   gfxQuad ourTransformedRect = ourTransform.TransformRect(ourRect);
     103               0 :   gfxQuad otherTransformedRect = otherTransform.TransformRect(otherRect);
     104                 : 
     105               0 :   gfxRect ourBounds = ourTransformedRect.GetBounds();
     106               0 :   gfxRect otherBounds = otherTransformedRect.GetBounds();
     107                 : 
     108               0 :   if (!ourBounds.Intersects(otherBounds)) {
     109               0 :     return Undefined;
     110                 :   }
     111                 : 
     112                 :   // Make a list of all points that are within the other rect.
     113                 :   // Could we just check Contains() on the bounds rects. ie, is it possible
     114                 :   // for layers to overlap without intersections (in 2d space) and yet still
     115                 :   // have their bounds rects not completely enclose each other?
     116               0 :   nsTArray<gfxPoint> points;
     117               0 :   for (PRUint32 i = 0; i < 4; i++) {
     118               0 :     if (ourTransformedRect.Contains(otherTransformedRect.mPoints[i])) {
     119               0 :       points.AppendElement(otherTransformedRect.mPoints[i]);
     120                 :     }
     121               0 :     if (otherTransformedRect.Contains(ourTransformedRect.mPoints[i])) {
     122               0 :       points.AppendElement(ourTransformedRect.mPoints[i]);
     123                 :     }
     124                 :   }
     125                 :   
     126                 :   // Look for intersections between lines (in 2d space) and use these as
     127                 :   // depth testing points.
     128               0 :   for (PRUint32 i = 0; i < 4; i++) {
     129               0 :     for (PRUint32 j = 0; j < 4; j++) {
     130               0 :       gfxPoint intersection;
     131                 :       gfxLineSegment one(ourTransformedRect.mPoints[i],
     132               0 :                          ourTransformedRect.mPoints[(i + 1) % 4]);
     133                 :       gfxLineSegment two(otherTransformedRect.mPoints[j],
     134               0 :                          otherTransformedRect.mPoints[(j + 1) % 4]);
     135               0 :       if (one.Intersects(two, intersection)) {
     136               0 :         points.AppendElement(intersection);
     137                 :       }
     138                 :     }
     139                 :   }
     140                 : 
     141                 :   // No intersections, no defined order between these layers.
     142               0 :   if (points.IsEmpty()) {
     143               0 :     return Undefined;
     144                 :   }
     145                 : 
     146                 :   // Find the relative Z depths of each intersection point and check that the layers are in the same order.
     147               0 :   gfxFloat highest = 0;
     148               0 :   for (PRUint32 i = 0; i < points.Length(); i++) {
     149               0 :     gfxFloat ourDepth = RecoverZDepth(ourTransform, points.ElementAt(i));
     150               0 :     gfxFloat otherDepth = RecoverZDepth(otherTransform, points.ElementAt(i));
     151                 : 
     152               0 :     gfxFloat difference = otherDepth - ourDepth;
     153                 : 
     154               0 :     if (fabs(difference) > fabs(highest)) {
     155               0 :       highest = difference;
     156                 :     }
     157                 :   }
     158                 :   // If layers have the same depth keep the original order
     159               0 :   if (highest >= 0) {
     160               0 :     return ABeforeB;
     161                 :   } else {
     162               0 :     return BBeforeA;
     163                 :   }
     164                 : }
     165                 : 
     166                 : #ifdef DEBUG
     167            1464 : static bool gDumpLayerSortList = getenv("MOZ_DUMP_LAYER_SORT_LIST") != 0;
     168                 : 
     169               0 : static void DumpLayerList(nsTArray<Layer*>& aLayers)
     170                 : {
     171               0 :   for (PRUint32 i = 0; i < aLayers.Length(); i++) {
     172               0 :     fprintf(stderr, "%p, ", aLayers.ElementAt(i));
     173                 :   }
     174               0 :   fprintf(stderr, "\n");
     175               0 : }
     176                 : 
     177               0 : static void DumpEdgeList(DirectedGraph<Layer*>& aGraph)
     178                 : {
     179               0 :   nsTArray<DirectedGraph<Layer*>::Edge> edges = aGraph.GetEdgeList();
     180                 :   
     181               0 :   for (PRUint32 i = 0; i < edges.Length(); i++) {
     182               0 :     fprintf(stderr, "From: %p, To: %p\n", edges.ElementAt(i).mFrom, edges.ElementAt(i).mTo);
     183                 :   }
     184               0 : }
     185                 : #endif
     186                 : 
     187                 : // The maximum number of layers that we will attempt to sort. Anything
     188                 : // greater than this will be left unsorted. We should consider enabling
     189                 : // depth buffering for the scene in this case.
     190                 : #define MAX_SORTABLE_LAYERS 100
     191                 : 
     192               0 : void SortLayersBy3DZOrder(nsTArray<Layer*>& aLayers)
     193                 : {
     194               0 :   PRUint32 nodeCount = aLayers.Length();
     195               0 :   if (nodeCount > MAX_SORTABLE_LAYERS) {
     196               0 :     return;
     197                 :   }
     198               0 :   DirectedGraph<Layer*> graph;
     199                 : 
     200                 : #ifdef DEBUG
     201               0 :   if (gDumpLayerSortList) {
     202               0 :     fprintf(stderr, " --- Layers before sorting: --- \n");
     203               0 :     DumpLayerList(aLayers);
     204                 :   }
     205                 : #endif
     206                 : 
     207                 :   // Iterate layers and determine edges.
     208               0 :   for (PRUint32 i = 0; i < nodeCount; i++) {
     209               0 :     for (PRUint32 j = i + 1; j < nodeCount; j++) {
     210               0 :       Layer* a = aLayers.ElementAt(i);
     211               0 :       Layer* b = aLayers.ElementAt(j);
     212               0 :       LayerSortOrder order = CompareDepth(a, b);
     213               0 :       if (order == ABeforeB) {
     214               0 :         graph.AddEdge(a, b);
     215               0 :       } else if (order == BBeforeA) {
     216               0 :         graph.AddEdge(b, a);
     217                 :       }
     218                 :     }
     219                 :   }
     220                 : 
     221                 : #ifdef DEBUG
     222               0 :   if (gDumpLayerSortList) {
     223               0 :     fprintf(stderr, " --- Edge List: --- \n");
     224               0 :     DumpEdgeList(graph);
     225                 :   }
     226                 : #endif
     227                 : 
     228                 :   // Build a new array using the graph.
     229               0 :   nsTArray<Layer*> noIncoming;
     230               0 :   nsTArray<Layer*> sortedList;
     231                 : 
     232                 :   // Make a list of all layers with no incoming edges.
     233               0 :   noIncoming.AppendElements(aLayers);
     234               0 :   const nsTArray<DirectedGraph<Layer*>::Edge>& edges = graph.GetEdgeList();
     235               0 :   for (PRUint32 i = 0; i < edges.Length(); i++) {
     236               0 :     noIncoming.RemoveElement(edges.ElementAt(i).mTo);
     237                 :   }
     238                 : 
     239                 :   // Move each item without incoming edges into the sorted list,
     240                 :   // and remove edges from it.
     241               0 :   do {
     242               0 :     if (!noIncoming.IsEmpty()) {
     243               0 :       PRUint32 last = noIncoming.Length() - 1;
     244                 : 
     245               0 :       Layer* layer = noIncoming.ElementAt(last);
     246                 : 
     247               0 :       noIncoming.RemoveElementAt(last);
     248               0 :       sortedList.AppendElement(layer);
     249                 : 
     250               0 :       nsTArray<DirectedGraph<Layer*>::Edge> outgoing;
     251               0 :       graph.GetEdgesFrom(layer, outgoing);
     252               0 :       for (PRUint32 i = 0; i < outgoing.Length(); i++) {
     253               0 :         DirectedGraph<Layer*>::Edge edge = outgoing.ElementAt(i);
     254               0 :         graph.RemoveEdge(edge);
     255               0 :         if (!graph.NumEdgesTo(edge.mTo)) {
     256                 :           // If this node also has no edges now, add it to the list
     257               0 :           noIncoming.AppendElement(edge.mTo);
     258                 :         }
     259                 :       }
     260                 :     }
     261                 : 
     262                 :     // If there are no nodes without incoming edges, but there
     263                 :     // are still edges, then we have a cycle.
     264               0 :     if (noIncoming.IsEmpty() && graph.GetEdgeCount()) {
     265                 :       // Find the node with the least incoming edges.
     266               0 :       PRUint32 minEdges = UINT_MAX;
     267               0 :       Layer* minNode = nsnull;
     268               0 :       for (PRUint32 i = 0; i < aLayers.Length(); i++) {
     269               0 :         PRUint32 edgeCount = graph.NumEdgesTo(aLayers.ElementAt(i));
     270               0 :         if (edgeCount && edgeCount < minEdges) {
     271               0 :           minEdges = edgeCount;
     272               0 :           minNode = aLayers.ElementAt(i);
     273               0 :           if (minEdges == 1) {
     274               0 :             break;
     275                 :           }
     276                 :         }
     277                 :       }
     278                 : 
     279                 :       // Remove all of them!
     280               0 :       graph.RemoveEdgesTo(minNode);
     281               0 :       noIncoming.AppendElement(minNode);
     282                 :     }
     283               0 :   } while (!noIncoming.IsEmpty());
     284               0 :   NS_ASSERTION(!graph.GetEdgeCount(), "Cycles detected!");
     285                 : #ifdef DEBUG
     286               0 :   if (gDumpLayerSortList) {
     287               0 :     fprintf(stderr, " --- Layers after sorting: --- \n");
     288               0 :     DumpLayerList(sortedList);
     289                 :   }
     290                 : #endif
     291                 : 
     292               0 :   aLayers.Clear();
     293               0 :   aLayers.AppendElements(sortedList);
     294                 : }
     295                 : 
     296                 : }
     297            4392 : }

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