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

experimental/PdfViewer/SkPdfRenderer.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkPdfRenderer.h"
 
 #include "SkBitmapDevice.h"
@@ skipping 3044 matching lines @@
 #else
     SkPoint skiaSpace[4] = {SkPoint::Make(z, h),
                             SkPoint::Make(w, h),
                             SkPoint::Make(w, z),
                             SkPoint::Make(z, z)};
 #endif
 
     SkAssertResult(pdfContext.fOriginalMatrix.setPolyToPoly(pdfSpace, skiaSpace, 4));
     SkTraceMatrix(pdfContext.fOriginalMatrix, "Original matrix");
 
+    pdfContext.fOriginalMatrix.postConcat(canvas->getTotalMatrix());
+
     pdfContext.fGraphicsState.fCTM = pdfContext.fOriginalMatrix;
     pdfContext.fGraphicsState.fContentStreamMatrix = pdfContext.fOriginalMatrix;
     pdfContext.fGraphicsState.fMatrixTm = pdfContext.fGraphicsState.fCTM;
     pdfContext.fGraphicsState.fMatrixTlm = pdfContext.fGraphicsState.fCTM;
 
 #ifndef PDF_DEBUG_NO_PAGE_CLIPING
     canvas->clipRect(dst, SkRegion::kIntersect_Op, true);
 #endif
 
-    canvas->setMatrix(pdfContext.fOriginalMatrix);
+    canvas->concat(pdfContext.fOriginalMatrix);
 
     doPage(&pdfContext, canvas, fPdfDoc->page(page));
 
           // TODO(edisonn:) erase with white before draw? Right now the caller is responsible.
 //        SkPaint paint;
 //        paint.setColor(SK_ColorWHITE);
 //        canvas->drawRect(rect, paint);
 
 
     canvas->flush();
@@ skipping 63 matching lines @@
 
     rect = SkRect::MakeWH(width, height);
 
     setup_bitmap(output, (int)SkScalarToDouble(width), (int)SkScalarToDouble(height));
 
     SkAutoTUnref<SkBaseDevice> device(SkNEW_ARGS(SkBitmapDevice, (*output)));
     SkCanvas canvas(device);
 
     return renderer.renderPage(page, &canvas, rect);
 }