We can't execute the application now because the swap chain image needs to be ready to be presented by the GPU before calling present(). To make this frame buffer ready to be presented, we have to use a pipeline barrier to synchronize resource like image between the different stages of a GPU pipeline.

A pipeline barrier is a GPU synchronization primitive that guarantees that any writes performed by those earlier stages are made visible (and available) to reads or writes in the later stages.

A pipeline barrier is created on the GPU with the help of a CommandList and a command list is allocated by a CommandAllocator.

The command list will also be used to record pipeline and drawing commands for execution by the GPU.

Since we can render multiple frames in flight, we need one allocator and one list per frame:

struct FrameData {
    std::shared_ptr<vireo::Fence>            inFlightFence;
    std::shared_ptr<vireo::CommandAllocator> commandAllocator;
    std::shared_ptr<vireo::CommandList>      commandList;
};

Add the creation code after the fence creation :

for (auto& frameData : framesData) {
    frameData.inFlightFence = vireo->createFence(true);
    frameData.commandAllocator = vireo->createCommandAllocator(vireo::CommandType::GRAPHIC);
    frameData.commandList = frameData.commandAllocator->createCommandList();
}

Command lists need to be :

Reset before use (via the command allocator in this tutorial)
Submitted to the GPU with a submission queue

We will do that between acquire() and present():

...
frameData.commandAllocator->reset();
 
// commands will be recorded and submitted here
 
graphicQueue->submit(
    frameData.inFlightFence,
    swapChain,
    {frameData.commandList});
...

Recording commands in the command list is done in a recording session. A session starts with vireo::CommandList::begin and ends with vireo::CommandList::end, between reset() and submit() :

...
frameData.commandList->begin();
 
// commands will be recorded and submitted here
 
frameData.commandList->end();
...

We can finally add the pipeline barriers for the current swap chain frame buffer between begin() and end():

frameData.commandList->barrier(
    swapChain,
    vireo::ResourceState::UNDEFINED,
    vireo::ResourceState::RENDER_TARGET_COLOR);
 
// commands will be recorded and submitted here
 
frameData.commandList->barrier(
    swapChain,
    vireo::ResourceState::RENDER_TARGET_COLOR,
    vireo::ResourceState::PRESENT);

The application can be started to display a black window (since we never write data into the frame buffer):

Next : Render pass

Related manual page : Command Lists