obs-browser: BrowserSource::Impl::Listener::OnDraw checks if

 browser has not been destroyed to prevent race condition

Author: zavitax

obs-browser/browser-manager-base.cpp

@@ -10,6 +10,7 @@
 #include "browser-render-handler.hpp"
 #include "browser-load-handler.hpp"
 #include "browser-obs-bridge-base.hpp"
+#include "browser-listener.hpp"
 
 BrowserManager::BrowserManager()
 : pimpl(new BrowserManager::Impl())
@@ -35,6 +36,11 @@ int BrowserManager::CreateBrowser(
 	return pimpl->CreateBrowser(browserSettings, browserListener);
 }
 
+bool BrowserManager::IsValidBrowserIdentifier(int browserIdentifier)
+{
+	return pimpl->IsValidBrowserIdentifier(browserIdentifier);
+}
+
 void BrowserManager::DestroyBrowser(int browserIdentifier)
 {
 	pimpl->DestroyBrowser(browserIdentifier);
@@ -128,7 +134,7 @@ int BrowserManager::Impl::CreateBrowser(
 		const BrowserSettings &browserSettings,
 		const std::shared_ptr<BrowserListener> &browserListener)
 {
-	int browserIdentifier = 0;
+	int browserIdentifier = -1;
 	os_event_t *createdEvent;
 	os_event_init(&createdEvent, OS_EVENT_TYPE_AUTO);
 
@@ -167,6 +173,7 @@ int BrowserManager::Impl::CreateBrowser(
 
 		if (browser != nullptr) {
 			browserIdentifier = browser->GetIdentifier();
+			browserListener->SetBrowserIdentifier(browserIdentifier);
 			browserMap[browserIdentifier] = browser;
 		}
 		os_event_signal(createdEvent);
@@ -177,11 +184,17 @@ int BrowserManager::Impl::CreateBrowser(
 	return browserIdentifier;
 }
 
+bool BrowserManager::Impl::IsValidBrowserIdentifier(int browserIdentifier)
+{
+	return browserIdentifier >= 0 && browserMap.count(browserIdentifier) > 0;
+}
+
 void 
 BrowserManager::Impl::DestroyBrowser(int browserIdentifier)
 {
 	if (browserMap.count(browserIdentifier) > 0) {
 		CefRefPtr<CefBrowser> browser = browserMap[browserIdentifier];
+		browserMap.erase(browserIdentifier);
 		os_event_t *closeEvent;
 		os_event_init(&closeEvent, OS_EVENT_TYPE_AUTO);
 		CefPostTask(TID_UI, BrowserTask::newTask([&, browser] 

obs-browser/browser-manager-base.hpp

@@ -33,6 +33,7 @@ class BrowserManager::Impl
 		const BrowserSettings &browserSettings,
 		const std::shared_ptr<BrowserListener> &browserListener);
 
+	bool IsValidBrowserIdentifier(int browserIdentifier);
 	void DestroyBrowser(int browserIdentifier);
 	void TickBrowser(int browserIdentifier);
 

obs-browser/browser-source-listener-base.cpp

@@ -19,13 +19,22 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include "browser-source-base.hpp"
 #include "browser-types.h"
 #include "browser-source-listener-base.hpp"
+#include "browser-manager-base.hpp"
 
 void BrowserSource::Impl::Listener::OnDraw( BrowserSurfaceHandle surfaceHandle,
 		int width, int height)
 {
 	UNUSED_PARAMETER(width);
 	UNUSED_PARAMETER(height);
 
+	// Check if our browser has not been destroyed yet.
+	//
+	// Due to the asynchronous nature of CEF, we can get an OnDraw call after
+	// BrowserManager::Instance()->DestroyBrowser() call has been made.
+	//
+	if (!BrowserManager::Instance()->IsValidBrowserIdentifier(GetBrowserIdentifier()))
+		return;
+
 	if (textureSet.count(surfaceHandle) > 0) {
 		obs_enter_graphics();
 		if (browserSource)
@@ -102,4 +111,4 @@ void BrowserSource::Impl::Listener::DestroySurface(
 		browserSource->activeTexture = nullptr;
 		obs_leave_graphics();
 	}
-}
+}

shared/browser-listener.hpp

@@ -81,4 +81,18 @@ class BrowserListener : public BrowserListenerBase
 	}
 
 	virtual void Invalidated() override {}
-};
+
+private:
+	int m_browserIdentifier = -1;
+
+public:
+	void SetBrowserIdentifier(const int browserIdentifier)
+	{
+		m_browserIdentifier = browserIdentifier;
+	}
+
+	const int GetBrowserIdentifier()
+	{
+		return m_browserIdentifier;
+	}
+};

shared/browser-manager.hpp

@@ -42,6 +42,8 @@ class BrowserManager {
 			const std::shared_ptr<BrowserListener>
 				&browserListener);
 
+	bool IsValidBrowserIdentifier(int browserIdentifier);
+
 	void DestroyBrowser(int browserIdentifier);
 
 	void TickBrowser(int browserIdentifier);