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);
}
