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::Context {

[pdr., 2015/10/20 22:02:30]

Lets doc this with a small comment describing why it's necessary.

[jbroman, 2015/10/20 23:50:13]

I'd also like a brief explanation of how it works. It seems like this is
propagated down the layout tree, but I'd like it to be explicit. A brief
explanation of what "transformForOutOfFlowPositioned" means (I think it's the
transform node that applies to absolute- and relative-positioned kids based on
the description, but I'd have to find the uses to check that).

[trchen, 2015/10/21 06:16:20]

Done.

+    Context() : currentTransform(nullptr), transformForOutOfFlowPositioned(nullptr), transformForFixedPositioned(nullptr) { }
+
+    TransformPaintPropertyNode* currentTransform;
+    LayoutPoint paintOffset;
+
+    TransformPaintPropertyNode* transformForOutOfFlowPositioned;
+    LayoutPoint paintOffsetForOutOfFlowPositioned;
+
+    TransformPaintPropertyNode* transformForFixedPositioned;
+    LayoutPoint paintOffsetForFixedPositioned;
+};
+
+void PaintPropertyTreeBuilder::buildPropertyTrees(FrameView& rootFrame)
+{
+    walk(rootFrame, Context());
+}
+
+void PaintPropertyTreeBuilder::walk(FrameView& frameView, const Context& context)
+{
+    Context localContext(context);
+    RefPtr<TransformPaintPropertyNode> newTransformNodeForPreTranslation;

[pdr., 2015/10/20 22:02:30]

In this function only, lets move these decls down to where they are used.

i.e.,
RefPtr<TranformPaintPropertyNode> newTransformNodeForPreTranslation =
TransformPaintPropertyNode::create(frameTranslate, FloatPoint3D(),
context.currentTransform);

[trchen, 2015/10/21 06:16:20]

Done.

+    RefPtr<TransformPaintPropertyNode> newTransformNodeForScrollTranslation;
+
+    TransformationMatrix frameTranslate;
+    frameTranslate.translate(frameView.x(), frameView.y());
+    // The frame owner applies paint offset already.
+    // This assumption may change in the future.
+    ASSERT(context.paintOffset == LayoutPoint());
+    newTransformNodeForPreTranslation = TransformPaintPropertyNode::create(frameTranslate, FloatPoint3D(), context.currentTransform);
+    localContext.transformForFixedPositioned = newTransformNodeForPreTranslation.get();
+    localContext.paintOffsetForFixedPositioned = LayoutPoint();
+
+    // This is going away in favor of Settings::rootLayerScrolls.
+    DoubleSize scrollOffset = frameView.scrollOffsetDouble();
+    TransformationMatrix frameScroll;
+    frameScroll.translate(-scrollOffset.width(), -scrollOffset.height());
+    newTransformNodeForScrollTranslation = TransformPaintPropertyNode::create(frameScroll, FloatPoint3D(), newTransformNodeForPreTranslation);
+    localContext.currentTransform = localContext.transformForOutOfFlowPositioned = newTransformNodeForScrollTranslation.get();
+    localContext.paintOffset = localContext.paintOffsetForOutOfFlowPositioned = LayoutPoint();
+
+    frameView.setPreTranslation(newTransformNodeForPreTranslation.release());
+    frameView.setScrollTranslation(newTransformNodeForScrollTranslation.release());
+
+    if (LayoutView* layoutView = frameView.layoutView())
+        walk(*layoutView, localContext);
+}
+
+static bool shouldCreatePreTranslationNode(LayoutBoxModelObject& object)
+{
+    // TODO(trchen): Eliminate PaintLayer dependency.
+    PaintLayer* layer = object.layer();
+    if (!layer)
+        return false;
+
+    return layer->paintsWithTransform(GlobalPaintNormalPhase);
+}
+
+static FloatPoint3D transformOrigin(const LayoutBox& box)
+{
+    const ComputedStyle& style = box.styleRef();
+
+    FloatSize borderBoxSize(box.size());
+    return FloatPoint3D(floatValueForLength(style.transformOriginX(), borderBoxSize.width()), floatValueForLength(style.transformOriginY(), borderBoxSize.height()), style.transformOriginZ());

[pdr., 2015/10/20 22:02:30]

Can you break this line so it's a little easier to read?
    return FloatPoint3D(
        floatValueForLength(style.transformOriginX(), borderBoxSize.width()),
        floatValueForLength(style.transformOriginY(), borderBoxSize.height()),
        style.transformOriginZ());

(similarly for perspectiveOrigin below).

[trchen, 2015/10/21 06:16:20]

Done.

+}
+
+static FloatPoint perspectiveOrigin(const LayoutBox& box)
+{
+    const ComputedStyle& style = box.styleRef();
+

[jbroman, 2015/10/20 23:50:13]

super-nit: remove this newline?

[trchen, 2015/10/21 06:16:20]

Done.

+    FloatSize borderBoxSize(box.size());
+    return FloatPoint(floatValueForLength(style.perspectiveOriginX(), borderBoxSize.width()), floatValueForLength(style.perspectiveOriginY(), borderBoxSize.height()));
+}
+
+void PaintPropertyTreeBuilder::walk(LayoutBoxModelObject& object, const Context& context)
+{
+    ASSERT(object.isBox() != object.isLayoutInline()); // Either or.

[pdr., 2015/10/20 22:02:30]

There are many checks for isBox() in this function. In what cases would we need
to support layout inlines at all? Can you add a test for inlines?

[trchen, 2015/10/21 06:16:20]

Yea... Many CSS properties don't apply on inlines. I was surprised to see
transform is forced to none on inlines, and position:absolute forces inlines to
become blocks.

I think the only thing in effect is position:relative. Will add a test for that.

+
+    Context localContext(context);
+    RefPtr<TransformPaintPropertyNode> newTransformNodeForPreTranslation;
+    RefPtr<TransformPaintPropertyNode> newTransformNodeForTransform;
+    RefPtr<TransformPaintPropertyNode> newTransformNodeForPerspective;
+    RefPtr<TransformPaintPropertyNode> newTransformNodeForScrollTranslation;
+
+    // Step 1: Figure out the layout space of the current object.
+    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();
+
+    // Step 2: Create a transform node to consolidate paint offset (if needed).
+    if (shouldCreatePreTranslationNode(object) && localContext.paintOffset != LayoutPoint()) {
+        TransformationMatrix matrix;
+        matrix.translate(localContext.paintOffset.x(), localContext.paintOffset.y());
+        newTransformNodeForPreTranslation = TransformPaintPropertyNode::create(matrix, FloatPoint3D(), localContext.currentTransform);
+        localContext.currentTransform = newTransformNodeForPreTranslation.get();
+        localContext.paintOffset = LayoutPoint();
+    }
+
+    // Step 3: Create a transform node for CSS transform (if presents).

[pdr., 2015/10/20 22:02:30]

Nit: "if presents" -> "if present" (here, and below).

[trchen, 2015/10/21 06:16:20]

Done.

+    bool hasTransform = object.isBox() && style.hasTransform();
+    if (hasTransform) {
+        TransformationMatrix matrix;
+        style.applyTransform(matrix, toLayoutBox(object).size(), ComputedStyle::ExcludeTransformOrigin, ComputedStyle::IncludeMotionPath, ComputedStyle::IncludeIndependentTransformProperties);

[jbroman, 2015/10/20 23:50:13]

nit: Mind wrapping some of these long lines? I know blink has no line limit, but
192 cols is pushing it.

[trchen, 2015/10/21 06:16:20]

Done.

+        newTransformNodeForTransform = TransformPaintPropertyNode::create(matrix, transformOrigin(toLayoutBox(object)), localContext.currentTransform);
+        localContext.currentTransform = newTransformNodeForTransform.get();
+        ASSERT(localContext.paintOffset == LayoutPoint());
+    }
+    // At this point, the current space is the space we paint the element itself.
+
+    // Step 3: Create a transform node for CSS perspective (if presents).

[jbroman, 2015/10/20 23:50:13]

nit: There are two step 3s. I would probably remove the numbers as otherwise
we'll have to renumber every time we add, remove or reorder steps.

[trchen, 2015/10/21 06:16:20]

Done.

+    if (object.isBox() && style.hasPerspective()) {
+        TransformationMatrix matrix;
+        matrix.applyPerspective(style.perspective());
+        newTransformNodeForPerspective = TransformPaintPropertyNode::create(matrix, perspectiveOrigin(toLayoutBox(object)) + toLayoutSize(localContext.paintOffset), localContext.currentTransform);
+        localContext.currentTransform = newTransformNodeForPerspective.get();
+    }
+
+    // Step 4: Create a transform node for overflow clip (if presents).
+    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());
+            newTransformNodeForScrollTranslation = TransformPaintPropertyNode::create(matrix, FloatPoint3D(), localContext.currentTransform);
+            localContext.currentTransform = newTransformNodeForScrollTranslation.get();
+        }
+    }
+    // At this point, the current space is the space we paint in-flow children.
+
+    // Step 5: Update the context for out-of-flow descendants (if position container is established).
+    if (style.position() != StaticPosition || hasTransform) {

[jbroman, 2015/10/20 23:50:13]

Does the logic for what creates a containing block for absolute and fixed stuff
exist elsewhere in a reusable way, or not? I'm afraid of this diverging from
what other parts of the code assume.

(If not, I guess we could punt that cleanup until later.)

[trchen, 2015/10/21 06:16:20]

Nope, any divergence is unintentional. shouldCreatePreTranslationNode() above
invokes PaintLayer counterpart to ensure we stay in consistent with PaintLayer.

+        localContext.transformForOutOfFlowPositioned = localContext.currentTransform;
+        localContext.paintOffsetForOutOfFlowPositioned = localContext.paintOffset;
+    }
+    if (hasTransform) {
+        localContext.transformForFixedPositioned = localContext.currentTransform;
+        localContext.paintOffsetForFixedPositioned = localContext.paintOffset;
+    }
+
+    // Step 6: Memorize the nodes we created for future reference during paint.
+    if (newTransformNodeForPreTranslation || newTransformNodeForTransform || newTransformNodeForPerspective || newTransformNodeForScrollTranslation) {
+        ObjectPaintProperties& properties = object.ensureObjectPaintProperties();
+        properties.setPreTranslation(newTransformNodeForPreTranslation.release());
+        properties.setTransform(newTransformNodeForTransform.release());
+        properties.setPerspective(newTransformNodeForPerspective.release());
+        properties.setScrollTranslation(newTransformNodeForScrollTranslation.release());
+    } else {
+        object.clearObjectPaintProperties();
+    }
+
+    // Step 7: Recur.
+    if (object.isSVGRoot()) {

[pdr., 2015/10/20 22:02:30]

Nit:
// TODO(trchen): Implement the SVG transform walk.
if (object.isSVGRoot())
    return;

[trchen, 2015/10/21 06:16:20]

Done.

+        // TODO(trchen): Implement SVG walk.
+        return;
+    }
+
+    for (LayoutObject* child = object.slowFirstChild(); child; child = child->nextSibling()) {

[pdr., 2015/10/20 22:02:30]

Lets move the recur comment here.

[trchen, 2015/10/21 06:16:20]

Nah, for SVG walk it is going to recur too. Just that we can't assume the
children to be LayoutBoxModelObject, and need to do some adjustment to the
context.

Other things need to be added here as well, for example LayoutFrame needs to
walk the sub-frame.

+        if (child->isText())
+            continue;
+        walk(toLayoutBoxModelObject(*child), localContext);
+    }
+}
+
+} // namespace blink