Add CPDSDK_Annot::AsBAAnnot() checked downcast method

XFA introduces some additional subclasses, so it doesn't hurt
to be sure in all cases before making a static cast.

Change-Id: I7447ca58be0b57201b39ba40a3fc5f47505cee58
Reviewed-on: https://pdfium-review.googlesource.com/39013
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>

6 files changed, 22 insertions, 6 deletions

diff --git a/fpdfsdk/cpdfsdk_annot.cpp b/fpdfsdk/cpdfsdk_annot.cpp
index cfd87b3255..75967a301f 100644
--- a/fpdfsdk/cpdfsdk_annot.cpp
+++ b/fpdfsdk/cpdfsdk_annot.cpp
@@ -27,6 +27,10 @@ CPDFSDK_Annot::CPDFSDK_Annot(CPDFSDK_PageView* pPageView)
 
 CPDFSDK_Annot::~CPDFSDK_Annot() {}
 
+CPDFSDK_BAAnnot* CPDFSDK_Annot::AsBAAnnot() {
+  return nullptr;
+}
+
 #ifdef PDF_ENABLE_XFA
 
 bool CPDFSDK_Annot::IsXFAField() {
diff --git a/fpdfsdk/cpdfsdk_annot.h b/fpdfsdk/cpdfsdk_annot.h
index 459c6d0233..708a223a50 100644
--- a/fpdfsdk/cpdfsdk_annot.h
+++ b/fpdfsdk/cpdfsdk_annot.h
@@ -20,6 +20,7 @@ class CFX_Matrix;
 class CFX_RenderDevice;
 class CPDF_Page;
 class CPDF_RenderOptions;
+class CPDFSDK_BAAnnot;
 class CPDFSDK_PageView;
 
 #ifdef PDF_ENABLE_XFA
@@ -31,6 +32,8 @@ class CPDFSDK_Annot : public Observable<CPDFSDK_Annot> {
   explicit CPDFSDK_Annot(CPDFSDK_PageView* pPageView);
   virtual ~CPDFSDK_Annot();
 
+  virtual CPDFSDK_BAAnnot* AsBAAnnot();
+
 #ifdef PDF_ENABLE_XFA
   virtual bool IsXFAField();
   virtual CXFA_FFWidget* GetXFAWidget() const;
@@ -57,4 +60,8 @@ class CPDFSDK_Annot : public Observable<CPDFSDK_Annot> {
   UnownedPtr<CPDFSDK_PageView> const m_pPageView;
 };
 
+inline CPDFSDK_BAAnnot* ToBAAnnot(CPDFSDK_Annot* pAnnot) {
+  return pAnnot ? pAnnot->AsBAAnnot() : nullptr;
+}
+
 #endif  // FPDFSDK_CPDFSDK_ANNOT_H_
diff --git a/fpdfsdk/cpdfsdk_baannot.cpp b/fpdfsdk/cpdfsdk_baannot.cpp
index f9d1f620ac..6f5e3f95a6 100644
--- a/fpdfsdk/cpdfsdk_baannot.cpp
+++ b/fpdfsdk/cpdfsdk_baannot.cpp
@@ -26,6 +26,10 @@ CPDFSDK_BAAnnot::CPDFSDK_BAAnnot(CPDF_Annot* pAnnot,
 
 CPDFSDK_BAAnnot::~CPDFSDK_BAAnnot() {}
 
+CPDFSDK_BAAnnot* CPDFSDK_BAAnnot::AsBAAnnot() {
+  return this;
+}
+
 CPDF_Annot* CPDFSDK_BAAnnot::GetPDFAnnot() const {
   return m_pAnnot.Get();
 }
diff --git a/fpdfsdk/cpdfsdk_baannot.h b/fpdfsdk/cpdfsdk_baannot.h
index f2fdd30b64..778f75735f 100644
--- a/fpdfsdk/cpdfsdk_baannot.h
+++ b/fpdfsdk/cpdfsdk_baannot.h
@@ -28,6 +28,7 @@ class CPDFSDK_BAAnnot : public CPDFSDK_Annot {
   ~CPDFSDK_BAAnnot() override;
 
   // CPDFSDK_Annot
+  CPDFSDK_BAAnnot* AsBAAnnot() override;
   CPDF_Annot::Subtype GetAnnotSubtype() const override;
   void SetRect(const CFX_FloatRect& rect) override;
   CFX_FloatRect GetRect() const override;
diff --git a/fpdfsdk/cpdfsdk_baannothandler.cpp b/fpdfsdk/cpdfsdk_baannothandler.cpp
index ab46a9683c..a5969c98a2 100644
--- a/fpdfsdk/cpdfsdk_baannothandler.cpp
+++ b/fpdfsdk/cpdfsdk_baannothandler.cpp
@@ -72,15 +72,15 @@ void CPDFSDK_BAAnnotHandler::OnDraw(CPDFSDK_PageView* pPageView,
     return;
 #endif  // PDF_ENABLE_XFA
   if (bDrawAnnots && pAnnot->GetAnnotSubtype() == CPDF_Annot::Subtype::POPUP) {
-    static_cast<CPDFSDK_BAAnnot*>(pAnnot)->DrawAppearance(
-        pDevice, *pUser2Device, CPDF_Annot::Normal, nullptr);
+    pAnnot->AsBAAnnot()->DrawAppearance(pDevice, *pUser2Device,
+                                        CPDF_Annot::Normal, nullptr);
   }
 }
 
 void CPDFSDK_BAAnnotHandler::OnMouseEnter(CPDFSDK_PageView* pPageView,
                                           CPDFSDK_Annot::ObservedPtr* pAnnot,
                                           uint32_t nFlag) {
-  CPDFSDK_BAAnnot* pBAAnnot = static_cast<CPDFSDK_BAAnnot*>(pAnnot->Get());
+  CPDFSDK_BAAnnot* pBAAnnot = (*pAnnot)->AsBAAnnot();
   pBAAnnot->SetOpenState(true);
   UpdateAnnotRects(pPageView, pBAAnnot);
 }
@@ -88,7 +88,7 @@ void CPDFSDK_BAAnnotHandler::OnMouseEnter(CPDFSDK_PageView* pPageView,
 void CPDFSDK_BAAnnotHandler::OnMouseExit(CPDFSDK_PageView* pPageView,
                                          CPDFSDK_Annot::ObservedPtr* pAnnot,
                                          uint32_t nFlag) {
-  CPDFSDK_BAAnnot* pBAAnnot = static_cast<CPDFSDK_BAAnnot*>(pAnnot->Get());
+  CPDFSDK_BAAnnot* pBAAnnot = (*pAnnot)->AsBAAnnot();
   pBAAnnot->SetOpenState(false);
   UpdateAnnotRects(pPageView, pBAAnnot);
 }
diff --git a/fpdfsdk/cpdfsdk_widgethandler.cpp b/fpdfsdk/cpdfsdk_widgethandler.cpp
index 22f5d3933a..7cfe74f413 100644
--- a/fpdfsdk/cpdfsdk_widgethandler.cpp
+++ b/fpdfsdk/cpdfsdk_widgethandler.cpp
@@ -92,8 +92,8 @@ void CPDFSDK_WidgetHandler::OnDraw(CPDFSDK_PageView* pPageView,
                                    CFX_Matrix* pUser2Device,
                                    bool bDrawAnnots) {
   if (pAnnot->IsSignatureWidget()) {
-    static_cast<CPDFSDK_BAAnnot*>(pAnnot)->DrawAppearance(
-        pDevice, *pUser2Device, CPDF_Annot::Normal, nullptr);
+    pAnnot->AsBAAnnot()->DrawAppearance(pDevice, *pUser2Device,
+                                        CPDF_Annot::Normal, nullptr);
   } else {
     if (m_pFormFiller)
       m_pFormFiller->OnDraw(pPageView, pAnnot, pDevice, pUser2Device);