Implement property declarations for the C++ backend

examples/cpptest/hello.60

@@ -77,7 +77,8 @@ Hello := Rectangle {
             color: black;
         }
     }
-    counter := Text { x: 100; y: 300; text: "0"; color: black; }
+    property<int32> counter;
+    counter_label := Text { x: 100; y: 300; text: "0"; color: black; }
     ButtonRectangle {
         color: 4289374890;
         x: 50;

examples/cpptest/main.cpp

@@ -4,24 +4,24 @@
 int main() {
     static Hello component;
 
-    static int counter = 0;
-
     component._foobar.set_handler([](auto...){
         std::cout << "Hello from C++" << std::endl;
     });
 
     component._plus_clicked.set_handler([](auto...){
-        counter += 1;
+        auto &counter = component.property_0_counter;
+        counter.set(counter.get() + 1);
         // FIXME: this _13 is an internal detail and should be private anyway.  We muse use some
         // alias or way to expose the property  (same for the _ before signals)
-        component.counter_13.text.set(std::string_view(std::to_string(counter)));
-        std::cout << "PLUS: " << std::string_view(component.counter_13.text.get()) << std::endl;
+        component.counter_label_13.text.set(std::string_view(std::to_string(counter.get())));
+        std::cout << "PLUS: " << std::string_view(component.counter_label_13.text.get()) << std::endl;
     });
 
     component._minus_clicked.set_handler([](auto...){
-        counter -= 1;
-        component.counter_13.text.set(std::string_view(std::to_string(counter)));
-        std::cout << "MINUS: " << std::string_view(component.counter_13.text.get()) << std::endl;
+        auto &counter = component.property_0_counter;
+        counter.set(counter.get() - 1);
+        component.counter_label_13.text.set(std::string_view(std::to_string(counter.get())));
+        std::cout << "MINUS: " << std::string_view(component.counter_label_13.text.get()) << std::endl;
     });
 
     sixtyfps::run(&component);

sixtyfps_compiler/generator/cpp.rs

@@ -121,12 +121,35 @@ mod cpp_ast {
             writeln!(f, ";")
         }
     }
+
+    pub trait CppType {
+        fn cpp_type(&self) -> Option<&str>;
+    }
 }
 
 use crate::lower::{LoweredComponent, LoweredItem};
+use crate::typeregister::Type;
 use cpp_ast::*;
 
-fn handle_item(item: &LoweredItem, main_struct: &mut Struct, init: &mut Vec<String>) {
+impl CppType for Type {
+    fn cpp_type(&self) -> Option<&str> {
+        match self {
+            Type::Float32 => Some("float"),
+            Type::Int32 => Some("int"),
+            Type::String => Some("sixtyfps::SharedString"),
+            Type::Color => Some("uint32_t"),
+            Type::Bool => Some("bool"),
+            _ => None,
+        }
+    }
+}
+
+fn handle_item(
+    item: &LoweredItem,
+    global_properties: &Vec<String>,
+    main_struct: &mut Struct,
+    init: &mut Vec<String>,
+) {
     main_struct.members.push(Declaration::Var(Var {
         ty: format!("sixtyfps::{}", item.native_type.class_name),
         name: item.id.clone(),
@@ -135,13 +158,19 @@ fn handle_item(item: &LoweredItem, main_struct: &mut Struct, init: &mut Vec<Stri
 
     let id = &item.id;
     init.extend(item.init_properties.iter().map(|(s, i)| {
+        let cpp_prop = item
+            .property_declarations
+            .get(s)
+            .map(|idx| global_properties[*idx].clone())
+            .unwrap_or_else(|| format!("{id}.{prop}", id = id, prop = s.clone()));
+
         use crate::expression_tree::Expression::*;
         let init = match &i {
             StringLiteral(s) => format!(r#"sixtyfps::SharedString("{}")"#, s.escape_default()),
             NumberLiteral(n) => n.to_string(),
             _ => format!("\n#error: unsupported expression {:?}\n", i),
         };
-        format!("{id}.{prop}.set({init});", id = id, prop = s, init = init)
+        format!("{cpp_prop}.set({init});", cpp_prop = cpp_prop, init = init)
     }));
     init.extend(item.connect_signals.iter().map(|(s, fwd)| {
         format!(
@@ -151,7 +180,7 @@ fn handle_item(item: &LoweredItem, main_struct: &mut Struct, init: &mut Vec<Stri
     }));
 
     for i in &item.children {
-        handle_item(i, main_struct, init)
+        handle_item(i, global_properties, main_struct, init)
     }
 }
 
@@ -163,8 +192,31 @@ pub fn generate(component: &LoweredComponent) -> impl std::fmt::Display {
 
     let mut main_struct = Struct { name: component.id.clone(), ..Default::default() };
 
+    let (declared_property_members, declared_property_vars): (Vec<String>, Vec<Declaration>) =
+        component
+            .property_declarations
+            .iter()
+            .enumerate()
+            .map(|(index, property)| {
+                let cpp_name: String = format!("property_{}_{}", index, property.name_hint).into();
+                (
+                    cpp_name.clone(),
+                    Declaration::Var(Var {
+                        ty: format!(
+                            "sixtyfps::Property<{}>",
+                            property.property_type.cpp_type().expect("cannot convert type to C++")
+                        ),
+                        name: cpp_name,
+                        init: None,
+                    }),
+                )
+            })
+            .unzip();
+
+    main_struct.members.extend(declared_property_vars);
+
     let mut init = Vec::new();
-    handle_item(&component.root_item, &mut main_struct, &mut init);
+    handle_item(&component.root_item, &declared_property_members, &mut main_struct, &mut init);
 
     main_struct.members.extend(component.signals_declarations.iter().map(|s| {
         Declaration::Var(Var { ty: "sixtyfps::Signal".into(), name: s.clone(), init: None })

sixtyfps_compiler/lower.rs

@@ -15,6 +15,8 @@ pub struct NativeItemType {
     pub class_name: String,
 }
 
+pub type LoweredPropertyDeclarationIndex = usize;
+
 #[derive(Default, Debug)]
 pub struct LoweredItem {
     pub id: String,
@@ -22,6 +24,7 @@ pub struct LoweredItem {
     pub init_properties: HashMap<String, Expression>,
     /// Right now we only allow forwarding and this connect with the signal in the root
     pub connect_signals: HashMap<String, String>,
+    pub property_declarations: HashMap<String, LoweredPropertyDeclarationIndex>,
     pub children: Vec<LoweredItem>,
 }
 
@@ -31,6 +34,7 @@ pub struct LoweredComponent {
     pub root_item: LoweredItem,
 
     pub signals_declarations: Vec<String>,
+    pub property_declarations: Vec<LoweredPropertyDeclaration>,
 }
 
 impl LoweredComponent {
@@ -40,6 +44,7 @@ impl LoweredComponent {
             id: component.id.clone(),
             root_item: LoweredComponent::lower_item(&*component.root_element.borrow(), &mut state),
             signals_declarations: state.signals,
+            property_declarations: state.property_declarations,
         }
     }
 
@@ -72,6 +77,16 @@ impl LoweredComponent {
         let current_component_id = state.current_component_id.clone();
         let format_signal = |name| format!("{}_{}", current_component_id, name);
         state.signals.extend(element.signals_declaration.iter().map(format_signal));
+
+        for (prop_name, property_type) in element.property_declarations.iter() {
+            let component_global_index = state.property_declarations.len();
+            lowered.property_declarations.insert(prop_name.clone(), component_global_index);
+            state.property_declarations.push(LoweredPropertyDeclaration {
+                property_type: property_type.clone(),
+                name_hint: prop_name.clone(),
+            });
+        }
+
         for (k, e) in element.bindings.iter() {
             if let Expression::SignalReference { name, .. } = e {
                 lowered.connect_signals.insert(
@@ -89,6 +104,12 @@ impl LoweredComponent {
     }
 }
 
+#[derive(Debug)]
+pub struct LoweredPropertyDeclaration {
+    pub property_type: Type,
+    pub name_hint: String,
+}
+
 #[derive(Default)]
 struct LowererState {
     /// The count of item to create the ids
@@ -97,4 +118,5 @@ struct LowererState {
     current_component_id: String,
 
     signals: Vec<String>,
+    property_declarations: Vec<LoweredPropertyDeclaration>,
 }