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Source/core/page/PrintContext.h

 /*
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2007 Apple Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 22 matching lines @@
 class LocalFrame;
 class FloatRect;
 class FloatSize;
 class GraphicsContext;
 class IntRect;
 class Node;
 
 class PrintContext : public NoBaseWillBeGarbageCollectedFinalized<PrintContext> {
 public:
     explicit PrintContext(LocalFrame*);
     ~PrintContext();

[Vitaly Buka (NO REVIEWS), 2014/08/13 21:17:42]

virtual destructor?

[abarth-chromium, 2014/08/13 21:23:14]

Will do.

 
     LocalFrame* frame() const { return m_frame; }
 
     // Break up a page into rects without relayout.
     // FIXME: This means that CSS page breaks won't be on page boundary if the size is different than what was passed to begin(). That's probably not always desirable.
     // FIXME: Header and footer height should be applied before layout, not after.
     // FIXME: The printRect argument is only used to determine page aspect ratio, it would be better to pass a FloatSize with page dimensions instead.
-    void computePageRects(const FloatRect& printRect, float headerHeight, float footerHeight, float userScaleFactor, float& outPageHeight, bool allowHorizontalTiling = false);
+    virtual void computePageRects(const FloatRect& printRect, float headerHeight, float footerHeight, float userScaleFactor, float& outPageHeight);
 
     // Deprecated. Page size computation is already in this class, clients shouldn't be copying it.
+    // FIXME: Everyone passes |false| for the second paramer. We should remove the second parameter.
     void computePageRectsWithPageSize(const FloatSize& pageSizeInPixels, bool allowHorizontalTiling);

[Vitaly Buka (NO REVIEWS), 2014/08/13 21:43:44]

virtual, because it's also m_pageRects related

and override with NOTREACHED for ChromePrintContext

 
     // These are only valid after page rects are computed.
-    size_t pageCount() const { return m_pageRects.size(); }
+    virtual size_t pageCount() const { return m_pageRects.size(); }
     const IntRect& pageRect(size_t pageNumber) const { return m_pageRects[pageNumber]; }

[Vitaly Buka (NO REVIEWS), 2014/08/13 21:17:42]

pageRect maybe called with incorrect pageNumber if overrided pageCount() returns
different value.

     const Vector<IntRect>& pageRects() const { return m_pageRects; }

[Vitaly Buka (NO REVIEWS), 2014/08/13 21:17:42]

same

[abarth-chromium, 2014/08/13 21:23:14]

That's true.  What do you recommend?

[Vitaly Buka (NO REVIEWS), 2014/08/13 21:43:44]

maybe 
/*no virtual*/ size_t pageCount() const { return pageRects().size(); }

/*no virtual*/ const IntRect& pageRect(size_t pageNumber) const { return
pageRects()[pageNumber]; }

virtual const Vector<IntRect>& pageRects() const { return m_pageRects; }

and overrides pageRects() only 

[Vitaly Buka (NO REVIEWS), 2014/08/13 21:53:27]

Actually even better to do following
all 3 non virtul with no any overrides in ChromePluginPrintContext:
pageCount(), pageRect(size_t pageNumber), pageRects()

but you just need to change following
ChromePluginPrintContext::computePageRects{
m_pageRects.resize(m_plugin->printBegin(m_printParams))
for each rect in m_pageRects rect.size = IntRect(printRect)
}

ChromePluginPrintContext::m_pageCount can be deleted

     // Enter print mode, updating layout for new page size.
     // This function can be called multiple times to apply new print options without going back to screen mode.
     void begin(float width, float height = 0);

[Vitaly Buka (NO REVIEWS), 2014/08/13 21:17:42]

begin should be virtual for consistency

[abarth-chromium, 2014/08/13 21:23:14]

Will do.

 
     // Return to screen mode.
-    void end();
+    virtual void end();
 
     // Used by layout tests.
     static int pageNumberForElement(Element*, const FloatSize& pageSizeInPixels); // Returns -1 if page isn't found.
     static String pageProperty(LocalFrame* frame, const char* propertyName, int pageNumber);
     static bool isPageBoxVisible(LocalFrame* frame, int pageNumber);
     static String pageSizeAndMarginsInPixels(LocalFrame* frame, int pageNumber, int width, int height, int marginTop, int marginRight, int marginBottom, int marginLeft);
     static int numberOfPages(LocalFrame*, const FloatSize& pageSizeInPixels);
 
     virtual void trace(Visitor*);
 
@@ skipping 10 matching lines @@
     // Used to prevent misuses of begin() and end() (e.g., call end without begin).
     bool m_isPrinting;
 
     WillBeHeapHashMap<String, RawPtrWillBeMember<Element> > m_linkedDestinations;
     bool m_linkedDestinationsValid;
 };
 
 }
 
 #endif