Irrlicht: expire unused hardware buffers (#17059)

Author: sfan5

irr/src/CNullDriver.cpp

@@ -984,11 +984,17 @@ void CNullDriver::registerHardwareBuffer(SHWBufferLink *HWBuffer)
 
 void CNullDriver::expireHardwareBuffers()
 {
+	// 10 - 30s at usual framerates
+	constexpr u16 DELETE_AFTER_UNUSED_FRAMES = 60 * 25;
+
 	for (size_t i = 0; i < HWBufferList.size(); ) {
 		auto *link = HWBufferList[i];
 
+		bool del = link->UnusedCounter++ >= DELETE_AFTER_UNUSED_FRAMES ||
+			!link->Buffer || link->Buffer->getReferenceCount() == 1;
+
 		// deleting can reorder, so don't advance in list
-		if (!link->Buffer || link->Buffer->getReferenceCount() == 1)
+		if (del)
 			deleteHardwareBuffer(link);
 		else
 			i++;

irr/src/CNullDriver.h

@@ -305,12 +305,13 @@ class CNullDriver : public IVideoDriver, public IGPUProgrammingServices
 		const scene::HWBuffer *Buffer;
 		size_t ListPosition = static_cast<size_t>(-1);
 		u32 ChangedID = 0;
+		u16 UnusedCounter = 0;
 	};
 
 	//! Gets hardware buffer link from a buffer (may create or update buffer)
 	virtual SHWBufferLink *getBufferLink(const scene::HWBuffer *buf);
 
-	//! updates hardware buffer if needed  (only some drivers can)
+	//! updates hardware buffer if needed
 	virtual bool updateHardwareBuffer(SHWBufferLink *HWBuffer) { return false; }
 
 	//! Delete hardware buffer

irr/src/COpenGLDriver.cpp

@@ -374,6 +374,7 @@ bool COpenGLDriver::updateHardwareBuffer(SHWBufferLink *_link)
 
 	auto *link = IRR_DOWN_CAST<SHWBufferLink_opengl *>(_link);
 	auto *buf = link->Buffer;
+	link->UnusedCounter = 0;
 	if (link->vbo_ID && link->ChangedID == buf->getChangedID())
 		return true;
 

irr/src/OpenGL/Driver.cpp

@@ -537,6 +537,7 @@ bool COpenGL3DriverBase::updateHardwareBuffer(SHWBufferLink *HWBuffer)
 
 	auto *b = static_cast<SHWBufferLink_opengl *>(HWBuffer);
 
+	b->UnusedCounter = 0;
 	assert(b->Buffer);
 	if (b->ChangedID != b->Buffer->getChangedID() || !b->Vbo.exists()) {
 		if (!_updateHardwareBuffer(b))