Swap chains, part 1 (#87)

Adds the swap chain interfaces to the API without changing the behavior
of anything else. This includes the C APIs for applications to provide
swap chain implementations. Also adds stub implementations on every
backend.

src/backend/null/NullBackend.cpp

@@ -87,6 +87,9 @@ namespace null {
 
         return module;
     }
+    SwapChainBase* Device::CreateSwapChain(SwapChainBuilder* builder) {
+        return new SwapChain(builder);
+    }
     TextureBase* Device::CreateTexture(TextureBuilder* builder) {
         return new Texture(builder);
     }
@@ -222,5 +225,19 @@ namespace null {
     void Texture::TransitionUsageImpl(nxt::TextureUsageBit, nxt::TextureUsageBit) {
     }
 
+    // SwapChain
+
+    SwapChain::SwapChain(SwapChainBuilder* builder)
+        : SwapChainBase(builder) {
+        const auto& im = GetImplementation();
+        im.Init(im.userData, nullptr);
+    }
+
+    SwapChain::~SwapChain() {
+    }
+
+    TextureBase* SwapChain::GetNextTextureImpl(TextureBuilder* builder) {
+        return GetDevice()->CreateTexture(builder);
+    }
 }
 }

src/backend/null/NullBackend.h

@@ -32,6 +32,7 @@
 #include "backend/RenderPipeline.h"
 #include "backend/Sampler.h"
 #include "backend/ShaderModule.h"
+#include "backend/SwapChain.h"
 #include "backend/Texture.h"
 #include "backend/ToBackend.h"
 
@@ -54,6 +55,7 @@ namespace null {
     using RenderPipeline = RenderPipelineBase;
     using Sampler = SamplerBase;
     using ShaderModule = ShaderModuleBase;
+    class SwapChain;
     class Texture;
     using TextureView = TextureViewBase;
 
@@ -74,6 +76,7 @@ namespace null {
         using RenderPipelineType = RenderPipeline;
         using SamplerType = Sampler;
         using ShaderModuleType = ShaderModule;
+        using SwapChainType = SwapChain;
         using TextureType = Texture;
         using TextureViewType = TextureView;
     };
@@ -108,6 +111,7 @@ namespace null {
             RenderPipelineBase* CreateRenderPipeline(RenderPipelineBuilder* builder) override;
             SamplerBase* CreateSampler(SamplerBuilder* builder) override;
             ShaderModuleBase* CreateShaderModule(ShaderModuleBuilder* builder) override;
+            SwapChainBase* CreateSwapChain(SwapChainBuilder* builder) override;
             TextureBase* CreateTexture(TextureBuilder* builder) override;
             TextureViewBase* CreateTextureView(TextureViewBuilder* builder) override;
 
@@ -158,13 +162,22 @@ namespace null {
 
     class Texture : public TextureBase {
         public:
-            Texture(TextureBuilder* buidler);
+            Texture(TextureBuilder* builder);
             ~Texture();
 
         private:
             void TransitionUsageImpl(nxt::TextureUsageBit currentUsage, nxt::TextureUsageBit targetUsage) override;
     };
 
+    class SwapChain : public SwapChainBase {
+        public:
+            SwapChain(SwapChainBuilder* builder);
+            ~SwapChain();
+
+        protected:
+            TextureBase* GetNextTextureImpl(TextureBuilder* builder) override;
+    };
+
 }
 }