Bug 1813148 - Don't return already_AddRefed in nsPresContext::GetRootWidget. r=dholbert

Let the caller addref it if needed.

I wrote this because I wanted to make some code dealing with it
thread-safe, but I ended up writing a less sketchy solution. However I
still think this is worth it.

It seems this only returns an already_AddRefed because before it used to
be an XPCOM-ish thing where the widget was returned as an out-param.

For now it doesn't change behavior but there are some callers that would
benefit from having less addref/release calls if they only need to read
simple stuff from the widget.

Differential Revision: https://phabricator.services.mozilla.com/D168141

Author: emilio

dom/events/TextComposition.h

@@ -81,7 +81,10 @@ class TextComposition final {
   TextRangeArray* GetRanges() const { return mRanges; }
   // Returns the widget which is proper to call NotifyIME().
   already_AddRefed<nsIWidget> GetWidget() const {
-    return mPresContext ? mPresContext->GetRootWidget() : nullptr;
+    if (!mPresContext) {
+      return nullptr;
+    }
+    return do_AddRef(mPresContext->GetRootWidget());
   }
   // Returns the tab parent which has this composition in its remote process.
   BrowserParent* GetBrowserParent() const { return mBrowserParent; }

dom/ipc/BrowserParent.cpp

@@ -356,7 +356,7 @@ already_AddRefed<nsPIDOMWindowOuter> BrowserParent::GetParentWindowOuter() {
 already_AddRefed<nsIWidget> BrowserParent::GetTopLevelWidget() {
   if (RefPtr<Element> element = mFrameElement) {
     if (PresShell* presShell = element->OwnerDoc()->GetPresShell()) {
-      return presShell->GetViewManager()->GetRootWidget();
+      return do_AddRef(presShell->GetViewManager()->GetRootWidget());
     }
   }
   return nullptr;

layout/base/nsPresContext.cpp

@@ -1167,13 +1167,12 @@ nsIWidget* nsPresContext::GetNearestWidget(nsPoint* aOffset) {
   return rootView->GetNearestWidget(aOffset);
 }
 
-already_AddRefed<nsIWidget> nsPresContext::GetRootWidget() const {
+nsIWidget* nsPresContext::GetRootWidget() const {
   NS_ENSURE_TRUE(mPresShell, nullptr);
   nsViewManager* vm = mPresShell->GetViewManager();
   if (!vm) {
     return nullptr;
   }
-
   return vm->GetRootWidget();
 }
 

layout/base/nsPresContext.h

@@ -238,13 +238,13 @@ class nsPresContext : public nsISupports, public mozilla::SupportsWeakPtr {
   /**
    * Returns the root widget for this.
    */
-  already_AddRefed<nsIWidget> GetRootWidget() const;
+  nsIWidget* GetRootWidget() const;
 
   /**
    * Returns the widget which may have native focus and handles text input
    * like keyboard input, IME, etc.
    */
-  already_AddRefed<nsIWidget> GetTextInputHandlingWidget() const {
+  nsIWidget* GetTextInputHandlingWidget() const {
     // Currently, root widget for each PresContext handles text input.
     return GetRootWidget();
   }

view/nsViewManager.cpp

@@ -895,16 +895,17 @@ void nsViewManager::DecrementDisableRefreshCount() {
   NS_ASSERTION(mRefreshDisableCount >= 0, "Invalid refresh disable count!");
 }
 
-already_AddRefed<nsIWidget> nsViewManager::GetRootWidget() {
-  nsCOMPtr<nsIWidget> rootWidget;
-  if (mRootView) {
-    if (mRootView->HasWidget()) {
-      rootWidget = mRootView->GetWidget();
-    } else if (mRootView->GetParent()) {
-      rootWidget = mRootView->GetParent()->GetViewManager()->GetRootWidget();
-    }
+nsIWidget* nsViewManager::GetRootWidget() const {
+  if (!mRootView) {
+    return nullptr;
+  }
+  if (mRootView->HasWidget()) {
+    return mRootView->GetWidget();
+  }
+  if (mRootView->GetParent()) {
+    return mRootView->GetParent()->GetViewManager()->GetRootWidget();
   }
-  return rootWidget.forget();
+  return nullptr;
 }
 
 LayoutDeviceIntRect nsViewManager::ViewToWidget(nsView* aView,

view/nsViewManager.h

@@ -282,7 +282,7 @@ class nsViewManager final {
    * Retrieve the widget at the root of the nearest enclosing
    * view manager whose root view has a widget.
    */
-  already_AddRefed<nsIWidget> GetRootWidget();
+  nsIWidget* GetRootWidget() const;
 
   /**
    * Indicate whether the viewmanager is currently painting