SkDocument base for pdf, xps, etc.

include/core/SkDocument.h

Index: include/core/SkDocument.h
diff --git a/include/core/SkDocument.h b/include/core/SkDocument.h
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+++ b/include/core/SkDocument.h
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+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkDocument_DEFINED
+#define SkDocument_DEFINED
+
+#include "SkRect.h"
+#include "SkRefCnt.h"
+
+class SkCanvas;
+class SkWStream;
+
+/**
+ *  High-level API for creating a document-based canvas. To use..
+ *
+ *  1. Create a document, specifying a stream to store the output.
+ *  2. For each "page" of content:
+ *      a. canvas = doc->beginPage(...)
+ *      b. draw_my_content(canvas);
+ *      c. doc->endPage();
+ *  3. Close the document with doc->close().
+ */
+class SkDocument : public SkRefCnt {
+public:
+    /**
+     *  Create a PDF-backed document, writing the results into a file. If there
+     *  is an error trying to create the doc, returns NULL.
+     */
+    static SkDocument* CreatePDF(const char filename[]);
+
+    /**
+     *  Create a PDF-backed document, writing the results into a stream.
+     *  there is an error trying to create the doc, returns NULL.

[scroggo, 2013/06/07 20:12:32]

If got lost here.

+     *
+     *  The document may write to the stream at anytime during its lifetime,
+     *  until either close() is called or the document is deleted. Thus the
+     *  caller must ensure that the stream remains in scope.
+     */
+    static SkDocument* CreatePDF(SkWStream*);
+
+    /**
+     *  Begin a new page for the document, returning the canvas that will draw
+     *  into the page. The document owns this canvas, and it will go out of
+     *  scope when endPage() or close() is called, or the document is deleted.
+     */
+    SkCanvas* beginPage(SkScalar width, SkScalar height,
+                        const SkRect* content = NULL);
+
+    /**
+     *  Call endPage() when the content for the current page has been drawn
+     *  (into the canvas returned by beginPage()). After this call the canvas
+     *  returned by beginPage() will be out-of-scope.
+     */
+    void endPage();
+
+    /**
+     *  Call close() when all pages have been drawn. This will close the file
+     *  or stream holding the document's contents. After close() the document
+     *  can no longer add new pages. Deleting the document will automatically
+     *  call close() if need be.
+     */
+    void close();
+
+protected:
+    SkDocument(SkWStream*);
+    virtual ~SkDocument();
+
+    virtual SkCanvas* onBeginPage(SkScalar width, SkScalar height,
+                                  const SkRect& content) = 0;
+    virtual void onEndPage() = 0;
+    virtual void onClose(SkWStream*) = 0;
+
+    enum State {
+        kBetweenPages_State,
+        kInPage_State,
+        kClosed_State
+    };
+    State getState() const { return fState; }
+
+private:
+    SkWStream* fStream;
+    State      fState;    
+};
+
+#endif