From: Mikko Rasa <tdb@tdb.fi>
Date: Wed, 1 Dec 2021 07:53:10 +0000 (+0200)
Subject: Support transfers with no staged data
X-Git-Url: http://git.tdb.fi/?a=commitdiff_plain;h=5c35768c310847df816d216eecf8fa2e93f5f8b8;p=libs%2Fgl.git

Support transfers with no staged data

This can be used to transfer data within VRAM, such as for mipmap
generation.
---

diff --git a/source/backends/vulkan/transferqueue.cpp b/source/backends/vulkan/transferqueue.cpp
index 87afc3c0..8040f245 100644
--- a/source/backends/vulkan/transferqueue.cpp
+++ b/source/backends/vulkan/transferqueue.cpp
@@ -23,18 +23,21 @@ TransferQueue::PendingTransfer &TransferQueue::prepare_transfer(void *object, bo
 	PendingTransfer &transfer = *transfers.emplace(j);
 	transfer.order = order;
 
-	auto i = find_if(buffers, [size](const StagingBuffer &b){ return b.used+size<=b.size; });
-	if(i==buffers.end())
+	if(size)
 	{
-		buffers.emplace_back(device, max(default_buffer_size, size));
-		i = prev(buffers.end());
-	}
+		auto i = find_if(buffers, [size](const StagingBuffer &b){ return b.used+size<=b.size; });
+		if(i==buffers.end())
+		{
+			buffers.emplace_back(device, max(default_buffer_size, size));
+			i = prev(buffers.end());
+		}
 
-	transfer.buffer_index = distance(buffers.begin(), i);
-	transfer.offset = i->used;
-	transfer.size = size;
+		transfer.buffer_index = distance(buffers.begin(), i);
+		transfer.offset = i->used;
+		transfer.size = size;
 
-	i->used += size;
+		i->used += size;
+	}
 
 	order += ordered;
 
@@ -56,7 +59,7 @@ void TransferQueue::dispatch_transfers(VkCommandBuffer command_buffer)
 
 		for(; i!=j; ++i)
 		{
-			VkBuffer buffer = buffers[i->buffer_index].buffer;
+			VkBuffer buffer = (i->buffer_index>=0 ? buffers[i->buffer_index].buffer : 0);
 			i->transfer(command_buffer, buffer, i->offset);
 		}
 	}
diff --git a/source/backends/vulkan/transferqueue.h b/source/backends/vulkan/transferqueue.h
index b8719d62..b11b4503 100644
--- a/source/backends/vulkan/transferqueue.h
+++ b/source/backends/vulkan/transferqueue.h
@@ -31,7 +31,7 @@ private:
 	struct PendingTransfer
 	{
 		unsigned order = 0;
-		unsigned buffer_index = 0;
+		int buffer_index = -1;
 		std::size_t offset = 0;
 		std::size_t size = 0;
 		std::function<void()> synchronize;
@@ -63,7 +63,7 @@ void *TransferQueue::prepare_transfer(void *object, bool ordered, std::size_t si
 	PendingTransfer &pt = prepare_transfer(object, ordered, size);
 	pt.synchronize = std::forward<S>(synchronize);
 	pt.transfer = std::forward<T>(transfer);
-	return static_cast<char *>(buffers[pt.buffer_index].mapped_address)+pt.offset;
+	return (pt.buffer_index<0 ? 0 : static_cast<char *>(buffers[pt.buffer_index].mapped_address)+pt.offset);
 }
 
 } // namespace GL