Add embedded MCP server for in-process UI introspection

api/rs/slint/Cargo.toml

@@ -75,6 +75,16 @@ unsafe-single-threaded = ["i-slint-core/unsafe-single-threaded"]
 ## APIs to support screen readers and other assistive technologies.
 accessibility = ["i-slint-backend-selector/accessibility"]
 
+## Enable the embedded MCP (Model Context Protocol) server for runtime UI introspection.
+##
+## When this feature is enabled and the `SLINT_MCP_PORT` environment variable is set at runtime,
+## the application starts an HTTP server that exposes the UI element tree, properties, and
+## interaction capabilities via the MCP protocol. This allows MCP clients (e.g. coding assistants)
+## to inspect and interact with the running application.
+##
+## Requires `SLINT_EMIT_DEBUG_INFO=1` at build time for full element information.
+mcp = ["i-slint-backend-selector/mcp"]
+
 ## Enable integration with [raw-window-handle](raw_window_handle_06) version 0.6. This provides a
 ## [`Window::window_handle()`] function that returns a struct that implements
 ## [HasWindowHandle](raw_window_handle_06::HasWindowHandle) and

internal/backends/selector/Cargo.toml

@@ -50,6 +50,7 @@ accessibility = ["i-slint-backend-winit?/accessibility"]
 raw-window-handle-06 = ["i-slint-core/raw-window-handle-06", "i-slint-backend-winit?/raw-window-handle-06"]
 
 system-testing = ["i-slint-backend-testing/system-testing"]
+mcp = ["i-slint-backend-testing/mcp"]
 
 unstable-wgpu-27 = [
   "i-slint-core/unstable-wgpu-27",

internal/backends/selector/lib.rs

@@ -172,6 +172,13 @@ pub fn with_global_context<R>(f: impl FnOnce(&SlintContext) -> R) -> Result<R, P
         i_slint_backend_testing::systest::init();
     }
 
+    #[cfg(feature = "mcp")]
+    if result.is_ok() && platform_created {
+        if let Err(e) = i_slint_backend_testing::mcp_server::init() {
+            i_slint_core::debug_log!("MCP server init failed: {e:?}");
+        }
+    }
+
     result
 }
 

internal/backends/testing/Cargo.toml

@@ -22,6 +22,7 @@ internal = ["include_dir"]
 # ffi for C++ bindings
 ffi = []
 system-testing = ["quick-protobuf", "pb-rs", "generational-arena", "async-net", "futures-lite", "byteorder", "image"]
+mcp = ["generational-arena", "async-net", "futures-lite", "image", "serde", "serde_json", "base64", "httparse"]
 
 [dependencies]
 i-slint-core = { workspace = true, features = ["std", "shared-parley"] }
@@ -33,6 +34,10 @@ async-net = { version = "2.0.0", optional = true }
 futures-lite = { version = "2.3.0", optional = true }
 byteorder = { version = "1.5.0", optional = true }
 image = { workspace = true, optional = true, features = ["png"] }
+serde = { workspace = true, optional = true }
+serde_json = { workspace = true, optional = true }
+base64 = { version = "0.22", optional = true }
+httparse = { version = "1", optional = true }
 include_dir = { version = "0.7", optional = true }
 
 [build-dependencies]