gecko-dev/layout/base/FrameLayerBuilder.cpp

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/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is Mozilla Corporation code.
*
* The Initial Developer of the Original Code is Mozilla Foundation.
* Portions created by the Initial Developer are Copyright (C) 2010
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Robert O'Callahan <robert@ocallahan.org>
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU General Public License Version 2 or later (the "GPL"), or
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
#include "FrameLayerBuilder.h"
#include "nsDisplayList.h"
#include "nsPresContext.h"
#include "nsLayoutUtils.h"
using namespace mozilla::layers;
namespace mozilla {
namespace {
/**
* This class iterates through a display list tree, descending only into
* nsDisplayClip items, and returns each display item encountered during
* such iteration. Along with each item we also return the clip rect
* accumulated for the item.
*/
class ClippedItemIterator {
public:
ClippedItemIterator(const nsDisplayList* aList)
{
DescendIntoList(aList, nsnull, nsnull);
AdvanceToItem();
}
PRBool IsDone()
{
return mStack.IsEmpty();
}
void Next()
{
State* top = StackTop();
top->mItem = top->mItem->GetAbove();
AdvanceToItem();
}
// Returns null if there is no clipping affecting the item. The
// clip rect is in device pixels
const gfxRect* GetEffectiveClipRect()
{
State* top = StackTop();
return top->mHasClipRect ? &top->mEffectiveClipRect : nsnull;
}
nsDisplayItem* Item()
{
return StackTop()->mItem;
}
private:
// We maintain a stack of state objects. Each State object represents
// where we're up to in the iteration of a list.
struct State {
// The current item we're at in the list
nsDisplayItem* mItem;
// The effective clip rect applying to all the items in this list
gfxRect mEffectiveClipRect;
PRPackedBool mHasClipRect;
};
State* StackTop()
{
return &mStack[mStack.Length() - 1];
}
void DescendIntoList(const nsDisplayList* aList,
nsPresContext* aPresContext,
const nsRect* aClipRect)
{
State* state = mStack.AppendElement();
if (!state)
return;
if (mStack.Length() >= 2) {
*state = mStack[mStack.Length() - 2];
} else {
state->mHasClipRect = PR_FALSE;
}
state->mItem = aList->GetBottom();
if (aClipRect) {
gfxRect r(aClipRect->x, aClipRect->y, aClipRect->width, aClipRect->height);
r.ScaleInverse(aPresContext->AppUnitsPerDevPixel());
if (state->mHasClipRect) {
state->mEffectiveClipRect = state->mEffectiveClipRect.Intersect(r);
} else {
state->mEffectiveClipRect = r;
state->mHasClipRect = PR_TRUE;
}
}
}
// Advances to an item that the iterator should return.
void AdvanceToItem()
{
while (!mStack.IsEmpty()) {
State* top = StackTop();
if (!top->mItem) {
mStack.SetLength(mStack.Length() - 1);
if (!mStack.IsEmpty()) {
top = StackTop();
top->mItem = top->mItem->GetAbove();
}
continue;
}
if (top->mItem->GetType() != nsDisplayItem::TYPE_CLIP)
return;
nsDisplayClip* clipItem = static_cast<nsDisplayClip*>(top->mItem);
nsRect clip = clipItem->GetClipRect();
DescendIntoList(clipItem->GetList(),
clipItem->GetClippingFrame()->PresContext(),
&clip);
}
}
nsAutoTArray<State,10> mStack;
};
/**
* This class represents a sublist of consecutive items in an nsDisplayList.
* The first item in the sublist is mStartItem and the last item
* is the item before mEndItem.
*
* These sublists are themselves organized into a linked list of all
* the ItemGroups associated with a given layer, via mNextItemsForLayer.
* This list will have more than one element if the display items in a layer
* come from different nsDisplayLists, or if they come from the same
* nsDisplayList but they aren't consecutive in that list.
*
* These objects are allocated from the nsDisplayListBuilder arena.
*/
struct ItemGroup {
// If null, then the item group is empty.
nsDisplayItem* mStartItem;
nsDisplayItem* mEndItem;
ItemGroup* mNextItemsForLayer;
// The clipping (if any) that needs to be applied to all these items.
gfxRect mClipRect;
PRPackedBool mHasClipRect;
ItemGroup() : mStartItem(nsnull), mEndItem(nsnull),
mNextItemsForLayer(nsnull), mHasClipRect(PR_FALSE) {}
void* operator new(size_t aSize,
nsDisplayListBuilder* aBuilder) CPP_THROW_NEW {
return aBuilder->Allocate(aSize);
}
};
/**
* This class represents a layer and the display item(s) it
* will render. The items are stored in a linked list of ItemGroups.
*/
struct LayerItems {
nsRefPtr<Layer> mLayer;
// equal to mLayer, or null if mLayer is not a ThebesLayer
ThebesLayer* mThebesLayer;
ItemGroup* mItems;
// The bounds of the visible region for this layer, in device pixels
nsIntRect mVisibleRect;
LayerItems(ItemGroup* aItems) :
mThebesLayer(nsnull), mItems(aItems)
{
}
void* operator new(size_t aSize,
nsDisplayListBuilder* aBuilder) CPP_THROW_NEW {
return aBuilder->Allocate(aSize);
}
};
/**
* Given a (possibly clipped) display item in aItem, try to append it to
* the items in aGroup. If aItem is the next item in the sublist in
* aGroup, and the clipping matches, we can just update aGroup in-place,
* otherwise we'll allocate a new ItemGroup, add it to the linked list,
* and put aItem in the new ItemGroup. We return the ItemGroup into which
* aItem was inserted.
*/
static ItemGroup*
AddToItemGroup(nsDisplayListBuilder* aBuilder,
ItemGroup* aGroup, nsDisplayItem* aItem,
const gfxRect* aClipRect)
{
NS_ASSERTION(!aGroup->mNextItemsForLayer,
"aGroup must be the last group in the chain");
if (!aGroup->mStartItem) {
aGroup->mStartItem = aItem;
aGroup->mEndItem = aItem->GetAbove();
aGroup->mHasClipRect = aClipRect != nsnull;
if (aClipRect) {
aGroup->mClipRect = *aClipRect;
}
return aGroup;
}
if (aGroup->mEndItem == aItem &&
(aGroup->mHasClipRect
? (aClipRect && aGroup->mClipRect == *aClipRect)
: !aClipRect)) {
aGroup->mEndItem = aItem->GetAbove();
return aGroup;
}
ItemGroup* itemGroup = new (aBuilder) ItemGroup();
if (!itemGroup)
return aGroup;
aGroup->mNextItemsForLayer = itemGroup;
return AddToItemGroup(aBuilder, itemGroup, aItem, aClipRect);
}
/**
* Create an empty Thebes layer, with an empty ItemGroup associated with
* it, and append it to aLayers.
*/
static ItemGroup*
CreateEmptyThebesLayer(nsDisplayListBuilder* aBuilder,
LayerManager* aManager,
nsTArray<LayerItems*>* aLayers)
{
ItemGroup* itemGroup = new (aBuilder) ItemGroup();
if (!itemGroup)
return nsnull;
nsRefPtr<ThebesLayer> thebesLayer = aManager->CreateThebesLayer();
if (!thebesLayer)
return nsnull;
LayerItems* layerItems = new (aBuilder) LayerItems(itemGroup);
aLayers->AppendElement(layerItems);
thebesLayer->SetUserData(layerItems);
layerItems->mThebesLayer = thebesLayer;
layerItems->mLayer = thebesLayer.forget();
return itemGroup;
}
static PRBool
IsAllUniform(nsDisplayListBuilder* aBuilder, ItemGroup* aGroup,
nscolor* aColor)
{
nsRect visibleRect = aGroup->mStartItem->GetVisibleRect();
nscolor finalColor = NS_RGBA(0,0,0,0);
for (ItemGroup* group = aGroup; group;
group = group->mNextItemsForLayer) {
for (nsDisplayItem* item = group->mStartItem; item != group->mEndItem;
item = item->GetAbove()) {
nscolor color;
if (visibleRect != item->GetVisibleRect())
return PR_FALSE;
if (!item->IsUniform(aBuilder, &color))
return PR_FALSE;
finalColor = NS_ComposeColors(finalColor, color);
}
}
*aColor = finalColor;
return PR_TRUE;
}
/**
* This is the heart of layout's integration with layers. We
* use a ClippedItemIterator to iterate through descendant display
* items. Each item either has its own layer or is assigned to a
* ThebesLayer. We create ThebesLayers as necessary, although we try
* to put items in the bottom-most ThebesLayer because that is most
* likely to be able to render with an opaque background, which will often
* be required for subpixel text antialiasing to work.
*/
static void BuildLayers(nsDisplayListBuilder* aBuilder,
const nsDisplayList& aList,
LayerManager* aManager,
nsTArray<LayerItems*>* aLayers)
{
NS_ASSERTION(aLayers->IsEmpty(), "aLayers must be initially empty");
// Create "bottom" Thebes layer. We'll try to put as much content
// as possible in this layer because if the container is filled with
// opaque content, this bottommost layer can also be treated as opaque,
// which means content in this layer can have subpixel AA.
// firstThebesLayerItems always points to the last ItemGroup for the
// first Thebes layer.
ItemGroup* firstThebesLayerItems =
CreateEmptyThebesLayer(aBuilder, aManager, aLayers);
if (!firstThebesLayerItems)
return;
// lastThebesLayerItems always points to the last ItemGroup for the
// topmost layer, if it's a ThebesLayer. If the top layer is not a
// Thebes layer, this is null.
ItemGroup* lastThebesLayerItems = firstThebesLayerItems;
// This region contains the bounds of all the content that is above
// the first Thebes layer.
nsRegion areaAboveFirstThebesLayer;
for (ClippedItemIterator iter(&aList); !iter.IsDone(); iter.Next()) {
nsDisplayItem* item = iter.Item();
const gfxRect* clipRect = iter.GetEffectiveClipRect();
// Ask the item if it manages its own layer
nsRefPtr<Layer> layer = item->BuildLayer(aBuilder, aManager);
nsRect bounds = item->GetBounds(aBuilder);
// We set layerItems to point to the LayerItems object where the
// item ends up.
LayerItems* layerItems = nsnull;
if (layer) {
// item has a dedicated layer. Add it to the list, with an ItemGroup
// covering this item only.
ItemGroup* itemGroup = new (aBuilder) ItemGroup();
if (itemGroup) {
AddToItemGroup(aBuilder, itemGroup, item, clipRect);
layerItems = new (aBuilder) LayerItems(itemGroup);
aLayers->AppendElement(layerItems);
if (layerItems) {
if (itemGroup->mHasClipRect) {
gfxRect r = itemGroup->mClipRect;
r.Round();
nsIntRect intRect(r.X(), r.Y(), r.Width(), r.Height());
layer->IntersectClipRect(intRect);
}
layerItems->mLayer = layer.forget();
}
}
// This item is above the first Thebes layer.
areaAboveFirstThebesLayer.Or(areaAboveFirstThebesLayer, bounds);
lastThebesLayerItems = nsnull;
} else {
// No dedicated layer. Add it to a Thebes layer. First try to add
// it to the first Thebes layer, which we can do if there's no
// content between the first Thebes layer and our display item that
// overlaps our display item.
if (!areaAboveFirstThebesLayer.Intersects(bounds)) {
firstThebesLayerItems =
AddToItemGroup(aBuilder, firstThebesLayerItems, item, clipRect);
layerItems = aLayers->ElementAt(0);
} else if (lastThebesLayerItems) {
// Try to add to the last Thebes layer
lastThebesLayerItems =
AddToItemGroup(aBuilder, lastThebesLayerItems, item, clipRect);
// This item is above the first Thebes layer.
areaAboveFirstThebesLayer.Or(areaAboveFirstThebesLayer, bounds);
layerItems = aLayers->ElementAt(aLayers->Length() - 1);
} else {
// Create a new Thebes layer
ItemGroup* itemGroup =
CreateEmptyThebesLayer(aBuilder, aManager, aLayers);
if (itemGroup) {
lastThebesLayerItems =
AddToItemGroup(aBuilder, itemGroup, item, clipRect);
NS_ASSERTION(lastThebesLayerItems == itemGroup,
"AddToItemGroup shouldn't create a new group if the "
"initial group is empty");
// This item is above the first Thebes layer.
areaAboveFirstThebesLayer.Or(areaAboveFirstThebesLayer, bounds);
layerItems = aLayers->ElementAt(aLayers->Length() - 1);
}
}
}
if (layerItems) {
// Update the visible region of the layer to account for the new
// item
nscoord appUnitsPerDevPixel =
item->GetUnderlyingFrame()->PresContext()->AppUnitsPerDevPixel();
layerItems->mVisibleRect.UnionRect(layerItems->mVisibleRect,
item->GetVisibleRect().ToNearestPixels(appUnitsPerDevPixel));
}
}
if (!firstThebesLayerItems->mStartItem) {
// The first Thebes layer has nothing in it. Delete the layer.
// Ensure layer is released.
aLayers->ElementAt(0)->mLayer = nsnull;
aLayers->RemoveElementAt(0);
}
for (PRUint32 i = 0; i < aLayers->Length(); ++i) {
LayerItems* layerItems = aLayers->ElementAt(i);
nscolor color;
// Only convert layers with identity transform to ColorLayers, for now.
// This simplifies the code to set the clip region.
if (layerItems->mThebesLayer &&
IsAllUniform(aBuilder, layerItems->mItems, &color) &&
layerItems->mLayer->GetTransform().IsIdentity()) {
nsRefPtr<ColorLayer> layer = aManager->CreateColorLayer();
layer->SetClipRect(layerItems->mThebesLayer->GetClipRect());
// Clip to mVisibleRect to ensure only the pixels we want are filled.
layer->IntersectClipRect(layerItems->mVisibleRect);
layer->SetColor(gfxRGBA(color));
layerItems->mLayer = layer.forget();
layerItems->mThebesLayer = nsnull;
}
gfxMatrix transform;
nsIntRect visibleRect = layerItems->mVisibleRect;
if (layerItems->mLayer->GetTransform().Is2D(&transform)) {
// if 'transform' is not invertible, then nothing will be displayed
// for the layer, so it doesn't really matter what we do here
transform.Invert();
gfxRect layerVisible = transform.TransformBounds(
gfxRect(visibleRect.x, visibleRect.y, visibleRect.width, visibleRect.height));
layerVisible.RoundOut();
if (NS_FAILED(nsLayoutUtils::GfxRectToIntRect(layerVisible, &visibleRect))) {
NS_ERROR("Visible rect transformed out of bounds");
}
} else {
NS_ERROR("Only 2D transformations currently supported");
}
layerItems->mLayer->SetVisibleRegion(nsIntRegion(visibleRect));
}
}
} // anonymous namespace
already_AddRefed<Layer>
FrameLayerBuilder::MakeContainerLayerFor(nsDisplayListBuilder* aBuilder,
LayerManager* aManager,
nsDisplayItem* aContainer,
const nsDisplayList& aChildren)
{
// If there's only one layer, then in principle we can try to flatten
// things by returning that layer here. But that adds complexity to
// retained layer management so we don't do it. Layer backends can
// flatten internally.
nsRefPtr<ContainerLayer> container = aManager->CreateContainerLayer();
if (!container)
return nsnull;
nsAutoTArray<LayerItems*,10> layerItems;
BuildLayers(aBuilder, aChildren, aManager, &layerItems);
Layer* lastChild = nsnull;
for (PRUint32 i = 0; i < layerItems.Length(); ++i) {
Layer* child = layerItems[i]->mLayer;
container->InsertAfter(child, lastChild);
lastChild = child;
// release the layer now because the ItemGroup destructor doesn't run;
// the container is still holding a reference to it
layerItems[i]->mLayer = nsnull;
}
container->SetIsOpaqueContent(aChildren.IsOpaque());
nsRefPtr<Layer> layer = container.forget();
return layer.forget();
}
/* static */ void
FrameLayerBuilder::DrawThebesLayer(ThebesLayer* aLayer,
gfxContext* aContext,
const nsIntRegion& aRegionToDraw,
const nsIntRegion& aRegionToInvalidate,
void* aCallbackData)
{
// For now, we can ignore aRegionToInvalidate since we don't
// use retained layers.
LayerItems* layerItems = static_cast<LayerItems*>(aLayer->GetUserData());
nsDisplayListBuilder* builder =
static_cast<nsDisplayListBuilder*>(aCallbackData);
// For now, we'll ignore toDraw and just draw the entire visible
// area, because the "visible area" is already confined to just the
// area that needs to be repainted. Later, when we start reusing layers
// from paint to paint, we'll need to pay attention to toDraw and
// actually try to avoid drawing stuff that's not in it.
// Our list may contain content with different prescontexts at
// different zoom levels. 'rc' contains the nsIRenderingContext
// used for the previous display item, and lastPresContext is the
// prescontext for that item. We also cache the clip state for that
// item.
nsRefPtr<nsIRenderingContext> rc;
nsPresContext* lastPresContext = nsnull;
gfxRect currentClip;
PRBool setClipRect = PR_FALSE;
NS_ASSERTION(layerItems->mItems, "No empty layers allowed");
for (ItemGroup* group = layerItems->mItems; group;
group = group->mNextItemsForLayer) {
// If the new desired clip state is different from the current state,
// update the clip.
if (setClipRect != group->mHasClipRect ||
(group->mHasClipRect && group->mClipRect != currentClip)) {
if (setClipRect) {
aContext->Restore();
}
setClipRect = group->mHasClipRect;
if (setClipRect) {
aContext->Save();
aContext->NewPath();
aContext->Rectangle(group->mClipRect, PR_TRUE);
aContext->Clip();
currentClip = group->mClipRect;
}
}
NS_ASSERTION(group->mStartItem, "No empty groups allowed");
for (nsDisplayItem* item = group->mStartItem; item != group->mEndItem;
item = item->GetAbove()) {
nsPresContext* presContext = item->GetUnderlyingFrame()->PresContext();
if (presContext != lastPresContext) {
// Create a new rendering context with the right
// appunits-per-dev-pixel.
nsresult rv =
presContext->DeviceContext()->CreateRenderingContextInstance(*getter_AddRefs(rc));
if (NS_FAILED(rv))
break;
rc->Init(presContext->DeviceContext(), aContext);
lastPresContext = presContext;
}
item->Paint(builder, rc);
}
}
if (setClipRect) {
aContext->Restore();
}
}
} // namespace mozilla