Preliminary paint property walk implementation for SPv2

third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "config.h"
+#include "core/paint/PaintPropertyTreeBuilder.h"
+
+#include "core/frame/FrameView.h"
+#include "core/layout/LayoutView.h"
+#include "core/paint/ObjectPaintProperties.h"
+#include "core/paint/PaintLayer.h"
+#include "platform/graphics/paint/TransformPaintPropertyNode.h"
+#include "platform/transforms/TransformationMatrix.h"
+
+namespace blink {
+
+struct PaintPropertyTreeBuilder::WalkContext {

[pdr., 2015/10/14 17:52:07]

CurrentPropertyTreeContext?

[trchen, 2015/10/14 22:51:13]

I'm thinking just Context... Being a nested class told us enough information.

+    explicit WalkContext(TransformPaintPropertyNode* newCurrentTransform = nullptr) : currentTransform(newCurrentTransform) { }
+    TransformPaintPropertyNode* currentTransform;
+};
+
+struct PaintPropertyTreeBuilder::WalkContextHTML : public WalkContext {

[pdr., 2015/10/14 17:52:07]

Does this need to be so abstract? What other subclasses will there be? Also,
isn't this the LayoutTree and not HTML/DOM tree?

[trchen, 2015/10/14 22:51:13]

I'm thinking of SVG. They are different because they don't carry paint offset
around, and they don't have the concept of out-of-flow position container.
Anyway I think you are right, at this moment one class should suffice.

+    static WalkContextHTML contextForDocumentNode(TransformPaintPropertyNode* fixed, TransformPaintPropertyNode* absolute) { return WalkContextHTML(fixed, absolute); }
+
+    LayoutPoint paintOffset;
+
+    TransformPaintPropertyNode* transformForOutOfFlowPositioned;
+    LayoutPoint paintOffsetForOutOfFlowPositioned;
+
+    TransformPaintPropertyNode* transformForFixedPositioned;
+    LayoutPoint paintOffsetForFixedPositioned;
+private:
+    WalkContextHTML(TransformPaintPropertyNode* fixed, TransformPaintPropertyNode* absolute)
+        : WalkContext(absolute)
+        , transformForOutOfFlowPositioned(absolute)
+        , transformForFixedPositioned(fixed)
+    {
+    }
+};
+
+void PaintPropertyTreeBuilder::buildPropertyTrees(FrameView& rootFrame)
+{
+    walk(rootFrame, WalkContext());
+}
+
+void PaintPropertyTreeBuilder::walk(FrameView& frameView, const WalkContext& context)
+{
+    ObjectPaintProperties& properties = frameView.ensureObjectPaintProperties();
+
+    TransformationMatrix frameTranslate;
+    frameTranslate.translate(frameView.x(), frameView.y());
+    TransformPaintPropertyNode* transformNodeForSelf = new TransformPaintPropertyNode(frameTranslate, FloatPoint3D(), context.currentTransform);
+    properties.setTransformNodeForSelf(adoptRef(transformNodeForSelf));
+
+    TransformationMatrix frameScroll;
+    frameScroll.translate(-frameView.scrollX(), -frameView.scrollY());
+    TransformPaintPropertyNode* transformNodeForDescendants = new TransformPaintPropertyNode(frameScroll, FloatPoint3D(), transformNodeForSelf);
+    properties.setTransformNodeForDescendants(adoptRef(transformNodeForDescendants));
+
+    if (LayoutView* layoutView = frameView.layoutView())
+        walk(*layoutView, WalkContextHTML::contextForDocumentNode(transformNodeForSelf, transformNodeForDescendants));
+}
+
+static bool shouldCreateTransformNodeForSelf(LayoutBoxModelObject& object)
+{
+    // TODO(trchen): Eliminate PaintLayer dependency.
+    PaintLayer* layer = object.layer();
+    if (!layer)
+        return false;
+
+    return layer->paintsWithTransform(GlobalPaintNormalPhase);
+}
+
+static FloatPoint perspectiveOrigin(const LayoutBox& box)
+{
+    const ComputedStyle& style = box.styleRef();
+
+    FloatSize borderBoxSize(box.size());
+    return FloatPoint(floatValueForLength(style.perspectiveOriginX(), borderBoxSize.width()), floatValueForLength(style.perspectiveOriginY(), borderBoxSize.height()));
+}
+
+void PaintPropertyTreeBuilder::walk(LayoutBoxModelObject& object, const WalkContextHTML& context)
+{
+    ASSERT(object.isBox() != object.isLayoutInline()); // Either or.
+
+    WalkContextHTML localContext(context);
+    RefPtr<TransformPaintPropertyNode> newTransformNodeForSelf;
+    RefPtr<TransformPaintPropertyNode> newTransformNodeForDescendants;
+
+    const ComputedStyle& style = object.styleRef();
+    // TODO(trchen): There is some insanity going on with tables. Double check results.
+    switch (style.position()) {
+    case StaticPosition:
+        break;
+    case RelativePosition:
+        localContext.paintOffset += object.offsetForInFlowPosition();
+        break;
+    case AbsolutePosition:
+        localContext.currentTransform = context.transformForOutOfFlowPositioned;
+        localContext.paintOffset = context.paintOffsetForOutOfFlowPositioned;
+        break;
+    case StickyPosition:
+        localContext.paintOffset += object.offsetForInFlowPosition();
+        break;
+    case FixedPosition:
+        localContext.currentTransform = context.transformForFixedPositioned;
+        localContext.paintOffset = context.paintOffsetForFixedPositioned;
+        break;
+    default:
+        ASSERT_NOT_REACHED();
+    }
+    if (object.isBox())
+        localContext.paintOffset += toLayoutBox(object).locationOffset();
+
+    bool hasTransform = object.isBox() && style.hasTransform();

[pdr., 2015/10/14 18:44:15]

I think it's important to unblock some work that depends on property trees
working. What do you think about just implementing transform, the most basic
support, and then adding fixed/sticky/perspective/etc in followup patches?

[trchen, 2015/10/14 22:51:13]

We need to keep track of paint offset in order to calculate combined transform
from the last transform node. Anyway the work has been done.

I do agree that the function is a bit long and needs to be splitted.

[pdr., 2015/10/15 04:53:52]

In order to land this, we will need a ridiculous number of unittests because we
shouldn't land code that isn't well-tested. It'll be much easier to land just
the most basic transform code with unittests and fixmes for all the rest of this
complexity, then slowly build up support, adding unittests as you go.

[trchen, 2015/10/15 23:24:31]

IMO without paint offset handling the code will be pretty much useless. We won't
get the correct result with even a simple <div style="margin-top:100px;
transform:translateZ(0)">.

Let's just add tests instead.

+    if (shouldCreateTransformNodeForSelf(object)) {
+        TransformationMatrix matrix;
+        if (hasTransform)
+            style.applyTransform(matrix, toLayoutBox(object).size(), ComputedStyle::IncludeTransformOrigin, ComputedStyle::IncludeMotionPath, ComputedStyle::IncludeIndependentTransformProperties);
+        matrix.translateRight(localContext.paintOffset.x(), localContext.paintOffset.y());
+        // TODO(jbroman): Put the real transform origin here, instead of using a
+        // matrix with the origin baked in.
+        newTransformNodeForSelf = adoptRef(new TransformPaintPropertyNode(matrix, FloatPoint3D(), localContext.currentTransform));
+        localContext.currentTransform = newTransformNodeForSelf.get();
+        localContext.paintOffset = LayoutPoint();
+    } else {
+        ASSERT(!hasTransform);
+    }
+
+    if (object.isBox() && style.hasPerspective()) {
+        FloatPoint origin = perspectiveOrigin(toLayoutBox(object));
+        TransformationMatrix matrix;
+        matrix.applyPerspective(style.perspective());
+        matrix.translate(-origin.x(), -origin.y());

[jbroman, 2015/10/14 15:11:58]

TransformationMatrix::applyTransformOrigin

[trchen, 2015/10/14 22:51:13]

Done.

+        matrix.translateRight(origin.x(), origin.y());
+        matrix.translateRight(localContext.paintOffset.x(), localContext.paintOffset.y());
+        newTransformNodeForDescendants = adoptRef(new TransformPaintPropertyNode(matrix, FloatPoint3D(), localContext.currentTransform));
+        localContext.currentTransform = newTransformNodeForDescendants.get();
+        localContext.paintOffset = LayoutPoint();
+    }
+
+    if (style.position() != StaticPosition || hasTransform) {
+        localContext.transformForOutOfFlowPositioned = localContext.currentTransform;
+        localContext.paintOffsetForOutOfFlowPositioned = localContext.paintOffset;
+    }
+
+    if (hasTransform) {
+        localContext.transformForFixedPositioned = localContext.currentTransform;
+        localContext.paintOffsetForFixedPositioned = localContext.paintOffset;
+    }
+
+    if (object.hasOverflowClip()) {
+        PaintLayer* layer = object.layer();
+        ASSERT(layer);
+        DoubleSize scrollOffset = layer->scrollableArea()->scrollOffset();
+        if (!scrollOffset.isZero() || layer->scrollsOverflow()) {
+            TransformationMatrix matrix;
+            matrix.translate(-scrollOffset.width(), -scrollOffset.height());
+            newTransformNodeForDescendants = adoptRef(new TransformPaintPropertyNode(matrix, FloatPoint3D(), localContext.currentTransform));
+            localContext.currentTransform = newTransformNodeForDescendants.get();
+        }
+    }
+
+    if (newTransformNodeForSelf || newTransformNodeForDescendants) {
+        ObjectPaintProperties& properties = object.ensureObjectPaintProperties();
+        properties.setTransformNodeForSelf(newTransformNodeForSelf.release());
+        properties.setTransformNodeForDescendants(newTransformNodeForDescendants.release());
+    } else {
+        object.setObjectPaintProperties(nullptr);
+    }
+
+    if (object.isSVGRoot()) {
+        // TODO(trchen): Implement SVG walk.
+        return;
+    }
+
+    for (LayoutObject* child = object.slowFirstChild(); child; child = child->nextSibling()) {
+        if (child->isText())
+            continue;
+        walk(toLayoutBoxModelObject(*child), localContext);
+    }
+}
+
+} // namespace blink