[Line Layout API] Some harder SVGTextLayoutEngine changes

third_party/WebKit/Source/core/svg/SVGTextContentElement.cpp

Index: third_party/WebKit/Source/core/svg/SVGTextContentElement.cpp
diff --git a/third_party/WebKit/Source/core/svg/SVGTextContentElement.cpp b/third_party/WebKit/Source/core/svg/SVGTextContentElement.cpp
index 7f134aca6fdab2c5f0ed47e0f1936b624bf86703..feb591fe1d108d349de704c482d1e02b3a9054b1 100644
--- a/third_party/WebKit/Source/core/svg/SVGTextContentElement.cpp
+++ b/third_party/WebKit/Source/core/svg/SVGTextContentElement.cpp
@@ -31,6 +31,7 @@
 #include "core/frame/LocalFrame.h"
 #include "core/frame/UseCounter.h"
 #include "core/layout/LayoutObject.h"
+#include "core/layout/api/LineLayoutAPIShim.h"
 #include "core/layout/svg/SVGTextQuery.h"
 
 namespace blink {
@@ -250,15 +251,12 @@ bool SVGTextContentElement::selfHasRelativeLengths() const
     return true;
 }
 
-SVGTextContentElement* SVGTextContentElement::elementFromLayoutObject(LayoutObject* layoutObject)
+SVGTextContentElement* SVGTextContentElement::elementFromLineLayoutItem(LineLayoutItem lineLayoutItem)
 {
-    if (!layoutObject)

[pilgrim_google, 2016/02/11 18:19:28]

Yeah, that worries me too. Levi needs to weigh in on whether this is acceptable,
or how we should solve it. I don't remember if the magical operators we put on
LineLayoutItem extend to null checks, or if we would need to code a specific
isNull() method to check the underlying LayoutObject.

[dgrogan, 2016/02/11 19:12:33]

What operators are you referring to? I only see 1:
operator LayoutObject*() const { return m_layoutObject; }

The more I think about it, I don't see how we can guarantee the underlying
object isn't null; I think we need to expose an isNull(). But I'd love it if
Levi somehow knew that we didn't.

[leviw_travelin_and_unemployed, 2016/02/11 21:35:02]

Ahh, allow me to introduce you to the magical world of UnspecifiedBoolType!
https://code.google.com/p/chromium/codesearch#search/&q=UnspecifiedBoolType&s...

LineLayoutItem needs to have an operator UnspecifiedBoolType(). You can use any
of the other versions as a guide :)

[dgrogan, 2016/02/11 23:36:02]

For anyone following along at home, Levi and I discussed on chat: having both
UnspecifiedBoolType AND LayoutObject* operator() brings unknown complexity and
there are enough uses non-bool uses of the operator that we should eliminate
them in a separate patch. Then when they are gone we can replace isNull() and
LayoutObject* operator() with UnspecifiedBoolType.

Or C++11 will have possibly saved us by then and we can just use explicit
operator bool() instead of UnspecifiedBoolType hackery. But I've already passed
the frontier of my C++ knowledge.

+    if (!lineLayoutItem.isSVGText() && !lineLayoutItem.isSVGInline())
         return nullptr;
 
-    if (!layoutObject->isSVGText() && !layoutObject->isSVGInline())
-        return nullptr;
-
-    SVGElement* element = toSVGElement(layoutObject->node());
+    SVGElement* element = toSVGElement(lineLayoutItem.node());
     ASSERT(element);
     return isSVGTextContentElement(*element) ? toSVGTextContentElement(element) : 0;
 }