From ba49a1e47a3c071cdc72bb548cae84c5f40ac7d7 Mon Sep 17 00:00:00 2001
From: Patrick Wuttke <mewin@mewin.de>
Date: Fri, 13 Sep 2024 09:02:18 +0200
Subject: [PATCH] A triangle.

---
 private/sdl_gpu_test/main.cpp      | 25 ++++++++++++++++++++++---
 private/sdl_gpu_test/sdlpp/gpu.hpp | 24 ++++++++++++++++++++++++
 2 files changed, 46 insertions(+), 3 deletions(-)

diff --git a/private/sdl_gpu_test/main.cpp b/private/sdl_gpu_test/main.cpp
index ef4366d..185bfae 100644
--- a/private/sdl_gpu_test/main.cpp
+++ b/private/sdl_gpu_test/main.cpp
@@ -14,18 +14,27 @@ namespace
 const char* const VERTEX_SOURCE = R"(
 #version 460
 
+const vec2 vertices[3] = vec2[3](
+    vec2(-0.5, 0.5),
+    vec2( 0.5, 0.5),
+    vec2( 0.0, -0.5)
+);
+
 void main()
 {
-
+    gl_Position = vec4(vertices[gl_VertexIndex], 0.0, 1.0);
 }
 )";
 
 const char* const FRAGMENT_SOURCE = R"(
 #version 460
 
+layout(location = 0)
+out vec4 o_color;
+
 void main()
 {
-
+    o_color = vec4(0.0, 1.0, 0.0, 1.0);
 }
 )";
 }
@@ -82,10 +91,18 @@ int main(int, char**)
     });
 
     // create graphics pipeline
+    std::array colorTargetsDescs = {
+        sdlpp::GPUColorTargetDescription{
+            .format = gpuDevice.getSwapchainTextureFormat(window)
+        }
+    };
     sdlpp::GPUGraphicsPipeline pipeline;
     pipeline.create(gpuDevice, {
         .vertexShader =  vertexShader,
-        .fragmentShader = fragmentShader
+        .fragmentShader = fragmentShader,
+        .targetInfo = {
+            .colorTargetDescriptions = colorTargetsDescs
+        }
     });
 
     bool running = true;
@@ -111,6 +128,8 @@ int main(int, char**)
         sdlpp::GPURenderPass renderPass = cmdBuffer.beginRenderPass({
             .colorTargetInfos = colorTargets
         });
+        renderPass.bindGraphicsPipeline(pipeline);
+        renderPass.drawPrimitives({.numVertices = 3});
 
         renderPass.end();
         cmdBuffer.submit();
diff --git a/private/sdl_gpu_test/sdlpp/gpu.hpp b/private/sdl_gpu_test/sdlpp/gpu.hpp
index 09aa304..ae92438 100644
--- a/private/sdl_gpu_test/sdlpp/gpu.hpp
+++ b/private/sdl_gpu_test/sdlpp/gpu.hpp
@@ -400,6 +400,14 @@ static_assert(sizeof(GPUDepthStencilTargetInfo) == sizeof(SDL_GPUDepthStencilTar
 // classes
 //
 
+struct GPUDrawPrimitivesArgs
+{
+    Uint32 numVertices = 0;
+    Uint32 numInstances = 1;
+    Uint32 firstVertex = 0;
+    Uint32 firstInstance = 0;
+};
+
 class GPURenderPass : public Base<SDL_GPURenderPass, GPURenderPass>
 {
 public:
@@ -426,6 +434,16 @@ public:
         MIJIN_ASSERT(mHandle == nullptr, "Renderpass has not been ended.");
     }
 
+    void bindGraphicsPipeline(SDL_GPUGraphicsPipeline* pipeline) const noexcept
+    {
+        SDL_BindGPUGraphicsPipeline(mHandle, pipeline);
+    }
+
+    void drawPrimitives(const GPUDrawPrimitivesArgs& args) const noexcept
+    {
+        SDL_DrawGPUPrimitives(mHandle, args.numVertices, args.numInstances, args.firstVertex, args.firstInstance);
+    }
+
     friend class GPUCommandBuffer;
 };
 
@@ -568,6 +586,12 @@ public:
         }
     }
 
+    [[nodiscard]]
+    GPUTextureFormat getSwapchainTextureFormat(SDL_Window* window) const
+    {
+        return static_cast<GPUTextureFormat>(SDL_GetGPUSwapchainTextureFormat(mHandle, window));
+    }
+
     [[nodiscard]]
     GPUCommandBuffer acquireCommandBuffer() const noexcept
     {