i_slint_compiler/passes/
remove_aliases.rs

1// Copyright © SixtyFPS GmbH <info@slint.dev>
2// SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-Royalty-free-2.0 OR LicenseRef-Slint-Software-3.0
3
4//! This pass removes the property used in a two ways bindings
5
6use crate::diagnostics::BuildDiagnostics;
7use crate::expression_tree::{BindingExpression, Expression, NamedReference};
8use crate::object_tree::*;
9use std::cell::RefCell;
10use std::collections::{btree_map::Entry, HashMap, HashSet};
11use std::rc::Rc;
12
13// The property in the key is to be removed, and replaced by the property in the value
14type Mapping = HashMap<NamedReference, NamedReference>;
15
16#[derive(Default, Debug)]
17struct PropertySets {
18    map: HashMap<NamedReference, Rc<RefCell<HashSet<NamedReference>>>>,
19    all_sets: Vec<Rc<RefCell<HashSet<NamedReference>>>>,
20}
21
22impl PropertySets {
23    fn add_link(&mut self, p1: NamedReference, p2: NamedReference) {
24        let (e1, e2) = (p1.element(), p2.element());
25        if !std::rc::Weak::ptr_eq(
26            &e1.borrow().enclosing_component,
27            &e2.borrow().enclosing_component,
28        ) {
29            if !(e1.borrow().enclosing_component.upgrade().unwrap().is_global()
30                && !e2.borrow().change_callbacks.contains_key(p2.name()))
31                && !(e2.borrow().enclosing_component.upgrade().unwrap().is_global()
32                    && !e1.borrow().change_callbacks.contains_key(p1.name()))
33            {
34                // We can only merge aliases if they are in the same Component. (unless one of them is global if the other one don't have change event)
35                // TODO: actually we could still merge two alias in a component pointing to the same
36                // property in a parent component
37                return;
38            }
39        }
40
41        if let Some(s1) = self.map.get(&p1).cloned() {
42            if let Some(s2) = self.map.get(&p2).cloned() {
43                if Rc::ptr_eq(&s1, &s2) {
44                    return;
45                }
46                for x in s1.borrow().iter() {
47                    self.map.insert(x.clone(), s2.clone());
48                    s2.borrow_mut().insert(x.clone());
49                }
50                *s1.borrow_mut() = HashSet::new();
51            } else {
52                s1.borrow_mut().insert(p2.clone());
53                self.map.insert(p2, s1);
54            }
55        } else if let Some(s2) = self.map.get(&p2).cloned() {
56            s2.borrow_mut().insert(p1.clone());
57            self.map.insert(p1, s2);
58        } else {
59            let mut set = HashSet::new();
60            set.insert(p1.clone());
61            set.insert(p2.clone());
62            let set = Rc::new(RefCell::new(set));
63            self.map.insert(p1, set.clone());
64            self.map.insert(p2, set.clone());
65            self.all_sets.push(set)
66        }
67    }
68}
69
70pub fn remove_aliases(doc: &Document, diag: &mut BuildDiagnostics) {
71    // collect all sets that are linked together
72    let mut property_sets = PropertySets::default();
73
74    let mut process_element = |e: &ElementRc| {
75        'bindings: for (name, binding) in &e.borrow().bindings {
76            for nr in &binding.borrow().two_way_bindings {
77                let other_e = nr.element();
78                if name == nr.name() && Rc::ptr_eq(e, &other_e) {
79                    diag.push_error("Property cannot alias to itself".into(), &*binding.borrow());
80                    continue 'bindings;
81                }
82                property_sets.add_link(NamedReference::new(e, name.clone()), nr.clone());
83            }
84        }
85    };
86
87    doc.visit_all_used_components(|component| {
88        recurse_elem_including_sub_components(component, &(), &mut |e, &()| process_element(e))
89    });
90
91    // The key will be removed and replaced by the named reference
92    let mut aliases_to_remove = Mapping::new();
93
94    // For each set, find a "master" property. Only reference to this master property will be kept,
95    // and only the master property will keep its binding
96    for set in property_sets.all_sets {
97        let set = set.borrow();
98        let mut set_iter = set.iter();
99        if let Some(mut best) = set_iter.next().cloned() {
100            for candidate in set_iter {
101                best = best_property(best.clone(), candidate.clone());
102            }
103            for x in set.iter() {
104                if *x != best {
105                    aliases_to_remove.insert(x.clone(), best.clone());
106                }
107            }
108        }
109    }
110
111    doc.visit_all_used_components(|component| {
112        // Do the replacements
113        visit_all_named_references(component, &mut |nr: &mut NamedReference| {
114            if let Some(new) = aliases_to_remove.get(nr) {
115                *nr = new.clone();
116            }
117        })
118    });
119
120    // Remove the properties
121    for (remove, to) in aliases_to_remove {
122        let elem = remove.element();
123        let to_elem = to.element();
124
125        // adjust the bindings
126        let old_binding = elem.borrow_mut().bindings.remove(remove.name());
127        let mut old_binding = old_binding.map(RefCell::into_inner).unwrap_or_else(|| {
128            // ensure that we set an expression, because the right hand side of a binding always wins,
129            // and if that was not set, we must still kee the default then
130            let mut b = BindingExpression::from(Expression::default_value_for_type(&to.ty()));
131            b.priority = to_elem
132                .borrow_mut()
133                .bindings
134                .get(to.name())
135                .map_or(i32::MAX, |x| x.borrow().priority.saturating_add(1));
136            b
137        });
138
139        remove_from_binding_expression(&mut old_binding, &to);
140
141        let same_component = std::rc::Weak::ptr_eq(
142            &elem.borrow().enclosing_component,
143            &to_elem.borrow().enclosing_component,
144        );
145        match to_elem.borrow_mut().bindings.entry(to.name().clone()) {
146            Entry::Occupied(mut e) => {
147                let b = e.get_mut().get_mut();
148                remove_from_binding_expression(b, &to);
149                if !same_component || b.priority < old_binding.priority || !b.has_binding() {
150                    b.merge_with(&old_binding);
151                } else {
152                    old_binding.merge_with(b);
153                    *b = old_binding;
154                }
155            }
156            Entry::Vacant(e) => {
157                if same_component && old_binding.has_binding() {
158                    e.insert(old_binding.into());
159                }
160            }
161        };
162
163        // Adjust the change callbacks
164        {
165            let mut elem = elem.borrow_mut();
166            if let Some(old_change_callback) = elem.change_callbacks.remove(remove.name()) {
167                drop(elem);
168                let mut old_change_callback = old_change_callback.into_inner();
169                to_elem
170                    .borrow_mut()
171                    .change_callbacks
172                    .entry(to.name().clone())
173                    .or_default()
174                    .borrow_mut()
175                    .append(&mut old_change_callback);
176            }
177        }
178
179        // Remove the declaration
180        {
181            let mut elem = elem.borrow_mut();
182            let used_externally = elem
183                .property_analysis
184                .borrow()
185                .get(remove.name())
186                .is_some_and(|v| v.is_read_externally || v.is_set_externally);
187            if let Some(d) = elem.property_declarations.get_mut(remove.name()) {
188                if d.expose_in_public_api || used_externally {
189                    d.is_alias = Some(to.clone());
190                    drop(elem);
191                    // one must mark the aliased property as settable from outside
192                    to.mark_as_set();
193                } else {
194                    elem.property_declarations.remove(remove.name());
195                    let analysis = elem.property_analysis.borrow().get(remove.name()).cloned();
196                    if let Some(analysis) = analysis {
197                        drop(elem);
198                        to.element()
199                            .borrow()
200                            .property_analysis
201                            .borrow_mut()
202                            .entry(to.name().clone())
203                            .or_default()
204                            .merge(&analysis);
205                    };
206                }
207            } else {
208                // This is not a declaration, we must re-create the binding
209                elem.bindings.insert(
210                    remove.name().clone(),
211                    BindingExpression::new_two_way(to.clone()).into(),
212                );
213                drop(elem);
214                if remove.is_externally_modified() {
215                    to.mark_as_set();
216                }
217            }
218        }
219    }
220}
221
222fn is_declaration(x: &NamedReference) -> bool {
223    x.element().borrow().property_declarations.contains_key(x.name())
224}
225
226/// Out of two named reference, return the one which is the best to keep.
227fn best_property(p1: NamedReference, p2: NamedReference) -> NamedReference {
228    // Try to find which is the more canonical property
229    macro_rules! canonical_order {
230        ($x: expr) => {{
231            (
232                !$x.element().borrow().enclosing_component.upgrade().unwrap().is_global(),
233                is_declaration(&$x),
234                $x.element().borrow().id.clone(),
235                $x.name(),
236            )
237        }};
238    }
239
240    if canonical_order!(p1) < canonical_order!(p2) {
241        p1
242    } else {
243        p2
244    }
245}
246
247/// Remove the `to` from the two_way_bindings
248fn remove_from_binding_expression(expression: &mut BindingExpression, to: &NamedReference) {
249    expression.two_way_bindings.retain(|x| x != to);
250}
i_slint_compiler/passes/remove_aliases.rs

i_slint_compiler/passes/
remove_aliases.rs
