Invalidate first line display item clients when first line style changes

third_party/WebKit/Source/core/layout/LayoutInline.cpp

Index: third_party/WebKit/Source/core/layout/LayoutInline.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutInline.cpp b/third_party/WebKit/Source/core/layout/LayoutInline.cpp
index 58f6568fd484ab97715f23e4fbfa2cdac89ef240..fd5bdf89a9bf80156e7d7c9b3a4a60388ac281c4 100644
--- a/third_party/WebKit/Source/core/layout/LayoutInline.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutInline.cpp
@@ -1424,4 +1424,24 @@ void LayoutInline::invalidateDisplayItemClients(const LayoutBoxModelObject& pain
         paintInvalidationContainer.invalidateDisplayItemClientOnBacking(*box, invalidationReason, paintInvalidationRect);
 }
 
+void LayoutInline::invalidateDisplayItemClientsOfFirstLine()
+{
+    if (alwaysCreateLineBoxes()) {
+        for (InlineFlowBox* box = firstLineBox(); box; box = box->nextLineBox()) {
+            if (!box->isFirstLineStyle())
+                break;
+            box->invalidateDisplayItemClientsOfFirstLine();
+        }
+        return;
+    }
+
+    for (LayoutObject* child = firstChild(); child; child = child->nextSibling()) {

[mstensho (USE GERRIT), 2015/12/01 12:29:49]

Looks like there's nothing that stops at the end of the first line here.

<div>
    <span>[lots of text, creating hundreds of lines]</span>
</div>

You'd end up invalidating the entire block in that case, wouldn't you?

Conversely, there doesn't seem to be any check whether this inline occurs on a
first line at all.

I don't think I understand why we want this part of the method at all. I think
it would be better if the code above tried harder to locate line boxes (in case
of !alwaysCreateLineBoxes()). If that's to much work, how about locating the
containing block and call invalidateDisplayItemClientsOfFirstLine() on it
instead? But I think we should ask a line layout expert.

[Xianzhu, 2015/12/01 20:06:25]

I think invalidating the first line of containing block is a good idea. It may
invalidate more but code is much simpler and the over-invalidation doesn't seem
a big issue.

+        child->setShouldDoFullPaintInvalidation();

[chrishtr, 2015/12/01 01:43:11]

Why this line?

+        if (child->isLayoutInline())
+            toLayoutInline(child)->invalidateDisplayItemClientsOfFirstLine();
+        else if (child->isText())
+            toLayoutText(child)->invalidateDisplayItemClientsOfFirstLine();
+    }
+}
+
 } // namespace blink