Basic working circle render pipeline

src/GpuRender.zig

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+const std = @import("std");
+const c = @import("utils.zig").c;
+const sv = @import("utils.zig").sv;
+const GpuAllocator = @import("GpuAllocator.zig");
+const GpuBuffer = @import("GpuBuffer.zig");
+const GpuDevice = @import("GpuDevice.zig");
+
+pub const Binding = struct {
+    element_size: u32 = 0,
+};
+
+pub const RenderDef = struct {
+    bindings: []const Binding = &.{},
+    /// The surface texture format we are rendering to (e.g., BGRA8Unorm)
+    texture_format: c.WGPUTextureFormat,
+    /// The names of the entry points inside your WGSL code
+    vertex_entry: []const u8 = "vs_main",
+    fragment_entry: []const u8 = "fs_main",
+    /// Primitive topology, default to triangle list
+    topology: c.WGPUPrimitiveTopology = c.WGPUPrimitiveTopology_TriangleList,
+};
+
+pip: c.WGPURenderPipeline,
+def: RenderDef,
+
+pub fn init(device: GpuDevice, wgsl: []const u8, def: RenderDef) !@This() {
+    var wgsl_src = c.WGPUShaderSourceWGSL{
+        .chain = .{ .sType = c.WGPUSType_ShaderSourceWGSL },
+        .code = sv(wgsl),
+    };
+    const shader = c.wgpuDeviceCreateShaderModule(device.device, &.{
+        .nextInChain = @ptrCast(&wgsl_src),
+    }) orelse return error.Shader;
+    defer c.wgpuShaderModuleRelease(shader);
+
+    // 1. Setup the Color Target State (where the fragment shader outputs)
+    const blend = c.WGPUBlendState{
+        .color = .{ .operation = c.WGPUBlendOperation_Add, .srcFactor = c.WGPUBlendFactor_SrcAlpha, .dstFactor = c.WGPUBlendFactor_OneMinusSrcAlpha },
+        .alpha = .{ .operation = c.WGPUBlendOperation_Add, .srcFactor = c.WGPUBlendFactor_One, .dstFactor = c.WGPUBlendFactor_Zero },
+    };
+
+    const color_target = c.WGPUColorTargetState{
+        .format = def.texture_format,
+        .blend = &blend,
+        .writeMask = c.WGPUColorWriteMask_All,
+    };
+
+    // 2. Setup the Fragment State
+    const fragment_state = c.WGPUFragmentState{
+        .module = shader,
+        .entryPoint = sv(def.fragment_entry),
+        .targetCount = 1,
+        .targets = &color_target,
+    };
+
+    // 3. Compile the Complete Render Pipeline
+    const pip = c.wgpuDeviceCreateRenderPipeline(device.device, &.{
+        .vertex = .{
+            .module = shader,
+            .entryPoint = sv(def.vertex_entry),
+            .bufferCount = 0, // Assuming procedural drawing (like our circle!)
+        },
+        .primitive = .{
+            .topology = def.topology,
+            .stripIndexFormat = c.WGPUIndexFormat_Undefined,
+            .frontFace = c.WGPUFrontFace_CCW,
+            .cullMode = c.WGPUCullMode_None,
+        },
+        .multisample = .{
+            .count = 1,
+            .mask = 0xFFFFFFFF,
+            .alphaToCoverageEnabled = 0,
+        },
+        .fragment = &fragment_state,
+    }) orelse return error.Pipeline;
+
+    return .{
+        .pip = pip,
+        .def = def,
+    };
+}
+
+pub fn deinit(self: @This()) void {
+    c.wgpuRenderPipelineRelease(self.pip);
+}
+
+/// Execute the render pass targeting a specific frame texture view.
+/// Passes bind groups via a tuple exactly like your original compute setup.
+pub fn draw(
+    self: @This(),
+    gloc: GpuAllocator,
+    target_view: c.WGPUTextureView,
+    vertex_count: u32,
+    args: anytype,
+) !void {
+    const type_info = @typeInfo(@TypeOf(args));
+    if (type_info != .@"struct" or !type_info.@"struct".is_tuple)
+        @compileError("Expected a tuple of GpuBuffers for args. E.g. .{ uniform_buf }");
+
+    const fields = type_info.@"struct".fields;
+    if (fields.len != self.def.bindings.len)
+        return error.InvalidArgumentCount;
+
+    var entries_buf: [32]c.WGPUBindGroupEntry = undefined;
+
+    inline for (fields, 0..) |field, i| {
+        const buf = @field(args, field.name);
+        if (@TypeOf(buf) != GpuBuffer) {
+            @compileError("All arguments in the tuple must be of type GpuBuffer");
+        }
+        entries_buf[i] = .{
+            .binding = @intCast(i),
+            .buffer = buf.raw,
+            .offset = 0,
+            .size = buf.size,
+        };
+    }
+
+    const entries = entries_buf[0..fields.len];
+
+    // Create Render Bind Group from layout
+    const bgl = c.wgpuRenderPipelineGetBindGroupLayout(self.pip, 0);
+    defer c.wgpuBindGroupLayoutRelease(bgl);
+
+    const bg = c.wgpuDeviceCreateBindGroup(gloc.device.device, &.{
+        .layout = bgl,
+        .entries = entries.ptr,
+        .entryCount = @intCast(entries.len),
+    }) orelse return error.BindGroup;
+    defer c.wgpuBindGroupRelease(bg);
+
+    // Encode Render Command
+    const enc = c.wgpuDeviceCreateCommandEncoder(gloc.device.device, null) orelse return error.Encoder;
+    defer c.wgpuCommandEncoderRelease(enc);
+
+    const color_attachment = c.WGPURenderPassColorAttachment{
+        .view = target_view,
+        .resolveTarget = null,
+        .loadOp = c.WGPULoadOp_Clear,
+        .storeOp = c.WGPUStoreOp_Store,
+        .clearValue = .{ .r = 0.1, .g = 0.1, .b = 0.1, .a = 1.0 },
+        .depthSlice = c.WGPU_DEPTH_SLICE_UNDEFINED,
+    };
+
+    const pass_desc = c.WGPURenderPassDescriptor{
+        .colorAttachmentCount = 1,
+        .colorAttachments = &color_attachment,
+        .depthStencilAttachment = null,
+    };
+
+    const pass = c.wgpuCommandEncoderBeginRenderPass(enc, &pass_desc);
+    c.wgpuRenderPassEncoderSetPipeline(pass, self.pip);
+
+    if (fields.len > 0) {
+        c.wgpuRenderPassEncoderSetBindGroup(pass, 0, bg, 0, null);
+    }
+
+    // Draw! (Instead of Compute Dispatch)
+    c.wgpuRenderPassEncoderDraw(pass, vertex_count, 1, 0, 0);
+
+    c.wgpuRenderPassEncoderEnd(pass);
+    c.wgpuRenderPassEncoderRelease(pass);
+
+    const cmd = c.wgpuCommandEncoderFinish(enc, null);
+    defer c.wgpuCommandBufferRelease(cmd);
+
+    c.wgpuQueueSubmit(gloc.device.queue, 1, &cmd);
+}