slint/sixtyfps_compiler/passes/binding_analysis.rs

/* LICENSE BEGIN
    This file is part of the SixtyFPS Project -- https://sixtyfps.io
    Copyright (c) 2021 Olivier Goffart <olivier.goffart@sixtyfps.io>
    Copyright (c) 2021 Simon Hausmann <simon.hausmann@sixtyfps.io>

    SPDX-License-Identifier: GPL-3.0-only
    This file is also available under commercial licensing terms.
    Please contact info@sixtyfps.io for more information.
LICENSE END */
//! Compute binding analysis and attempt to find binding loops

use std::rc::Rc;

use crate::diagnostics::BuildDiagnostics;
use crate::diagnostics::Spanned;
use crate::expression_tree::BindingExpression;
use crate::expression_tree::BuiltinFunction;
use crate::expression_tree::Expression;
use crate::langtype::Type;
use crate::layout::LayoutItem;
use crate::layout::Orientation;
use crate::namedreference::NamedReference;
use crate::object_tree::{Component, ElementRc};

type PropertySet = linked_hash_set::LinkedHashSet<NamedReference>;

pub fn binding_analysis(component: &Rc<Component>, diag: &mut BuildDiagnostics) {
    propagate_is_set_on_aliases(component);
    for g in component.used_types.borrow().globals.iter() {
        propagate_is_set_on_aliases(g);
    }

    crate::object_tree::recurse_elem_including_sub_components_no_borrow(
        component,
        &(),
        &mut |e, _| {
            for (name, binding) in &e.borrow().bindings {
                if matches!(e.borrow().lookup_property(name).property_type, Type::Callback { .. }) {
                    // TODO: We probably also want to do some analysis on callbacks.
                    continue;
                }
                if binding.analysis.borrow().is_some() {
                    continue;
                }
                let mut set = PropertySet::default();
                analyse_binding(e, name, &mut set, diag);
            }
        },
    );
}

fn analyse_binding(
    element: &ElementRc,
    name: &str,
    currently_analysing: &mut PropertySet,
    diag: &mut BuildDiagnostics,
) {
    let nr = NamedReference::new(element, name);
    if currently_analysing.back().map_or(false, |r| *r == nr)
        && !element.borrow().bindings[name].two_way_bindings.is_empty()
    {
        // This is already reported as an error by the remove_alias pass.
        // FIXME: maybe we should report it there instead
        return;
    }

    if currently_analysing.contains(&nr) {
        for p in currently_analysing.iter().rev() {
            let elem = p.element();
            let elem = elem.borrow();
            if std::mem::replace(
                &mut elem.bindings[p.name()]
                    .analysis
                    .borrow_mut()
                    .get_or_insert(Default::default())
                    .is_in_binding_loop,
                true,
            ) {
                break;
            }

            let span = elem.bindings[p.name()]
                .span
                .clone()
                .or_else(|| elem.node.as_ref().map(|n| n.to_source_location()));
            diag.push_error(
                format!("The binding for the property '{}' is part of a binding loop", p.name()),
                &span,
            );

            if *p == nr {
                break;
            }
        }
        return;
    }
    currently_analysing.insert(nr.clone());

    let mut process_prop = |prop: &NamedReference| {
        prop.element()
            .borrow()
            .property_analysis
            .borrow_mut()
            .entry(prop.name().into())
            .or_default()
            .is_read = true;
        if let Some(binding) = prop.element().borrow().bindings.get(prop.name()) {
            if binding.analysis.borrow().is_some() {
                return;
            }
            analyse_binding(&prop.element(), prop.name(), currently_analysing, diag);
        }
    };
    let binding = &element.borrow().bindings[name];
    for nr in &binding.two_way_bindings {
        process_prop(nr);
    }
    recurse_expression(&binding.expression, &mut process_prop);

    {
        let elem = element.borrow();
        let b = &elem.bindings[name];
        let is_const =
            b.expression.is_constant() && b.two_way_bindings.iter().all(|n| n.is_constant());

        let mut analysis = b.analysis.borrow_mut();
        let mut analysis = analysis.get_or_insert(Default::default());
        analysis.is_const = is_const;
    }

    let o = currently_analysing.pop_back();
    assert_eq!(o.unwrap(), nr);
}

// Same as in crate::visit_all_named_references_in_element, but not mut
fn recurse_expression(expr: &Expression, vis: &mut impl FnMut(&NamedReference)) {
    expr.visit(|sub| recurse_expression(sub, vis));
    match expr {
        Expression::PropertyReference(r) | Expression::CallbackReference(r) => vis(r),
        Expression::LayoutCacheAccess { layout_cache_prop, .. } => vis(layout_cache_prop),
        Expression::SolveLayout(l, o) | Expression::ComputeLayoutInfo(l, o) => {
            // we should only visit the layout geometry for the orientation
            if matches!(expr, Expression::SolveLayout(..)) {
                l.rect().size_reference(*o).map(&mut |nr| vis(nr));
            }
            match l {
                crate::layout::Layout::GridLayout(l) => {
                    visit_layout_items_dependencies(l.elems.iter().map(|it| &it.item), *o, vis)
                }
                crate::layout::Layout::BoxLayout(l) => {
                    visit_layout_items_dependencies(l.elems.iter(), *o, vis)
                }
                crate::layout::Layout::PathLayout(l) => {
                    for it in &l.elements {
                        vis(&NamedReference::new(it, "width"));
                        vis(&NamedReference::new(it, "height"));
                    }
                }
            }
            if let Some(g) = l.geometry() {
                let mut g = g.clone();
                g.rect = Default::default(); // already visited;
                g.visit_named_references(&mut |nr| vis(nr))
            }
        }
        Expression::FunctionCall { function, arguments, .. } => {
            if let Expression::BuiltinFunctionReference(
                BuiltinFunction::ImplicitLayoutInfo(orientation),
                _,
            ) = &**function
            {
                if let [Expression::ElementReference(item)] = arguments.as_slice() {
                    visit_implicit_layout_info_dependencies(
                        *orientation,
                        &item.upgrade().unwrap(),
                        vis,
                    );
                }
            }
        }
        _ => {}
    }
}

fn visit_layout_items_dependencies<'a>(
    items: impl Iterator<Item = &'a LayoutItem>,
    orientation: Orientation,
    vis: &mut impl FnMut(&NamedReference),
) {
    for it in items {
        if let Some(nr) = it.element.borrow().layout_info_prop(orientation) {
            vis(nr);
        } else {
            visit_implicit_layout_info_dependencies(orientation, &it.element, vis);
        }

        for (nr, _) in it.constraints.for_each_restrictions(orientation) {
            vis(nr)
        }
    }
}

/// The builtin function can call native code, and we need to visit the properties that are accessed by it
fn visit_implicit_layout_info_dependencies(
    orientation: crate::layout::Orientation,
    item: &ElementRc,
    vis: &mut impl FnMut(&NamedReference),
) {
    let base_type = item.borrow().base_type.to_string();
    match base_type.as_str() {
        "Image" => {
            vis(&NamedReference::new(item, "source"));
            if orientation == Orientation::Vertical {
                vis(&NamedReference::new(item, "width"));
            }
        }
        "Text" | "TextInput" => {
            vis(&NamedReference::new(item, "text"));
            vis(&NamedReference::new(item, "font-family"));
            vis(&NamedReference::new(item, "font-size"));
            vis(&NamedReference::new(item, "font-weight"));
            vis(&NamedReference::new(item, "letter-spacing"));
            vis(&NamedReference::new(item, "wrap"));
            if orientation == Orientation::Vertical {
                vis(&NamedReference::new(item, "width"));
            }
            if base_type.as_str() == "TextInput" {
                vis(&NamedReference::new(item, "single-line"));
            } else {
                vis(&NamedReference::new(item, "overflow"));
            }
        }

        _ => (),
    }
}

/// Make sure that the is_set property analysis is set to any property which has a two way binding
/// to a property that is, itself, is set
///
/// Example:
/// ```60
/// Xx := TouchArea {
///    property <int> bar <=> foo;
///    clicked => { bar+=1; }
///    property <int> foo; // must ensure that this is not considered as const, because the alias with bar
/// }
/// ```
fn propagate_is_set_on_aliases(component: &Rc<Component>) {
    crate::object_tree::recurse_elem_including_sub_components_no_borrow(
        component,
        &(),
        &mut |e, _| {
            for (name, binding) in &e.borrow().bindings {
                if !binding.two_way_bindings.is_empty() {
                    check_alias(e, name, binding);
                }
            }
        },
    );

    fn check_alias(e: &ElementRc, name: &str, binding: &BindingExpression) {
        // Note: since the analysis hasn't been run, any property access will result in a non constant binding. this is slightly non-optimal
        let is_binding_constant =
            binding.is_constant() && binding.two_way_bindings.iter().all(|n| n.is_constant());
        if is_binding_constant && !NamedReference::new(e, name).is_externally_modified() {
            return;
        }

        propagate_alias(binding);
    }

    fn propagate_alias(binding: &BindingExpression) {
        for alias in &binding.two_way_bindings {
            if !alias.is_externally_modified() {
                let al_el = alias.element();
                let al_el = al_el.borrow();
                al_el
                    .property_analysis
                    .borrow_mut()
                    .entry(alias.name().into())
                    .or_default()
                    .is_set = true;
                if let Some(bind) = al_el.bindings.get(alias.name()) {
                    propagate_alias(bind)
                }
            }
        }
    }
}