[Native] WindowsDX12 fixes #2 by arosolino · Pull Request #9031

[Native] WindowsDX12 fixes #2 by arosolino · Pull Request #9031 · MonoGame/MonoGame

@tomspilman There is a major bug where a buffer remains on the free list when it doesn't match the exact size.

Not being removed from the free list on this line:

I supplied a fix for now but I noticed that Vulkan takes a different approach to the the free, pending, discarded by using a linked list. Since we are trying to accomplish the same goal on both of these platforms which approach should be taken here?

DX12: MGDX_BufferDiscard

	static MGG_Buffer* MGDX_BufferDiscard(MGG_GraphicsDevice* device, MGG_Buffer* buffer)
	{
	// Get the info we need to find/allocate a new buffer.
	auto dataSize = buffer->dataSize;
	auto type = buffer->type;

	// Add it to the discard list.
	device->discarded.push_back(buffer);

	// Search for the best fit from the free list.
	MGG_Buffer* best = nullptr;
	for (int i=0; i < device->free.size(); i++)
	{
	auto curr = device->free[i];

	if (curr->type != type)
	continue;
	auto currSize = curr->actualSize;

	if (currSize < dataSize)
	continue;

	if (best == nullptr \|\| best->actualSize > currSize)
	{
	best = curr;

	if (currSize == dataSize)
	{
	device->free[i] = device->free.back();
	device->free.pop_back();
	break;
	}
	}
	}

	// We didn't find a match, so allocate a new one.
	if (best == nullptr)
	best = MGG_Buffer_Create(device, type, dataSize);

	best->dataSize = dataSize;

	return best;
	}

Vulkan: MGVK_BufferDiscard

	static MGG_Buffer* MGVK_BufferDiscard(MGG_GraphicsDevice* device, MGG_Buffer* buffer)
	{
	// Get the info we need to find/allocate a new buffer.
	auto dataSize = buffer->dataSize;
	auto type = buffer->type;

	// Discard the current buffer.
	assert(buffer->next == nullptr);
	buffer->next = device->discarded;
	device->discarded = buffer;
	buffer = nullptr;

	// Search for the best fit from the free list.
	MGG_Buffer** curr = &device->free;
	MGG_Buffer** best = nullptr;
	while (*curr != nullptr)
	{
	if ((*curr)->type == type)
	{
	auto currSize = (*curr)->actualSize;

	if (currSize >= dataSize)
	{
	if (best == nullptr \|\| (*best)->actualSize > currSize)
	{
	best = curr;
	if (currSize == dataSize)
	break;
	}
	}
	}

	curr = &(*curr)->next;
	}

	// Did we find a match?
	if (best != nullptr)
	{
	buffer = *best;
	*best = buffer->next;
	buffer->next = nullptr;
	buffer->dataSize = dataSize;
	//buffer->dirtyMin = 0;
	//buffer->dirtyMax = 0;
	return buffer;
	}

	// We didn't find a match, so allocate a new one.
	buffer = MGG_Buffer_Create(device, type, dataSize);

	return buffer;
	}