Add renderer blend state contract

tools/pano_cli/main.cpp

@@ -2273,6 +2273,13 @@ int record_render(int argc, char** argv)
     }
 
     const auto shader_status = context.bind_shader(shader);
+    const auto blend_status = context.set_blend_state(pp::renderer::BlendState {
+        .enabled = true,
+        .source_color = pp::renderer::BlendFactor::source_alpha,
+        .destination_color = pp::renderer::BlendFactor::one_minus_source_alpha,
+        .source_alpha = pp::renderer::BlendFactor::one,
+        .destination_alpha = pp::renderer::BlendFactor::one_minus_source_alpha,
+    });
     const auto bind_texture_status = context.bind_texture(0, texture);
     const auto mesh_status = context.bind_mesh(mesh);
     const auto draw_status = context.draw();
@@ -2282,6 +2289,10 @@ int record_render(int argc, char** argv)
         print_error("record-render", shader_status.message);
         return 2;
     }
+    if (!blend_status.ok()) {
+        print_error("record-render", blend_status.message);
+        return 2;
+    }
     if (!bind_texture_status.ok()) {
         print_error("record-render", bind_texture_status.message);
         return 2;
@@ -2337,6 +2348,7 @@ int record_render(int argc, char** argv)
     }
 
     std::size_t draw_commands = 0;
+    std::size_t blend_commands = 0;
     std::size_t bind_texture_commands = 0;
     std::size_t upload_commands = 0;
     std::size_t readback_commands = 0;
@@ -2353,6 +2365,8 @@ int record_render(int argc, char** argv)
     for (const auto& command : commands) {
         if (command.kind == pp::renderer::RecordedRenderCommandKind::draw) {
             ++draw_commands;
+        } else if (command.kind == pp::renderer::RecordedRenderCommandKind::set_blend_state) {
+            ++blend_commands;
         } else if (command.kind == pp::renderer::RecordedRenderCommandKind::bind_texture) {
             ++bind_texture_commands;
             const auto bound_bytes = pp::renderer::texture_byte_size(command.texture_desc);
@@ -2384,6 +2398,7 @@ int record_render(int argc, char** argv)
               << ",\"format\":\"rgba8\"}"
               << ",\"commands\":" << commands.size()
               << ",\"drawCommands\":" << draw_commands
+              << ",\"blendCommands\":" << blend_commands
               << ",\"bindTextureCommands\":" << bind_texture_commands
               << ",\"boundTextureBytes\":" << bound_texture_bytes
               << ",\"uploadCommands\":" << upload_commands