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// Copyright 2025 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef THIRD_PARTY_BLINK_RENDERER_MODULES_XR_XR_SWAP_CHAIN_H_
#define THIRD_PARTY_BLINK_RENDERER_MODULES_XR_XR_SWAP_CHAIN_H_
#include "third_party/blink/renderer/modules/xr/xr_composition_layer.h"
#include "third_party/blink/renderer/platform/heap/garbage_collected.h"
#include "third_party/blink/renderer/platform/heap/member.h"
namespace blink {
// An XRSwapChain manages the creation and lifetime of textures used by an
// XRCompositorLayer. The general lifetime is expected to be:
//
// OnFrameStart() - Called prior to the XRFrame callback for any active layers
// GetCurrentTexture() - Called when a sub image is requested for the layer
// > ProduceTexture() - Called by GetCurrentTexture if a new texture is needed
// OnFrameEnd() - Called prior to the frame submission
// > ResetCurrentTexture() - Called by OnFrameEnd if a new texture is required
// for the next frame.
template <typename Texture>
class XRSwapChain : public GarbageCollected<XRSwapChain<Texture>> {
public:
XRSwapChain() {}
virtual ~XRSwapChain() = default;
Texture* GetCurrentTexture() {
texture_queried_ = true;
if (!current_texture_) {
current_texture_ = ProduceTexture();
}
return current_texture_;
}
virtual void OnFrameStart() { texture_queried_ = false; }
virtual void OnFrameEnd() { ResetCurrentTexture(); }
// Manage the XRCompositorLayer this swap chain is associated with.
virtual void SetLayer(XRCompositionLayer* layer) { layer_ = layer; }
XRCompositionLayer* layer() { return layer_.Get(); }
// Indicates if the texture was queried during the most recent frame.
bool texture_was_queried() const { return texture_queried_; }
virtual void Trace(Visitor* visitor) const {
visitor->Trace(current_texture_);
visitor->Trace(layer_);
}
protected:
// Produces a new Texture for the swap chain. Will not be called again unless
// the current texture is reset.
virtual Texture* ProduceTexture() = 0;
// Resets the cached texture so that next GetCurrentTexture call will trigger
// a ProduceTexture call.
Texture* ResetCurrentTexture() {
Texture* texture = current_texture_.Get();
current_texture_ = nullptr;
return texture;
}
// Return the current texture if one has been produced and not reset.
Texture* current_texture() { return current_texture_; }
private:
Member<Texture> current_texture_;
Member<XRCompositionLayer> layer_;
bool texture_queried_;
};
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_MODULES_XR_XR_SWAP_CHAIN_H_
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