Add renderer draw descriptor contract

src/renderer_api/recording_renderer.cpp

@@ -316,7 +316,7 @@ pp::foundation::Status RecordingCommandContext::bind_mesh(IMesh& mesh) noexcept
     return pp::foundation::Status::success();
 }
 
-pp::foundation::Status RecordingCommandContext::draw() noexcept
+pp::foundation::Status RecordingCommandContext::draw(DrawDesc desc) noexcept
 {
     if (!in_render_pass_) {
         return pp::foundation::Status::invalid_argument("render pass has not begun");
@@ -328,9 +328,15 @@ pp::foundation::Status RecordingCommandContext::draw() noexcept
         return pp::foundation::Status::invalid_argument("mesh must be bound before draw");
     }
 
+    const auto draw_status = validate_draw_desc(active_mesh_, desc);
+    if (!draw_status.ok()) {
+        return draw_status;
+    }
+
     push_command(commands_, RecordedRenderCommand {
         .kind = RecordedRenderCommandKind::draw,
         .mesh_desc = active_mesh_,
+        .draw_desc = desc,
     });
     return pp::foundation::Status::success();
 }

src/renderer_api/recording_renderer.h

@@ -41,6 +41,7 @@ struct RecordedRenderCommand {
     BlendState blend_state {};
     DepthState depth_state {};
     MeshDesc mesh_desc {};
+    DrawDesc draw_desc {};
     TextureDesc texture_desc {};
     std::uint32_t texture_slot = 0;
     SamplerDesc sampler_desc {};
@@ -128,7 +129,7 @@ public:
         std::uint32_t slot,
         SamplerDesc sampler) noexcept override;
     [[nodiscard]] pp::foundation::Status bind_mesh(IMesh& mesh) noexcept override;
-    [[nodiscard]] pp::foundation::Status draw() noexcept override;
+    [[nodiscard]] pp::foundation::Status draw(DrawDesc desc) noexcept override;
     [[nodiscard]] pp::foundation::Status read_texture(
         ITexture2D& texture,
         ReadbackRegion region,

src/renderer_api/renderer_api.cpp

@@ -337,6 +337,40 @@ pp::foundation::Status validate_mesh_desc(MeshDesc desc) noexcept
     return pp::foundation::Status::invalid_argument("mesh topology is not supported");
 }
 
+pp::foundation::Status validate_draw_desc(MeshDesc mesh, DrawDesc draw) noexcept
+{
+    const auto mesh_status = validate_mesh_desc(mesh);
+    if (!mesh_status.ok()) {
+        return mesh_status;
+    }
+
+    if (draw.instance_count == 0) {
+        return pp::foundation::Status::invalid_argument("draw instance count must be greater than zero");
+    }
+
+    if (draw.vertex_count == 0 && draw.index_count == 0) {
+        return pp::foundation::Status::invalid_argument("draw must include vertices or indices");
+    }
+
+    if (draw.index_count > 0) {
+        if (mesh.index_count == 0) {
+            return pp::foundation::Status::invalid_argument("indexed draw requires an indexed mesh");
+        }
+
+        if (draw.first_index > mesh.index_count || draw.index_count > mesh.index_count - draw.first_index) {
+            return pp::foundation::Status::out_of_range("draw index range exceeds the bound mesh");
+        }
+
+        return pp::foundation::Status::success();
+    }
+
+    if (draw.first_vertex > mesh.vertex_count || draw.vertex_count > mesh.vertex_count - draw.first_vertex) {
+        return pp::foundation::Status::out_of_range("draw vertex range exceeds the bound mesh");
+    }
+
+    return pp::foundation::Status::success();
+}
+
 pp::foundation::Status validate_texture_slot(std::uint32_t slot) noexcept
 {
     if (slot >= max_texture_slots) {

src/renderer_api/renderer_api.h

@@ -157,6 +157,14 @@ struct MeshDesc {
     PrimitiveTopology topology = PrimitiveTopology::triangles;
 };
 
+struct DrawDesc {
+    std::uint32_t first_vertex = 0;
+    std::uint32_t vertex_count = 0;
+    std::uint32_t first_index = 0;
+    std::uint32_t index_count = 0;
+    std::uint32_t instance_count = 1;
+};
+
 struct ShaderStageSource {
     const char* entry_point = "main";
     const char* source = nullptr;
@@ -226,7 +234,7 @@ public:
         std::uint32_t slot,
         SamplerDesc sampler) noexcept = 0;
     [[nodiscard]] virtual pp::foundation::Status bind_mesh(IMesh& mesh) noexcept = 0;
-    [[nodiscard]] virtual pp::foundation::Status draw() noexcept = 0;
+    [[nodiscard]] virtual pp::foundation::Status draw(DrawDesc desc) noexcept = 0;
     [[nodiscard]] virtual pp::foundation::Status read_texture(
         ITexture2D& texture,
         ReadbackRegion region,
@@ -279,6 +287,7 @@ public:
 [[nodiscard]] pp::foundation::Status validate_sampler_address_mode(SamplerAddressMode mode) noexcept;
 [[nodiscard]] pp::foundation::Status validate_sampler_desc(SamplerDesc desc) noexcept;
 [[nodiscard]] pp::foundation::Status validate_mesh_desc(MeshDesc desc) noexcept;
+[[nodiscard]] pp::foundation::Status validate_draw_desc(MeshDesc mesh, DrawDesc draw) noexcept;
 [[nodiscard]] pp::foundation::Status validate_texture_slot(std::uint32_t slot) noexcept;
 [[nodiscard]] pp::foundation::Status validate_shader_program_desc(ShaderProgramDesc desc) noexcept;
 [[nodiscard]] pp::foundation::Status validate_shader_uniform_write(