Use strict types in FPDF API, try #3

Rather than messing with actual inheritence, add type-checking wrappers
and just blatantly cast to incomplete types.  Along the way, this points
out places where we would downcast without checking, which I fix.

Change-Id: Ieb303eb46ad8522dfe082454f1f10f247ffd52d5
Reviewed-on: https://pdfium-review.googlesource.com/32030
Reviewed-by: dsinclair <dsinclair@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>

1 files changed, 35 insertions, 0 deletions

diff --git a/fpdfsdk/cpdf_annotcontext.cpp b/fpdfsdk/cpdf_annotcontext.cpp
new file mode 100644
index 0000000000..d76d5d2f8c
--- /dev/null
+++ b/fpdfsdk/cpdf_annotcontext.cpp
@@ -0,0 +1,35 @@
+// Copyright 2018 PDFium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
+
+#include "fpdfsdk/cpdf_annotcontext.h"
+
+#include "core/fpdfapi/page/cpdf_form.h"
+#include "core/fpdfapi/page/cpdf_page.h"
+#include "core/fpdfapi/parser/cpdf_dictionary.h"
+#include "core/fpdfapi/parser/cpdf_stream.h"
+#include "third_party/base/ptr_util.h"
+
+CPDF_AnnotContext::CPDF_AnnotContext(CPDF_Dictionary* pAnnotDict,
+                                     CPDF_Page* pPage,
+                                     CPDF_Stream* pStream)
+    : m_pAnnotDict(pAnnotDict), m_pPage(pPage) {
+  SetForm(pStream);
+}
+
+CPDF_AnnotContext::~CPDF_AnnotContext() = default;
+
+void CPDF_AnnotContext::SetForm(CPDF_Stream* pStream) {
+  if (!pStream)
+    return;
+
+  // Reset the annotation matrix to be the identity matrix, since the
+  // appearance stream already takes matrix into account.
+  pStream->GetDict()->SetMatrixFor("Matrix", CFX_Matrix());
+
+  m_pAnnotForm = pdfium::MakeUnique<CPDF_Form>(
+      m_pPage->m_pDocument.Get(), m_pPage->m_pResources.Get(), pStream);
+  m_pAnnotForm->ParseContent();
+}