Setting focus on a widget may destroy the widget

When a widget has focus set, this can trigger an Invalidation call which
can trigger a page and annotation reload. This reload can destroy the
current widget we're handling.

This CL adds ObservedPtrs as needed so we can make sure the widgets are
still alive after we've done the Invalidation.

Bug: chromium:765921
Change-Id: I51cd24aa1ebd96abe9478efef5130a4e568dac1a
Reviewed-on: https://pdfium-review.googlesource.com/14290
Commit-Queue: dsinclair <dsinclair@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>

3 files changed, 36 insertions, 11 deletions

diff --git a/fpdfsdk/pwl/cpwl_caret.cpp b/fpdfsdk/pwl/cpwl_caret.cpp
index b1040bc2e3..99d2e2ece7 100644
--- a/fpdfsdk/pwl/cpwl_caret.cpp
+++ b/fpdfsdk/pwl/cpwl_caret.cpp
@@ -59,6 +59,8 @@ void CPWL_Caret::TimerProc() {
   } else {
     m_bFlash = !m_bFlash;
     InvalidateRect(nullptr);
+    // Note, |this| may no longer be viable at this point. If more work needs
+    // to be done, add an observer.
   }
 }
 
@@ -77,15 +79,24 @@ void CPWL_Caret::SetCaret(bool bVisible,
         m_ptFoot = ptFoot;
         m_bFlash = true;
         Move(m_rcInvalid, false, true);
+        // Note, |this| may no longer be viable at this point. If more work
+        // needs to be done, add an observer.
       }
     } else {
       m_ptHead = ptHead;
       m_ptFoot = ptFoot;
       EndTimer();
       BeginTimer(PWL_CARET_FLASHINTERVAL);
+
+      ObservedPtr observer(this);
       CPWL_Wnd::SetVisible(true);
+      if (!observer)
+        return;
+
       m_bFlash = true;
       Move(m_rcInvalid, false, true);
+      // Note, |this| may no longer be viable at this point. If more work needs
+      // to be done, add an observer.
     }
   } else {
     m_ptHead = CFX_PointF();
@@ -94,6 +105,8 @@ void CPWL_Caret::SetCaret(bool bVisible,
     if (IsVisible()) {
       EndTimer();
       CPWL_Wnd::SetVisible(false);
+      // Note, |this| may no longer be viable at this point. If more work needs
+      // to be done, add an observer.
     }
   }
 }
@@ -111,4 +124,6 @@ void CPWL_Caret::InvalidateRect(CFX_FloatRect* pRect) {
   } else {
     CPWL_Wnd::InvalidateRect(pRect);
   }
+  // Note, |this| may no longer be viable at this point. If more work needs
+  // to be done, add an observer.
 }
diff --git a/fpdfsdk/pwl/cpwl_edit.cpp b/fpdfsdk/pwl/cpwl_edit.cpp
index c71dbe4be0..0b74a1896e 100644
--- a/fpdfsdk/pwl/cpwl_edit.cpp
+++ b/fpdfsdk/pwl/cpwl_edit.cpp
@@ -331,16 +331,24 @@ bool CPWL_Edit::OnRButtonUp(const CFX_PointF& point, uint32_t nFlag) {
 }
 
 void CPWL_Edit::OnSetFocus() {
+  ObservedPtr observed_ptr(this);
   SetEditCaret(true);
+  if (!observed_ptr)
+    return;
+
   if (!IsReadOnly()) {
-    if (CPWL_Wnd::FocusHandlerIface* pFocusHandler = GetFocusHandler())
+    if (CPWL_Wnd::FocusHandlerIface* pFocusHandler = GetFocusHandler()) {
       pFocusHandler->OnSetFocus(this);
+      if (!observed_ptr)
+        return;
+    }
   }
   m_bFocus = true;
 }
 
 void CPWL_Edit::OnKillFocus() {
-  ObservedPtr observed_ptr = ObservedPtr(this);
+  ObservedPtr observed_ptr(this);
+
   CPWL_ScrollBar* pScroll = GetVScrollBar();
   if (pScroll && pScroll->IsVisible()) {
     pScroll->SetVisible(false);
diff --git a/fpdfsdk/pwl/cpwl_wnd.cpp b/fpdfsdk/pwl/cpwl_wnd.cpp
index 1c1512e296..4e4abd2017 100644
--- a/fpdfsdk/pwl/cpwl_wnd.cpp
+++ b/fpdfsdk/pwl/cpwl_wnd.cpp
@@ -86,19 +86,21 @@ class CPWL_MsgControl : public CFX_Observable<CPWL_MsgControl> {
 
   void SetFocus(CPWL_Wnd* pWnd) {
     m_aKeyboardPath.clear();
-    if (pWnd) {
-      m_pMainKeyboardWnd = pWnd;
-      CPWL_Wnd* pParent = pWnd;
-      while (pParent) {
-        m_aKeyboardPath.push_back(pParent);
-        pParent = pParent->GetParentWindow();
-      }
-      pWnd->OnSetFocus();
+    if (!pWnd)
+      return;
+
+    m_pMainKeyboardWnd = pWnd;
+    CPWL_Wnd* pParent = pWnd;
+    while (pParent) {
+      m_aKeyboardPath.push_back(pParent);
+      pParent = pParent->GetParentWindow();
     }
+    // Note, pWnd may get destroyed in the OnSetFocus call.
+    pWnd->OnSetFocus();
   }
 
   void KillFocus() {
-    ObservedPtr observed_ptr = ObservedPtr(this);
+    ObservedPtr observed_ptr(this);
     if (!m_aKeyboardPath.empty())
       if (CPWL_Wnd* pWnd = m_aKeyboardPath[0])
         pWnd->OnKillFocus();