slint/internal/compiler/layout.rs

// Copyright © SixtyFPS GmbH <info@slint.dev>
// SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-Royalty-free-2.0 OR LicenseRef-Slint-Software-3.0

//! Datastructures used to represent layouts in the compiler

use crate::diagnostics::{BuildDiagnostics, DiagnosticLevel, Spanned};
use crate::expression_tree::*;
use crate::langtype::{ElementType, PropertyLookupResult, Type};
use crate::object_tree::{Component, ElementRc};

use smol_str::{format_smolstr, SmolStr, ToSmolStr};

use std::cell::RefCell;
use std::rc::{Rc, Weak};

#[derive(Clone, Debug, Copy, Eq, PartialEq)]
pub enum Orientation {
    Horizontal,
    Vertical,
}

#[derive(Clone, Debug, derive_more::From)]
pub enum Layout {
    GridLayout(GridLayout),
    BoxLayout(BoxLayout),
}

impl Layout {
    pub fn rect(&self) -> &LayoutRect {
        match self {
            Layout::GridLayout(g) => &g.geometry.rect,
            Layout::BoxLayout(g) => &g.geometry.rect,
        }
    }
    pub fn rect_mut(&mut self) -> &mut LayoutRect {
        match self {
            Layout::GridLayout(g) => &mut g.geometry.rect,
            Layout::BoxLayout(g) => &mut g.geometry.rect,
        }
    }
    pub fn geometry(&self) -> &LayoutGeometry {
        match self {
            Layout::GridLayout(l) => &l.geometry,
            Layout::BoxLayout(l) => &l.geometry,
        }
    }
}

impl Layout {
    /// Call the visitor for each NamedReference stored in the layout
    pub fn visit_named_references(&mut self, visitor: &mut impl FnMut(&mut NamedReference)) {
        match self {
            Layout::GridLayout(grid) => grid.visit_named_references(visitor),
            Layout::BoxLayout(l) => l.visit_named_references(visitor),
        }
    }
}

/// An Item in the layout tree
#[derive(Debug, Default, Clone)]
pub struct LayoutItem {
    pub element: ElementRc,
    pub constraints: LayoutConstraints,
}

impl LayoutItem {
    pub fn rect(&self) -> LayoutRect {
        let p = |unresolved_name: &str| {
            let PropertyLookupResult { resolved_name, property_type, .. } =
                self.element.borrow().lookup_property(unresolved_name);
            if property_type == Type::LogicalLength {
                Some(NamedReference::new(&self.element, resolved_name.to_smolstr()))
            } else {
                None
            }
        };
        LayoutRect {
            x_reference: p("x"),
            y_reference: p("y"),
            width_reference: if !self.constraints.fixed_width { p("width") } else { None },
            height_reference: if !self.constraints.fixed_height { p("height") } else { None },
        }
    }
}

#[derive(Debug, Clone, Default)]
pub struct LayoutRect {
    pub width_reference: Option<NamedReference>,
    pub height_reference: Option<NamedReference>,
    pub x_reference: Option<NamedReference>,
    pub y_reference: Option<NamedReference>,
}

impl LayoutRect {
    pub fn install_on_element(element: &ElementRc) -> Self {
        let install_prop =
            |name: &'static str| Some(NamedReference::new(element, SmolStr::new_static(name)));

        Self {
            x_reference: install_prop("x"),
            y_reference: install_prop("y"),
            width_reference: install_prop("width"),
            height_reference: install_prop("height"),
        }
    }

    fn visit_named_references(&mut self, mut visitor: &mut impl FnMut(&mut NamedReference)) {
        self.width_reference.as_mut().map(&mut visitor);
        self.height_reference.as_mut().map(&mut visitor);
        self.x_reference.as_mut().map(&mut visitor);
        self.y_reference.as_mut().map(&mut visitor);
    }

    pub fn size_reference(&self, orientation: Orientation) -> Option<&NamedReference> {
        match orientation {
            Orientation::Horizontal => self.width_reference.as_ref(),
            Orientation::Vertical => self.height_reference.as_ref(),
        }
    }
}

#[derive(Debug, Default, Clone)]
pub struct LayoutConstraints {
    pub min_width: Option<NamedReference>,
    pub max_width: Option<NamedReference>,
    pub min_height: Option<NamedReference>,
    pub max_height: Option<NamedReference>,
    pub preferred_width: Option<NamedReference>,
    pub preferred_height: Option<NamedReference>,
    pub horizontal_stretch: Option<NamedReference>,
    pub vertical_stretch: Option<NamedReference>,
    pub fixed_width: bool,
    pub fixed_height: bool,
}

impl LayoutConstraints {
    /// Build the constraints for the given element
    ///
    /// Report diagnostics when both constraints and fixed size are set
    /// (one can set the level to warning to keep compatibility to old version of Slint)
    pub fn new(element: &ElementRc, diag: &mut BuildDiagnostics, level: DiagnosticLevel) -> Self {
        let mut constraints = Self {
            min_width: binding_reference(element, "min-width"),
            max_width: binding_reference(element, "max-width"),
            min_height: binding_reference(element, "min-height"),
            max_height: binding_reference(element, "max-height"),
            preferred_width: binding_reference(element, "preferred-width"),
            preferred_height: binding_reference(element, "preferred-height"),
            horizontal_stretch: binding_reference(element, "horizontal-stretch"),
            vertical_stretch: binding_reference(element, "vertical-stretch"),
            fixed_width: false,
            fixed_height: false,
        };
        let mut apply_size_constraint =
            |prop: &'static str,
             binding: &BindingExpression,
             enclosing1: &Weak<Component>,
             depth,
             op: &mut Option<NamedReference>| {
                if let Some(other_prop) = op {
                    find_binding(
                        &other_prop.element(),
                        other_prop.name(),
                        |old, enclosing2, d2| {
                            if Weak::ptr_eq(enclosing1, enclosing2)
                                && old.priority.saturating_add(d2)
                                    <= binding.priority.saturating_add(depth)
                            {
                                diag.push_diagnostic_with_span(
                                    format!(
                                        "Cannot specify both '{prop}' and '{}'",
                                        other_prop.name()
                                    ),
                                    binding.to_source_location(),
                                    level,
                                );
                            }
                        },
                    );
                }
                *op = Some(NamedReference::new(element, SmolStr::new_static(prop)))
            };
        find_binding(element, "height", |s, enclosing, depth| {
            constraints.fixed_height = true;
            apply_size_constraint("height", s, enclosing, depth, &mut constraints.min_height);
            apply_size_constraint("height", s, enclosing, depth, &mut constraints.max_height);
        });
        find_binding(element, "width", |s, enclosing, depth| {
            constraints.fixed_width = true;
            if s.expression.ty() == Type::Percent {
                apply_size_constraint("width", s, enclosing, depth, &mut constraints.min_width);
            } else {
                apply_size_constraint("width", s, enclosing, depth, &mut constraints.min_width);
                apply_size_constraint("width", s, enclosing, depth, &mut constraints.max_width);
            }
        });

        constraints
    }

    pub fn has_explicit_restrictions(&self, orientation: Orientation) -> bool {
        match orientation {
            Orientation::Horizontal => {
                self.min_width.is_some()
                    || self.max_width.is_some()
                    || self.preferred_width.is_some()
                    || self.horizontal_stretch.is_some()
            }
            Orientation::Vertical => {
                self.min_height.is_some()
                    || self.max_height.is_some()
                    || self.preferred_height.is_some()
                    || self.vertical_stretch.is_some()
            }
        }
    }

    // Iterate over the constraint with a reference to a property, and the corresponding member in the i_slint_core::layout::LayoutInfo struct
    pub fn for_each_restrictions(
        &self,
        orientation: Orientation,
    ) -> impl Iterator<Item = (&NamedReference, &'static str)> {
        let (min, max, preferred, stretch) = match orientation {
            Orientation::Horizontal => {
                (&self.min_width, &self.max_width, &self.preferred_width, &self.horizontal_stretch)
            }
            Orientation::Vertical => {
                (&self.min_height, &self.max_height, &self.preferred_height, &self.vertical_stretch)
            }
        };
        std::iter::empty()
            .chain(min.as_ref().map(|x| {
                if Expression::PropertyReference(x.clone()).ty() != Type::Percent {
                    (x, "min")
                } else {
                    (x, "min_percent")
                }
            }))
            .chain(max.as_ref().map(|x| {
                if Expression::PropertyReference(x.clone()).ty() != Type::Percent {
                    (x, "max")
                } else {
                    (x, "max_percent")
                }
            }))
            .chain(preferred.as_ref().map(|x| (x, "preferred")))
            .chain(stretch.as_ref().map(|x| (x, "stretch")))
    }

    pub fn visit_named_references(&mut self, visitor: &mut impl FnMut(&mut NamedReference)) {
        if let Some(e) = self.max_width.as_mut() {
            visitor(&mut *e);
        }
        if let Some(e) = self.min_width.as_mut() {
            visitor(&mut *e);
        }
        if let Some(e) = self.max_height.as_mut() {
            visitor(&mut *e);
        }
        if let Some(e) = self.min_height.as_mut() {
            visitor(&mut *e);
        }
        if let Some(e) = self.preferred_width.as_mut() {
            visitor(&mut *e);
        }
        if let Some(e) = self.preferred_height.as_mut() {
            visitor(&mut *e);
        }
        if let Some(e) = self.horizontal_stretch.as_mut() {
            visitor(&mut *e);
        }
        if let Some(e) = self.vertical_stretch.as_mut() {
            visitor(&mut *e);
        }
    }
}

/// An element in a GridLayout
#[derive(Debug, Clone)]
pub struct GridLayoutElement {
    pub col: u16,
    pub row: u16,
    pub colspan: u16,
    pub rowspan: u16,
    pub item: LayoutItem,
}

impl GridLayoutElement {
    pub fn col_or_row_and_span(&self, orientation: Orientation) -> (u16, u16) {
        match orientation {
            Orientation::Horizontal => (self.col, self.colspan),
            Orientation::Vertical => (self.row, self.rowspan),
        }
    }
}

#[derive(Debug, Clone)]
pub struct Padding {
    pub left: Option<NamedReference>,
    pub right: Option<NamedReference>,
    pub top: Option<NamedReference>,
    pub bottom: Option<NamedReference>,
}

impl Padding {
    fn visit_named_references(&mut self, visitor: &mut impl FnMut(&mut NamedReference)) {
        if let Some(e) = self.left.as_mut() {
            visitor(&mut *e)
        }
        if let Some(e) = self.right.as_mut() {
            visitor(&mut *e)
        }
        if let Some(e) = self.top.as_mut() {
            visitor(&mut *e)
        }
        if let Some(e) = self.bottom.as_mut() {
            visitor(&mut *e)
        }
    }

    // Return reference to the begin and end padding for a given orientation
    pub fn begin_end(&self, o: Orientation) -> (Option<&NamedReference>, Option<&NamedReference>) {
        match o {
            Orientation::Horizontal => (self.left.as_ref(), self.right.as_ref()),
            Orientation::Vertical => (self.top.as_ref(), self.bottom.as_ref()),
        }
    }
}

#[derive(Debug, Clone)]
pub struct Spacing {
    pub horizontal: Option<NamedReference>,
    pub vertical: Option<NamedReference>,
}

impl Spacing {
    fn visit_named_references(&mut self, visitor: &mut impl FnMut(&mut NamedReference)) {
        if let Some(e) = self.horizontal.as_mut() {
            visitor(&mut *e);
        }
        if let Some(e) = self.vertical.as_mut() {
            visitor(&mut *e);
        }
    }

    pub fn orientation(&self, o: Orientation) -> Option<&NamedReference> {
        match o {
            Orientation::Horizontal => self.horizontal.as_ref(),
            Orientation::Vertical => self.vertical.as_ref(),
        }
    }
}

#[derive(Debug, Clone)]
pub struct LayoutGeometry {
    pub rect: LayoutRect,
    pub spacing: Spacing,
    pub alignment: Option<NamedReference>,
    pub padding: Padding,
}

impl LayoutGeometry {
    pub fn visit_named_references(&mut self, visitor: &mut impl FnMut(&mut NamedReference)) {
        self.rect.visit_named_references(visitor);
        if let Some(e) = self.alignment.as_mut() {
            visitor(&mut *e)
        }
        self.spacing.visit_named_references(visitor);
        self.padding.visit_named_references(visitor);
    }

    pub fn new(layout_element: &ElementRc) -> Self {
        let spacing = || binding_reference(layout_element, "spacing");
        init_fake_property(layout_element, "spacing-horizontal", spacing);
        init_fake_property(layout_element, "spacing-vertical", spacing);

        let alignment = binding_reference(layout_element, "alignment");

        let padding = || binding_reference(layout_element, "padding");
        init_fake_property(layout_element, "padding-left", padding);
        init_fake_property(layout_element, "padding-right", padding);
        init_fake_property(layout_element, "padding-top", padding);
        init_fake_property(layout_element, "padding-bottom", padding);

        let padding = Padding {
            left: binding_reference(layout_element, "padding-left").or_else(padding),
            right: binding_reference(layout_element, "padding-right").or_else(padding),
            top: binding_reference(layout_element, "padding-top").or_else(padding),
            bottom: binding_reference(layout_element, "padding-bottom").or_else(padding),
        };

        let spacing = Spacing {
            horizontal: binding_reference(layout_element, "spacing-horizontal").or_else(spacing),
            vertical: binding_reference(layout_element, "spacing-vertical").or_else(spacing),
        };

        let rect = LayoutRect::install_on_element(layout_element);

        Self { rect, spacing, padding, alignment }
    }
}

/// If this element or any of the parent has a binding to the property, call the functor with that binding, and the depth.
/// Return None if the binding does not exist in any of the sub component, or Some with the result of the functor otherwise
fn find_binding<R>(
    element: &ElementRc,
    name: &str,
    f: impl FnOnce(&BindingExpression, &Weak<Component>, i32) -> R,
) -> Option<R> {
    let mut element = element.clone();
    let mut depth = 0;
    loop {
        if let Some(b) = element.borrow().bindings.get(name) {
            if b.borrow().has_binding() {
                return Some(f(&b.borrow(), &element.borrow().enclosing_component, depth));
            }
        }
        let e = match &element.borrow().base_type {
            ElementType::Component(base) => base.root_element.clone(),
            _ => return None,
        };
        element = e;
        depth += 1;
    }
}

/// Return a named reference to a property if a binding is set on that property
fn binding_reference(element: &ElementRc, name: &'static str) -> Option<NamedReference> {
    find_binding(element, name, |_, _, _| NamedReference::new(element, SmolStr::new_static(name)))
}

fn init_fake_property(
    grid_layout_element: &ElementRc,
    name: &str,
    lazy_default: impl Fn() -> Option<NamedReference>,
) {
    if grid_layout_element.borrow().property_declarations.contains_key(name)
        && !grid_layout_element.borrow().bindings.contains_key(name)
    {
        if let Some(e) = lazy_default() {
            if e.name() == name && Rc::ptr_eq(&e.element(), grid_layout_element) {
                // Don't reference self
                return;
            }
            grid_layout_element
                .borrow_mut()
                .bindings
                .insert(name.into(), RefCell::new(Expression::PropertyReference(e).into()));
        }
    }
}

/// Internal representation of a grid layout
#[derive(Debug, Clone)]
pub struct GridLayout {
    /// All the elements will be layout within that element.
    pub elems: Vec<GridLayoutElement>,

    pub geometry: LayoutGeometry,

    /// When this GridLayout is actually the layout of a Dialog, then the cells start with all the buttons,
    /// and this variable contains their roles. The string is actually one of the values from the i_slint_core::layout::DialogButtonRole
    pub dialog_button_roles: Option<Vec<SmolStr>>,
}

impl GridLayout {
    fn visit_named_references(&mut self, visitor: &mut impl FnMut(&mut NamedReference)) {
        for cell in &mut self.elems {
            cell.item.constraints.visit_named_references(visitor);
        }
        self.geometry.visit_named_references(visitor);
    }
}

/// Internal representation of a BoxLayout
#[derive(Debug, Clone)]
pub struct BoxLayout {
    /// Whether, this is a HorizontalLayout, otherwise a VerticalLayout
    pub orientation: Orientation,
    pub elems: Vec<LayoutItem>,
    pub geometry: LayoutGeometry,
}

impl BoxLayout {
    fn visit_named_references(&mut self, visitor: &mut impl FnMut(&mut NamedReference)) {
        for cell in &mut self.elems {
            cell.constraints.visit_named_references(visitor);
        }
        self.geometry.visit_named_references(visitor);
    }
}

/// Get the implicit layout info of a particular element
pub fn implicit_layout_info_call(elem: &ElementRc, orientation: Orientation) -> Expression {
    let mut elem_it = elem.clone();
    loop {
        return match &elem_it.clone().borrow().base_type {
            ElementType::Component(base_comp) => {
                match base_comp.root_element.borrow().layout_info_prop(orientation) {
                    Some(nr) => {
                        // We cannot take nr as is because it is relative to the elem's component. We therefore need to
                        // use `elem` as an element for the PropertyReference, not `root` within the base of elem
                        debug_assert!(Rc::ptr_eq(&nr.element(), &base_comp.root_element));
                        Expression::PropertyReference(NamedReference::new(elem, nr.name().clone()))
                    }
                    None => {
                        elem_it = base_comp.root_element.clone();
                        continue;
                    }
                }
            }
            ElementType::Builtin(base_type)
                if matches!(
                    base_type.name.as_str(),
                    "Rectangle"
                        | "Empty"
                        | "TouchArea"
                        | "FocusScope"
                        | "Opacity"
                        | "Layer"
                        | "BoxShadow"
                        | "Clip"
                ) =>
            {
                // hard-code the value for rectangle because many rectangle end up optimized away and we
                // don't want to depend on the element.
                Expression::Struct {
                    ty: crate::typeregister::layout_info_type(),
                    values: [("min", 0.), ("max", f32::MAX), ("preferred", 0.)]
                        .iter()
                        .map(|(s, v)| {
                            (SmolStr::new_static(s), Expression::NumberLiteral(*v as _, Unit::Px))
                        })
                        .chain(
                            [("min_percent", 0.), ("max_percent", 100.), ("stretch", 1.)]
                                .iter()
                                .map(|(s, v)| {
                                    (
                                        SmolStr::new_static(s),
                                        Expression::NumberLiteral(*v, Unit::None),
                                    )
                                }),
                        )
                        .collect(),
                }
            }
            _ => Expression::FunctionCall {
                function: BuiltinFunction::ImplicitLayoutInfo(orientation).into(),
                arguments: vec![Expression::ElementReference(Rc::downgrade(elem))],
                source_location: None,
            },
        };
    }
}

/// Create a new property based on the name. (it might get a different name if that property exist)
pub fn create_new_prop(elem: &ElementRc, tentative_name: SmolStr, ty: Type) -> NamedReference {
    let mut e = elem.borrow_mut();
    if !e.lookup_property(&tentative_name).is_valid() {
        e.property_declarations.insert(tentative_name.clone(), ty.into());
        drop(e);
        NamedReference::new(elem, tentative_name)
    } else {
        let mut counter = 0;
        loop {
            counter += 1;
            let name = format_smolstr!("{}{}", tentative_name, counter);
            if !e.lookup_property(&name).is_valid() {
                e.property_declarations.insert(name.clone(), ty.into());
                drop(e);
                return NamedReference::new(elem, name);
            }
        }
    }
}

/// Return true if this type is a layout that has constraints
pub fn is_layout(base_type: &ElementType) -> bool {
    match base_type {
        ElementType::Component(c) => is_layout(&c.root_element.borrow().base_type),
        ElementType::Builtin(be) => {
            matches!(be.name.as_str(), "GridLayout" | "HorizontalLayout" | "VerticalLayout")
        }
        _ => false,
    }
}