diff --git a/Cargo.toml b/Cargo.toml
index 9ae2cbd32..7235bd524 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -6,6 +6,7 @@ members = [
     'sixtyfps_compiler/parser_test_macro',
     'api/sixtyfps-rs',
     'api/sixtyfps-rs/sixtyfps-rs-macro',
+    'tools/viewer',
     'examples/graphicstest',
     'examples/rusttest',
     'helper_crates/const-field-offset',
diff --git a/helper_crates/const-field-offset/src/lib.rs b/helper_crates/const-field-offset/src/lib.rs
index 125c3a927..cd4bf00ed 100644
--- a/helper_crates/const-field-offset/src/lib.rs
+++ b/helper_crates/const-field-offset/src/lib.rs
@@ -66,12 +66,12 @@ pub fn const_field_offset(input: TokenStream) -> TokenStream {
 
     // Build the output, possibly using quasi-quotation
     let expanded = quote! {
-        struct #field_struct_name {
-            #(#fields : usize,)*
+        pub struct #field_struct_name {
+            #(pub #fields : usize,)*
         }
 
         impl #struct_name {
-            /*pub ??? */ const fn field_offsets() -> #field_struct_name {
+            pub const fn field_offsets() -> #field_struct_name {
                 let mut len = 0usize;
                 #field_struct_name {
                     #( #fields : {
diff --git a/tools/viewer/Cargo.toml b/tools/viewer/Cargo.toml
new file mode 100644
index 000000000..4929e1138
--- /dev/null
+++ b/tools/viewer/Cargo.toml
@@ -0,0 +1,20 @@
+[package]
+name = "viewer"
+version = "0.1.0"
+authors = ["Olivier Goffart <ogoffart@sixtyfps.io>"]
+edition = "2018"
+
+
+[dependencies]
+corelib = { path="../../sixtyfps_runtime/corelib" }
+sixtyfps_compiler = { path = "../../sixtyfps_compiler", features = ["display-diagnostics"] }
+# FIXME: make optional and configurable backends
+gl = { path = "../../sixtyfps_runtime/rendering_backends/gl" }
+structopt = "0.3.14"
+codemap-diagnostic = "0.1.1"
+codemap = "0.1"
+
+
+[[bin]]
+name = "viewer"
+path = "main.rs"
diff --git a/tools/viewer/main.rs b/tools/viewer/main.rs
new file mode 100644
index 000000000..eb99ae7ca
--- /dev/null
+++ b/tools/viewer/main.rs
@@ -0,0 +1,175 @@
+use corelib::abi::datastructures::{ComponentImpl, ComponentType};
+use sixtyfps_compiler::object_tree::Expression;
+use std::collections::HashMap;
+use structopt::StructOpt;
+
+#[derive(StructOpt)]
+struct Cli {
+    #[structopt(name = "path to .60 file", parse(from_os_str))]
+    path: std::path::PathBuf,
+}
+
+trait PropertyWriter {
+    unsafe fn write(ptr: *mut u8, value: &Expression);
+}
+
+impl PropertyWriter for f32 {
+    unsafe fn write(ptr: *mut u8, value: &Expression) {
+        let val: Self = match value {
+            Expression::NumberLiteral(v) => *v as _,
+            _ => todo!(),
+        };
+        std::ptr::write(ptr as *mut Self, val);
+    }
+}
+
+impl PropertyWriter for u32 {
+    unsafe fn write(ptr: *mut u8, value: &Expression) {
+        let val: Self = match value {
+            Expression::NumberLiteral(v) => *v as _,
+            _ => todo!(),
+        };
+        std::ptr::write(ptr as *mut Self, val);
+    }
+}
+
+impl PropertyWriter for *const i8 {
+    unsafe fn write(ptr: *mut u8, value: &Expression) {
+        let val: Self = match value {
+            Expression::StringLiteral(v) => {
+                // FIXME that's a leak
+                std::ffi::CString::new(v.as_str()).unwrap().into_raw() as _
+            }
+            _ => todo!(),
+        };
+        std::ptr::write(ptr as *mut Self, val);
+    }
+}
+
+unsafe fn construct<T: Default>(ptr: *mut corelib::abi::datastructures::ItemImpl) {
+    core::ptr::write(ptr as *mut T, T::default());
+}
+
+unsafe fn set_property<T: PropertyWriter>(ptr: *mut u8, e: &Expression) {
+    T::write(ptr, e);
+}
+
+unsafe extern "C" fn dummy_destroy(_: *const ComponentType, _: *mut ComponentImpl) {
+    panic!();
+}
+
+#[repr(C)]
+struct MyComponentType {
+    ct: ComponentType,
+    it: Vec<corelib::abi::datastructures::ItemTreeNode>,
+}
+
+unsafe extern "C" fn item_tree(
+    c: *const ComponentType,
+) -> *const corelib::abi::datastructures::ItemTreeNode {
+    (*(c as *const MyComponentType)).it.as_ptr()
+}
+
+struct RuntimeTypeInfo {
+    vtable: *const corelib::abi::datastructures::ItemVTable,
+    construct: unsafe fn(*mut corelib::abi::datastructures::ItemImpl),
+    properties: HashMap<&'static str, (usize, unsafe fn(*mut u8, &Expression))>,
+    size: usize,
+}
+
+fn main() -> std::io::Result<()> {
+    use sixtyfps_compiler::*;
+    let args = Cli::from_args();
+    let source = std::fs::read_to_string(&args.path)?;
+    let (syntax_node, mut diag) = parser::parse(&source);
+    let tr = typeregister::TypeRegister::builtin();
+    let tree = object_tree::Document::from_node(syntax_node, &mut diag, &tr);
+    if !diag.inner.is_empty() {
+        diag.print(args.path.to_string_lossy().into_owned(), source);
+        std::process::exit(-1);
+    }
+
+    use corelib::abi::primitives::{Image, Rectangle};
+
+    // FIXME: thus obviously is unsafe and not great
+    let mut rtti = HashMap::new();
+    rtti.insert(
+        "Rectangle",
+        RuntimeTypeInfo {
+            vtable: &corelib::abi::primitives::RectangleVTable as _,
+            construct: construct::<Rectangle>,
+            properties: [
+                ("x", (Rectangle::field_offsets().x, set_property::<f32> as _)),
+                ("y", (Rectangle::field_offsets().y, set_property::<f32> as _)),
+                ("width", (Rectangle::field_offsets().width, set_property::<f32> as _)),
+                ("height", (Rectangle::field_offsets().height, set_property::<f32> as _)),
+                ("color", (Rectangle::field_offsets().color, set_property::<u32> as _)),
+            ]
+            .iter()
+            .cloned()
+            .collect(),
+            size: std::mem::size_of::<Rectangle>(),
+        },
+    );
+    rtti.insert(
+        "Image",
+        RuntimeTypeInfo {
+            vtable: &corelib::abi::primitives::ImageVTable as _,
+            construct: construct::<Image>,
+            properties: [
+                ("x", (Image::field_offsets().x, set_property::<f32> as _)),
+                ("y", (Image::field_offsets().y, set_property::<f32> as _)),
+                ("width", (Image::field_offsets().width, set_property::<f32> as _)),
+                ("height", (Image::field_offsets().height, set_property::<f32> as _)),
+                ("source", (Image::field_offsets().source, set_property::<*const i8> as _)),
+            ]
+            .iter()
+            .cloned()
+            .collect(),
+            size: std::mem::size_of::<Image>(),
+        },
+    );
+
+    let l = lower::LoweredComponent::lower(&*tree.root_component);
+
+    let mut tree_array = vec![];
+    let mut current_offset = 0usize;
+    let mut items_types = vec![];
+
+    generator::build_array_helper(&l, |item, child_offset| {
+        let rt = &rtti[&*item.native_type.class_name];
+        tree_array.push(corelib::abi::datastructures::ItemTreeNode::Item {
+            offset: current_offset as isize,
+            vtable: rt.vtable,
+            children_index: child_offset,
+            chilren_count: item.children.len() as _,
+        });
+        items_types.push((current_offset, rt, item.init_properties.clone()));
+        current_offset += rt.size;
+    });
+
+    let t = ComponentType { create: None, destroy: dummy_destroy, item_tree };
+    let t = MyComponentType { ct: t, it: tree_array };
+
+    let mut my_impl = Vec::<u64>::new();
+    my_impl.resize(current_offset / 8 + 1, 0);
+    let mem = my_impl.as_mut_ptr() as *mut u8;
+
+    for (offset, rtti, properties) in items_types {
+        unsafe {
+            let item = mem.offset(offset as isize);
+            (rtti.construct)(item as _);
+            for (prop, expr) in properties {
+                let (o, set) = rtti.properties[&*prop];
+                set(item.offset(o as isize), &expr);
+            }
+        }
+    }
+
+    gl::sixtyfps_runtime_run_component_with_gl_renderer(
+        &t as *const MyComponentType as *const ComponentType,
+        std::ptr::NonNull::new(mem).unwrap().cast(),
+    );
+
+    Ok(())
+}