Lay out items on a path

This works, but it's still missing support for positioning of the layout
itself.

api/sixtyfps-cpp/include/sixtyfps.h

@@ -78,11 +78,14 @@ EvaluationContext evaluation_context_for_root_component(const Component *compone
 }
 
 // layouts:
-using internal::Slice;
+using internal::Constraint;
-using internal::solve_grid_layout;
 using internal::GridLayoutCellData;
 using internal::GridLayoutData;
-using internal::Constraint;
+using internal::PathLayoutData;
+using internal::PathLayoutItemData;
+using internal::Slice;
+using internal::solve_grid_layout;
+using internal::solve_path_layout;
 
 // models
 

api/sixtyfps-rs/lib.rs

@@ -81,7 +81,8 @@ pub mod re_exports {
     pub use sixtyfps_corelib::abi::slice::Slice;
     pub use sixtyfps_corelib::item_tree::visit_item_tree;
     pub use sixtyfps_corelib::layout::{
-        solve_grid_layout, Constraint, GridLayoutCellData, GridLayoutData,
+        solve_grid_layout, solve_path_layout, Constraint, GridLayoutCellData, GridLayoutData,
+        PathLayoutData, PathLayoutItemData,
     };
     pub use sixtyfps_corelib::Color;
     pub use sixtyfps_corelib::ComponentVTable_static;

sixtyfps_compiler/generator/cpp.rs

@@ -833,50 +833,7 @@ fn compile_expression(e: &crate::expression_tree::Expression, component: &Rc<Com
                 panic!("Expression::Object is not a Type::Object")
             }
         }
-        PathElements { elements } => match elements {
+        PathElements { elements } => compile_path(elements, component),
-            crate::expression_tree::Path::Elements(elements) => {
-                let converted_elements: Vec<String> = elements
-                    .iter()
-                    .map(|element| {
-                        let element_initializer = element
-                            .element_type
-                            .cpp_type
-                            .as_ref()
-                            .map(|cpp_type| {
-                                new_struct_with_bindings(&cpp_type, &element.bindings, component)
-                            })
-                            .unwrap_or_default();
-                        format!(
-                            "sixtyfps::PathElement::{}({})",
-                            element.element_type.class_name, element_initializer
-                        )
-                    })
-                    .collect();
-                format!(
-                    r#"[&](){{
-                    sixtyfps::PathElement elements[{}] = {{
-                        {}
-                    }};
-                    return sixtyfps::PathElements(&elements[0], sizeof(elements) / sizeof(elements[0]));
-                }}()"#,
-                    converted_elements.len(),
-                    converted_elements.join(",")
-                )
-            }
-            crate::expression_tree::Path::Events(events) => {
-                let converted_elements: Vec<String> = compile_path_events(events);
-                format!(
-                    r#"[&](){{
-                    sixtyfps::PathEvent events[{}] = {{
-                        {}
-                    }};
-                    return sixtyfps::PathElements(&events[0], sizeof(events) / sizeof(events[0]));
-                }}()"#,
-                    converted_elements.len(),
-                    converted_elements.join(",")
-                )
-            }
-        },
         Uncompiled(_) => panic!(),
         Invalid => format!("\n#error invalid expression\n"),
     }
@@ -889,7 +846,7 @@ fn compute_layout(component: &Rc<Component>) -> Vec<String> {
         "[[maybe_unused]] auto self = reinterpret_cast<const {ty}*>(component.instance);",
         ty = component_id(component)
     ));
-    for grid in component.layout_constraints.borrow().0.iter() {
+    for grid in component.layout_constraints.borrow().grids.iter() {
         res.push("{".to_owned());
         res.push(format!("    std::array<sixtyfps::Constraint, {}> row_constr;", grid.row_count()));
         res.push(format!("    std::array<sixtyfps::Constraint, {}> col_constr;", grid.col_count()));
@@ -943,6 +900,33 @@ fn compute_layout(component: &Rc<Component>) -> Vec<String> {
         res.push("    sixtyfps::solve_grid_layout(&grid);".to_owned());
         res.push("}".to_owned());
     }
+
+    for path_layout in component.layout_constraints.borrow().paths.iter() {
+        res.push("{".to_owned());
+
+        res.push("    sixtyfps::PathLayoutItemData items[] = {".to_owned());
+        for item in &path_layout.elements {
+            let p = |n: &str| {
+                if item.borrow().lookup_property(n) == Type::Float32 {
+                    format!("&self->{}.{}", item.borrow().id, n)
+                } else {
+                    "nullptr".to_owned()
+                }
+            };
+            res.push(format!("        {{ {}, {} }},", p("x"), p("y")));
+        }
+        res.push("    };".to_owned());
+
+        res.push(format!("    auto path = {};", compile_path(&path_layout.path, component)));
+
+        res.push("    sixtyfps::PathLayoutData pl { ".into());
+        res.push("        &path,".to_owned());
+        res.push("        {items, std::size(items)}".to_owned());
+        res.push("    };".to_owned());
+        res.push("    sixtyfps::solve_path_layout(&pl);".to_owned());
+        res.push("}".to_owned());
+    }
+
     res
 }
 
@@ -963,6 +947,53 @@ fn new_path_event(event_name: &str, fields: &[(&str, String)]) -> String {
     )
 }
 
+fn compile_path(path: &crate::expression_tree::Path, component: &Rc<Component>) -> String {
+    match path {
+        crate::expression_tree::Path::Elements(elements) => {
+            let converted_elements: Vec<String> = elements
+                .iter()
+                .map(|element| {
+                    let element_initializer = element
+                        .element_type
+                        .cpp_type
+                        .as_ref()
+                        .map(|cpp_type| {
+                            new_struct_with_bindings(&cpp_type, &element.bindings, component)
+                        })
+                        .unwrap_or_default();
+                    format!(
+                        "sixtyfps::PathElement::{}({})",
+                        element.element_type.class_name, element_initializer
+                    )
+                })
+                .collect();
+            format!(
+                r#"[&](){{
+                sixtyfps::PathElement elements[{}] = {{
+                    {}
+                }};
+                return sixtyfps::PathElements(&elements[0], sizeof(elements) / sizeof(elements[0]));
+            }}()"#,
+                converted_elements.len(),
+                converted_elements.join(",")
+            )
+        }
+        crate::expression_tree::Path::Events(events) => {
+            let converted_elements: Vec<String> = compile_path_events(events);
+            format!(
+                r#"[&](){{
+                sixtyfps::PathEvent events[{}] = {{
+                    {}
+                }};
+                return sixtyfps::PathElements(&events[0], sizeof(events) / sizeof(events[0]));
+            }}()"#,
+                converted_elements.len(),
+                converted_elements.join(",")
+            )
+        }
+    }
+}
+
 fn compile_path_events(events: &crate::expression_tree::PathEvents) -> Vec<String> {
     use lyon::path::Event;
 

sixtyfps_compiler/generator/rust.rs

@@ -2,7 +2,7 @@
 */
 
 use crate::diagnostics::{CompilerDiagnostic, Diagnostics};
-use crate::expression_tree::{Expression, NamedReference, OperatorClass};
+use crate::expression_tree::{Expression, NamedReference, OperatorClass, Path};
 use crate::object_tree::{Component, ElementRc};
 use crate::parser::Spanned;
 use crate::typeregister::Type;
@@ -678,58 +678,13 @@ fn compile_expression(e: &Expression, component: &Rc<Component>) -> TokenStream
                 panic!("Expression::Object is not a Type::Object")
             }
         }
-        Expression::PathElements { elements } => match elements {
+        Expression::PathElements { elements } => compile_path(elements, component),
-            crate::expression_tree::Path::Elements(elements) => {
-                let converted_elements: Vec<TokenStream> = elements
-                    .iter()
-                    .map(|element| {
-                        let mut bindings = element
-                            .bindings
-                            .iter()
-                            .map(|(property, expr)| {
-                                let prop_ident = quote::format_ident!("{}", property);
-                                let binding_expr = compile_expression(expr, component);
-
-                                quote!(#prop_ident: #binding_expr as _).to_string()
-                            })
-                            .collect::<Vec<String>>();
-
-                        if bindings.len() < element.element_type.properties.len() {
-                            bindings.push("..Default::default()".into())
-                        }
-
-                        let bindings = bindings.join(",");
-
-                        let ctor_format_string = element
-                        .element_type
-                        .rust_type_constructor
-                        .as_ref()
-                        .expect(
-                        "Unexpected error in type registry: path element is lacking rust type name",
-                    );
-
-                        ctor_format_string
-                            .replace("{}", &bindings)
-                            .parse()
-                            .expect("Error parsing rust path element constructor")
-                    })
-                    .collect();
-
-                quote!(sixtyfps::re_exports::PathElements::SharedElements(
-                    sixtyfps::re_exports::SharedArray::<sixtyfps::re_exports::PathElement>::from(&[#(#converted_elements),*])
-                ))
-            }
-            crate::expression_tree::Path::Events(events) => {
-                let events = compile_path_events(events);
-                quote!(sixtyfps::re_exports::PathElements::PathEvents(#events))
-            }
-        },
     }
 }
 
-fn compute_layout(component: &Component) -> TokenStream {
+fn compute_layout(component: &Rc<Component>) -> TokenStream {
     let mut layouts = vec![];
-    for x in component.layout_constraints.borrow().0.iter() {
+    for x in component.layout_constraints.borrow().grids.iter() {
         let within = quote::format_ident!("{}", x.within.borrow().id);
         let within_ty =
             quote::format_ident!("{}", x.within.borrow().base_type.as_builtin().class_name);
@@ -784,6 +739,39 @@ fn compute_layout(component: &Component) -> TokenStream {
         });
     }
 
+    for path_layout in component.layout_constraints.borrow().paths.iter() {
+        let items = path_layout
+            .elements
+            .iter()
+            .map(|elem| {
+                let e = quote::format_ident!("{}", elem.borrow().id);
+                let p = |n: &str| {
+                    if elem.borrow().lookup_property(n) == Type::Float32 {
+                        let n = quote::format_ident!("{}", n);
+                        quote! {Some(&self.#e.#n)}
+                    } else {
+                        quote! {None}
+                    }
+                };
+                let x = p("x");
+                let y = p("y");
+                quote!(PathLayoutItemData {
+                    x: #x,
+                    y: #y,
+                })
+            })
+            .collect::<Vec<_>>();
+
+        let path = compile_path(&path_layout.path, &component);
+
+        layouts.push(quote! {
+            solve_path_layout(&PathLayoutData {
+                items: Slice::from_slice(&[#( #items ),*]),
+                elements: &#path,
+            });
+        });
+    }
+
     quote! {
         fn layout_info(self: ::core::pin::Pin<&Self>) -> sixtyfps::re_exports::LayoutInfo {
             todo!("Implement in rust.rs")
@@ -848,3 +836,52 @@ fn compile_path_events(events: &crate::expression_tree::PathEvents) -> TokenStre
 
     quote!(sixtyfps::re_exports::SharedArray::<sixtyfps::re_exports::PathEvent>::from(&[#(#converted_events),*]))
 }
+
+fn compile_path(path: &Path, component: &Rc<Component>) -> TokenStream {
+    match path {
+        Path::Elements(elements) => {
+            let converted_elements: Vec<TokenStream> = elements
+                .iter()
+                .map(|element| {
+                    let mut bindings = element
+                        .bindings
+                        .iter()
+                        .map(|(property, expr)| {
+                            let prop_ident = quote::format_ident!("{}", property);
+                            let binding_expr = compile_expression(expr, component);
+
+                            quote!(#prop_ident: #binding_expr as _).to_string()
+                        })
+                        .collect::<Vec<String>>();
+
+                    if bindings.len() < element.element_type.properties.len() {
+                        bindings.push("..Default::default()".into())
+                    }
+
+                    let bindings = bindings.join(",");
+
+                    let ctor_format_string = element
+                        .element_type
+                        .rust_type_constructor
+                        .as_ref()
+                        .expect(
+                        "Unexpected error in type registry: path element is lacking rust type name",
+                    );
+
+                    ctor_format_string
+                        .replace("{}", &bindings)
+                        .parse()
+                        .expect("Error parsing rust path element constructor")
+                })
+                .collect();
+
+            quote!(sixtyfps::re_exports::PathElements::SharedElements(
+                sixtyfps::re_exports::SharedArray::<sixtyfps::re_exports::PathElement>::from(&[#(#converted_elements),*])
+            ))
+        }
+        Path::Events(events) => {
+            let events = compile_path_events(events);
+            quote!(sixtyfps::re_exports::PathElements::PathEvents(#events))
+        }
+    }
+}

sixtyfps_compiler/layout.rs

@@ -1,9 +1,13 @@
 //! Datastructures used to represent layouts in the compiler
 
+use crate::expression_tree::Path;
 use crate::object_tree::ElementRc;
 
 #[derive(Default, Debug)]
-pub struct LayoutConstraints(pub Vec<GridLayout>);
+pub struct LayoutConstraints {
+    pub grids: Vec<GridLayout>,
+    pub paths: Vec<PathLayout>,
+}
 
 /// Internal representation of a grid layout
 #[derive(Debug)]
@@ -24,3 +28,10 @@ impl GridLayout {
         self.elems.len()
     }
 }
+
+/// Internal representation of a path layout
+#[derive(Debug)]
+pub struct PathLayout {
+    pub path: Path,
+    pub elements: Vec<ElementRc>,
+}

sixtyfps_compiler/passes/compile_paths.rs

@@ -71,14 +71,13 @@ pub fn compile_paths(
                 }
             }
         } else {
-            let mut children = std::mem::take(&mut elem.children);
+            let new_children = Vec::with_capacity(elem.children.len());
+            let old_children = std::mem::replace(&mut elem.children, new_children);
 
-            crate::expression_tree::Path::Elements(
+            let mut path_data = Vec::new();
-                children
+
-                    .iter_mut()
+            for child in old_children {
-                    .filter_map(|child| {
+                let element_name = &child.borrow().base_type.as_builtin().class_name.clone();
-                        let mut child = child.borrow_mut();
-                        let element_name = &child.base_type.as_builtin().class_name;
 
                 if let Some(path_element) = element_types.get(element_name) {
                     let element_type = match path_element {
@@ -88,14 +87,13 @@ pub fn compile_paths(
                             element_name
                         ),
                     };
-                            let bindings = std::mem::take(&mut child.bindings);
+                    let bindings = std::mem::take(&mut child.borrow_mut().bindings);
-                            Some(PathElement { element_type, bindings })
+                    path_data.push(PathElement { element_type, bindings });
                 } else {
-                            None
+                    elem.children.push(child);
                 }
-                    })
+            }
-                    .collect(),
+            crate::expression_tree::Path::Elements(path_data)
-            )
         };
 
         elem.bindings.insert("elements".into(), Expression::PathElements { elements: path_data });

sixtyfps_compiler/passes/lower_layout.rs

@@ -2,6 +2,7 @@
 
 use crate::diagnostics::Diagnostics;
 
+use crate::expression_tree::*;
 use crate::layout::*;
 use crate::object_tree::*;
 use std::rc::Rc;
@@ -14,7 +15,7 @@ pub fn lower_layouts(component: &Rc<Component>, diag: &mut Diagnostics) {
         let old_children = std::mem::replace(&mut elem.children, new_children);
 
         for child in old_children {
-            let is_layout =
+            let is_grid_layout =
                 if let crate::typeregister::Type::Builtin(be) = &child.borrow().base_type {
                     assert!(be.class_name != "Row"); // Caught at element lookup time
                     be.class_name == "GridLayout"
@@ -22,7 +23,14 @@ pub fn lower_layouts(component: &Rc<Component>, diag: &mut Diagnostics) {
                     false
                 };
 
-            if is_layout {
+            let is_path_layout =
+                if let crate::typeregister::Type::Builtin(be) = &child.borrow().base_type {
+                    be.class_name == "PathLayout"
+                } else {
+                    false
+                };
+
+            if is_grid_layout {
                 let mut grid = GridLayout { within: elem_.clone(), elems: Default::default() };
                 let mut row = 0;
                 let mut col = 0;
@@ -53,7 +61,26 @@ pub fn lower_layouts(component: &Rc<Component>, diag: &mut Diagnostics) {
                     }
                 }
                 component.optimized_elements.borrow_mut().push(child.clone());
-                component.layout_constraints.borrow_mut().0.push(grid);
+                component.layout_constraints.borrow_mut().grids.push(grid);
+                continue;
+            } else if is_path_layout {
+                let layout_elem = child;
+                let layout_children = std::mem::take(&mut layout_elem.borrow_mut().children);
+                elem.children.extend(layout_children.iter().cloned());
+                component.optimized_elements.borrow_mut().push(layout_elem.clone());
+                let path_elements_expr = match layout_elem.borrow_mut().bindings.remove("elements")
+                {
+                    Some(Expression::PathElements { elements }) => elements,
+                    _ => {
+                        diag.push_error("Internal error: elements binding in PathLayout does not contain path elements expression".into(), layout_elem.borrow().span());
+                        return;
+                    }
+                };
+                component
+                    .layout_constraints
+                    .borrow_mut()
+                    .paths
+                    .push(PathLayout { elements: layout_children, path: path_elements_expr });
                 continue;
             } else {
                 elem.children.push(child);

sixtyfps_runtime/interpreter/dynamic_component.rs

@@ -500,7 +500,7 @@ unsafe extern "C" fn compute_layout(component: ComponentRefPin, eval_context: &E
     let component_type =
         &*(component.get_vtable() as *const ComponentVTable as *const ComponentDescription);
 
-    for it in &component_type.original.layout_constraints.borrow().0 {
+    for it in &component_type.original.layout_constraints.borrow().grids {
         use sixtyfps_corelib::layout::*;
 
         let mut row_constraint = vec![];
@@ -557,6 +557,32 @@ unsafe extern "C" fn compute_layout(component: ComponentRefPin, eval_context: &E
             cells: Slice::from(cells.as_slice()),
         });
     }
+
+    for it in &component_type.original.layout_constraints.borrow().paths {
+        use sixtyfps_corelib::layout::*;
+
+        let items = it
+            .elements
+            .iter()
+            .map(|elem| {
+                let info = &component_type.items[elem.borrow().id.as_str()];
+                let get_prop = |name| {
+                    info.rtti.properties.get(name).map(|p| {
+                        &*(component.as_ptr().add(info.offset).add(p.offset())
+                            as *const Property<f32>)
+                    })
+                };
+                PathLayoutItemData { x: get_prop("x"), y: get_prop("y") }
+            })
+            .collect::<Vec<_>>();
+
+        let path_elements = eval::convert_path(&it.path, component_type, eval_context);
+
+        solve_path_layout(&PathLayoutData {
+            items: Slice::from(items.as_slice()),
+            elements: &path_elements,
+        });
+    }
 }
 
 /// Get the component description from a ComponentRef

sixtyfps_runtime/interpreter/eval.rs

@@ -323,22 +323,7 @@ pub fn eval_expression(
                 .collect(),
         ),
         Expression::PathElements { elements } => {
-            match elements {
+            Value::PathElements(convert_path(elements, component_type, eval_context))
-                ExprPath::Elements(elements) => Value::PathElements(PathElements::SharedElements(
-                    sixtyfps_corelib::SharedArray::<
-                        sixtyfps_corelib::abi::datastructures::PathElement,
-                    >::from_iter(elements.iter().map(|element| {
-                        convert_path_element(element, component_type, eval_context)
-                    })),
-                )),
-                ExprPath::Events(events) => {
-                    Value::PathElements(PathElements::PathEvents(sixtyfps_corelib::SharedArray::<
-                        sixtyfps_corelib::abi::datastructures::PathEvent,
-                    >::from_iter(
-                        events.iter().map(|event| event.into()),
-                    )))
-                }
-            }
         }
     }
 }
@@ -378,6 +363,29 @@ pub fn new_struct_with_bindings<
     element
 }
 
+pub fn convert_path(
+    path: &ExprPath,
+    component_type: &crate::ComponentDescription,
+    eval_context: &corelib::EvaluationContext,
+) -> sixtyfps_corelib::abi::datastructures::PathElements {
+    match path {
+        ExprPath::Elements(elements) => {
+            PathElements::SharedElements(sixtyfps_corelib::SharedArray::<
+                sixtyfps_corelib::abi::datastructures::PathElement,
+            >::from_iter(
+                elements
+                    .iter()
+                    .map(|element| convert_path_element(element, component_type, eval_context)),
+            ))
+        }
+        ExprPath::Events(events) => PathElements::PathEvents(sixtyfps_corelib::SharedArray::<
+            sixtyfps_corelib::abi::datastructures::PathEvent,
+        >::from_iter(
+            events.iter().map(|event| event.into()),
+        )),
+    }
+}
+
 fn convert_path_element(
     expr_element: &ExprPathElement,
     component_type: &crate::ComponentDescription,

tests/cases/path_layout.60

@@ -0,0 +1,28 @@
+TestCase := Rectangle {
+
+    Path {
+        commands: "M 100 300 Q 150 50 250 150 C 250 300 300 300 300 450 A 50 50 0 1 0 450 450 L 550 300";
+        stroke_color: black;
+        stroke_width: 2;
+    }
+
+    PathLayout {
+        commands: "M 100 300 Q 150 50 250 150 C 250 300 300 300 300 450 A 50 50 0 1 0 450 450 L 550 300";
+
+        Text {
+            text: "First item on path";
+            color: black;
+        }
+
+        Text {
+            text: "Second item on path";
+            color: black;
+        }
+
+        Text {
+            text: "Third item on path";
+            color: black;
+        }
+
+    }
+}