pdfviewer: more code comments + concat the pdf matrix with the existing matrix in canvas, instead o…

experimental/PdfViewer/SkPdfRenderer.h

Index: experimental/PdfViewer/SkPdfRenderer.h
===================================================================
--- experimental/PdfViewer/SkPdfRenderer.h	(revision 11730)
+++ experimental/PdfViewer/SkPdfRenderer.h	(working copy)
@@ -19,50 +19,67 @@
 class SkStream;
 class SkString;
 
+// What kind of content to render.
 enum SkPdfContent {
     kNoForms_SkPdfContent,
     kAll_SkPdfContent,
 };
 
-// TODO(edisonn): add options to render forms, checkboxes, ...
-// TODO(edisonn): Add API for Forms viewing and editing
-// e.g. SkBitmap getPage(int page);
-//      int formsCount();
-//      SkForm getForm(int formID); // SkForm(SkRect, .. other data)
-// TODO (edisonn): Add intend when loading pdf, for example: for viewing, for parsing content, ...
-
+/** \class SkPdfRenderer
+ *
+ *  The SkPdfRenderer class is used to render a PDF into canvas.
+ *
+ */
 class SkPdfRenderer {
-    SkPdfNativeDoc* fPdfDoc;
 public:
     SkPdfRenderer() : fPdfDoc(NULL) {}
     virtual ~SkPdfRenderer() {unload();}
 
+    // Render a specific page into the canvas, in a specific rectangle.
     bool renderPage(int page, SkCanvas* canvas, const SkRect& dst) const;
 
     // TODO(edisonn): deprecated, should be removed!
     bool load(const SkString inputFileName);
 
+    // TODO(edisonn): replace it with a SkSmartStream which would know to to efficiently
+    // deal with a HTTP stream.
     bool load(SkStream* stream);
 
+    // Unloads the pdf document.
     void unload();
 
-    bool loaded() const {return fPdfDoc != NULL;}
+    // Returns true if we succesfully loaded a document.
+    bool loaded() const {return fPdfDoc != NULL && pages() > 0;}
 
+    // Returns the number of pages in the loaded pdf.
     int pages() const;
 
+    // Returns the MediaBox of a page. Can be used by client to crate a canvas.
     SkRect MediaBox(int page) const;
 
     // TODO(edisonn): for testing only, probably it should be removed, unless some client wants to
     // let users know how much memory the PDF needs.
     size_t bytesUsed() const;
+
+private:
+    SkPdfNativeDoc* fPdfDoc;
 };
 
+// For testing only, reports stats about rendering, like how many operations failed, or are NYI, ...
 void reportPdfRenderStats();
 
+// Renders a page of a pdf in a bitmap.
 bool SkPDFNativeRenderToBitmap(SkStream* stream,
                                SkBitmap* output,
                                int page = 0,
                                SkPdfContent content = kAll_SkPdfContent,
                                double dpi = 72.0);
 
+// TODO(edisonn): add options to render forms, checkboxes, ...
+// TODO(edisonn): Add API for Forms viewing and editing
+// e.g. SkBitmap getPage(int page);
+//      int formsCount();
+//      SkForm getForm(int formID); // SkForm(SkRect, .. other data)
+// TODO (edisonn): Add intend when loading pdf, for example: for viewing, for parsing content, ...
+
 #endif  // SkPdfRenderer_DEFINED