Robius Widget Patterns

Standard Widget Structure

use makepad_widgets::*;

live_design! {
    use link::theme::*;
    use link::widgets::*;

    pub MyWidget = {{MyWidget}} {
        width: Fill, height: Fit,
        flow: Down,

        // Child widgets defined in DSL
        inner_view = <View> {
            // ...
        }
    }
}

#[derive(Live, LiveHook, Widget)]
pub struct MyWidget {
    #[deref] view: View,              // Delegate to inner View

    #[live] some_property: f64,       // DSL-configurable property
    #[live(100.0)] default_val: f64,  // With default value

    #[rust] internal_state: State,    // Rust-only state (not in DSL)

    #[animator] animator: Animator,   // For animations
}

impl Widget for MyWidget {
    fn handle_event(&mut self, cx: &mut Cx, event: &Event, scope: &mut Scope) {
        self.view.handle_event(cx, event, scope);
        // Custom event handling...
    }

    fn draw_walk(&mut self, cx: &mut Cx2d, scope: &mut Scope, walk: Walk) -> DrawStep {
        self.view.draw_walk(cx, scope, walk)
    }
}

Text/Image Toggle Pattern

A common pattern for widgets that show either text or an image (like avatars):

live_design! {
    pub Avatar = {{Avatar}} {
        width: 36.0, height: 36.0,
        align: { x: 0.5, y: 0.5 }
        flow: Overlay,  // Stack views on top of each other

        text_view = <View> {
            visible: true,  // Default visible
            show_bg: true,
            draw_bg: {
                uniform background_color: #888888
                fn pixel(self) -> vec4 {
                    let sdf = Sdf2d::viewport(self.pos * self.rect_size);
                    let c = self.rect_size * 0.5;
                    sdf.circle(c.x, c.x, c.x)
                    sdf.fill_keep(self.background_color);
                    return sdf.result
                }
            }
            text = <Label> {
                text: "?"
            }
        }

        img_view = <View> {
            visible: false,  // Hidden by default
            img = <Image> {
                fit: Stretch,
                width: Fill, height: Fill,
            }
        }
    }
}

#[derive(LiveHook, Live, Widget)]
pub struct Avatar {
    #[deref] view: View,
    #[rust] info: Option<UserInfo>,
}

impl Avatar {
    /// Show text content, hiding the image
    pub fn show_text<T: AsRef<str>>(
        &mut self,
        cx: &mut Cx,
        bg_color: Option<Vec4>,
        info: Option<AvatarTextInfo>,
        username: T,
    ) {
        self.info = info.map(|i| i.into());

        // Get first character
        let first_char = utils::first_letter(username.as_ref())
            .unwrap_or("?").to_uppercase();
        self.label(ids!(text_view.text)).set_text(cx, &first_char);

        // Toggle visibility
        self.view(ids!(text_view)).set_visible(cx, true);
        self.view(ids!(img_view)).set_visible(cx, false);

        // Apply optional background color
        if let Some(color) = bg_color {
            self.view(ids!(text_view)).apply_over(cx, live! {
                draw_bg: { background_color: (color) }
            });
        }
    }

    /// Show image content, hiding the text
    pub fn show_image<F, E>(
        &mut self,
        cx: &mut Cx,
        info: Option<AvatarImageInfo>,
        image_set_fn: F,
    ) -> Result<(), E>
    where
        F: FnOnce(&mut Cx, ImageRef) -> Result<(), E>
    {
        let img_ref = self.image(ids!(img_view.img));
        let res = image_set_fn(cx, img_ref);

        if res.is_ok() {
            self.view(ids!(img_view)).set_visible(cx, true);
            self.view(ids!(text_view)).set_visible(cx, false);
            self.info = info.map(|i| i.into());
        }
        res
    }

    /// Check current display status
    pub fn status(&mut self) -> DisplayStatus {
        if self.view(ids!(img_view)).visible() {
            DisplayStatus::Image
        } else {
            DisplayStatus::Text
        }
    }
}

Dynamic Styling with apply_over

Apply dynamic styles at runtime:

// Apply single property
self.view(ids!(content)).apply_over(cx, live! {
    draw_bg: { color: #ff0000 }
});

// Apply multiple properties
self.view(ids!(message)).apply_over(cx, live! {
    padding: { left: 20, right: 20 }
    margin: { top: 10 }
});

// Apply with variables
let highlight_color = if is_selected { vec4(1.0, 0.0, 0.0, 1.0) } else { vec4(0.5, 0.5, 0.5, 1.0) };
self.view(ids!(item)).apply_over(cx, live! {
    draw_bg: { color: (highlight_color) }
});

Widget Reference Pattern

Implement *Ref methods for external API:

impl AvatarRef {
    /// See [`Avatar::show_text()`].
    pub fn show_text<T: AsRef<str>>(
        &self,
        cx: &mut Cx,
        bg_color: Option<Vec4>,
        info: Option<AvatarTextInfo>,
        username: T,
    ) {
        if let Some(mut inner) = self.borrow_mut() {
            inner.show_text(cx, bg_color, info, username);
        }
    }

    /// See [`Avatar::show_image()`].
    pub fn show_image<F, E>(
        &self,
        cx: &mut Cx,
        info: Option<AvatarImageInfo>,
        image_set_fn: F,
    ) -> Result<(), E>
    where
        F: FnOnce(&mut Cx, ImageRef) -> Result<(), E>
    {
        if let Some(mut inner) = self.borrow_mut() {
            inner.show_image(cx, info, image_set_fn)
        } else {
            Ok(())
        }
    }
}

Collapsible/Expandable Pattern

live_design! {
    pub CollapsibleSection = {{CollapsibleSection}} {
        flow: Down,

        header = <View> {
            cursor: Hand,
            icon = <Icon> { }
            title = <Label> { text: "Section" }
        }

        content = <View> {
            visible: false,
            // Expandable content here
        }
    }
}

#[derive(Live, LiveHook, Widget)]
pub struct CollapsibleSection {
    #[deref] view: View,
    #[rust] is_expanded: bool,
}

impl CollapsibleSection {
    pub fn toggle(&mut self, cx: &mut Cx) {
        self.is_expanded = !self.is_expanded;
        self.view(ids!(content)).set_visible(cx, self.is_expanded);

        // Rotate icon
        let rotation = if self.is_expanded { 90.0 } else { 0.0 };
        self.view(ids!(header.icon)).apply_over(cx, live! {
            draw_icon: { rotation: (rotation) }
        });

        self.redraw(cx);
    }
}

Loading State Pattern

live_design! {
    pub LoadableContent = {{LoadableContent}} {
        flow: Overlay,

        content = <View> {
            visible: true,
            // Main content
        }

        loading_overlay = <View> {
            visible: false,
            show_bg: true,
            draw_bg: { color: #00000088 }
            align: { x: 0.5, y: 0.5 }
            <BouncingDots> { }
        }

        error_view = <View> {
            visible: false,
            error_label = <Label> { }
        }
    }
}

#[derive(Live, LiveHook, Widget)]
pub struct LoadableContent {
    #[deref] view: View,
    #[rust] state: LoadingState,
}

pub enum LoadingState {
    Idle,
    Loading,
    Loaded,
    Error(String),
}

impl LoadableContent {
    pub fn set_state(&mut self, cx: &mut Cx, state: LoadingState) {
        self.state = state;
        match &self.state {
            LoadingState::Idle | LoadingState::Loaded => {
                self.view(ids!(content)).set_visible(cx, true);
                self.view(ids!(loading_overlay)).set_visible(cx, false);
                self.view(ids!(error_view)).set_visible(cx, false);
            }
            LoadingState::Loading => {
                self.view(ids!(content)).set_visible(cx, true);
                self.view(ids!(loading_overlay)).set_visible(cx, true);
                self.view(ids!(error_view)).set_visible(cx, false);
            }
            LoadingState::Error(msg) => {
                self.view(ids!(content)).set_visible(cx, false);
                self.view(ids!(loading_overlay)).set_visible(cx, false);
                self.view(ids!(error_view)).set_visible(cx, true);
                self.label(ids!(error_view.error_label)).set_text(cx, msg);
            }
        }
        self.redraw(cx);
    }
}

PortalList Item Pattern

For virtual list items:

live_design! {
    pub ItemsList = {{ItemsList}} {
        list = <PortalList> {
            keep_invisible: false,
            auto_tail: false,
            width: Fill, height: Fill,
            flow: Down,

            // Item templates
            item_entry = <ItemEntry> {}
            header = <SectionHeader> {}
            empty = <View> {}
        }
    }
}

impl Widget for ItemsList {
    fn draw_walk(&mut self, cx: &mut Cx2d, scope: &mut Scope, walk: Walk) -> DrawStep {
        while let Some(item) = self.view.draw_walk(cx, scope, walk).step() {
            if let Some(mut list) = item.as_portal_list().borrow_mut() {
                list.set_item_range(cx, 0, self.items.len());

                while let Some(item_id) = list.next_visible_item(cx) {
                    let item = list.item(cx, item_id, live_id!(item_entry));
                    // Populate item with data
                    self.populate_item(cx, item, &self.items[item_id]);
                    item.draw_all(cx, scope);
                }
            }
        }
        DrawStep::done()
    }
}

Best Practices

1. Use #[deref] for delegation: Delegate to inner View for standard behavior
2. Separate DSL properties (#[live]) from Rust state (#[rust])
3. Implement both inner methods and *Ref wrappers
4. Use apply_over for dynamic runtime styling
5. Use flow: Overlay for toggle/swap patterns
6. Use set_visible() to toggle between alternative views
7. Always call redraw(cx) after state changes

Reference Files

• references/widget-patterns.md - Additional widget patterns (Robrix)
• references/styling-patterns.md - Dynamic styling patterns (Robrix)
• references/moly-widget-patterns.md - Moly-specific patterns
  • Slot widget for runtime content replacement
  • MolyRoot conditional rendering wrapper
  • AdaptiveView for responsive Mobile/Desktop layouts
  • Chat line variants (UserLine, BotLine, ErrorLine, etc.)
  • CommandTextInput with action buttons
  • Sidebar navigation with radio buttons

Limitations

• Use this skill only when the task clearly matches the scope described above.
• Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
• Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.