feat(ui): right-edge side toolbar; drop the paper-space ribbon tab

Switching to a paper layout used to hijack the ribbon with a contextual
"Layout" tab. Replace that with a reusable right-edge vertical toolbar:
a single centred column of icon buttons floated over the canvas, built
from a flat ToolDef list and dispatching through the existing
RibbonToolClick path (ui::side_toolbar). Paper space now shows Viewport /
Page Setup / Export PDF there and leaves the ribbon on the user's tab;
the contextual layout tab and its three auto-switch hooks are removed.
The toolbar is generic infrastructure for future context action sets.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

src/ui/mod.rs

@@ -20,6 +20,7 @@ pub mod properties;
 pub mod ribbon;
 pub mod scale_popup;
 pub mod selection_filter_popup;
+pub mod side_toolbar;
 pub mod shortcuts;
 pub mod snap_popup;
 pub mod statusbar;

src/ui/ribbon/mod.rs

@@ -246,7 +246,9 @@ impl Ribbon {
                 .align_y(iced::Center)
                 .spacing(6),
             |row_acc, (i, module)| {
-                if module.id() == "layout" && !is_paper {
+                // The Layout module no longer has a ribbon tab — its paper-space
+                // tools live in the right-edge side toolbar (see ui::side_toolbar).
+                if module.id() == "layout" {
                     return row_acc;
                 }
 

src/ui/side_toolbar.rs

@@ -0,0 +1,108 @@
+//! Reusable right-edge vertical toolbar.
+//!
+//! A single centred column of icon buttons floated over the right edge of the
+//! canvas — a lightweight, context-specific alternative to a contextual ribbon
+//! tab. It is built from a flat list of [`ToolDef`]s and dispatches each tool's
+//! command through the existing [`Message::RibbonToolClick`] path, so any
+//! module's tools can drive it. First used for paper-space viewport / plot
+//! actions; reusable for any future context action set.
+
+use iced::widget::{button, column, container, svg, text, tooltip};
+use iced::{Background, Border, Color, Element, Length, Theme};
+
+use crate::app::Message;
+use crate::modules::{IconKind, ToolDef};
+
+const PANEL_BG: Color = Color { r: 0.13, g: 0.13, b: 0.13, a: 0.96 };
+const PANEL_BORDER: Color = Color { r: 0.32, g: 0.32, b: 0.32, a: 1.0 };
+const BTN_HOVER: Color = Color { r: 0.24, g: 0.24, b: 0.24, a: 1.0 };
+const ICON_SIZE: f32 = 22.0;
+const BTN_SIZE: f32 = 38.0;
+/// Gap between the toolbar and the right edge of the canvas.
+const EDGE_MARGIN: f32 = 8.0;
+
+fn icon_el(icon: IconKind) -> Element<'static, Message> {
+    match icon {
+        IconKind::Glyph(s) => text(s).size(ICON_SIZE * 0.85).color(Color::WHITE).into(),
+        IconKind::Svg(bytes) => svg(svg::Handle::from_memory(bytes))
+            .width(Length::Fixed(ICON_SIZE))
+            .height(Length::Fixed(ICON_SIZE))
+            .into(),
+    }
+}
+
+fn tip_panel(label: &'static str) -> Element<'static, Message> {
+    container(text(label).size(11).color(Color::WHITE))
+        .padding([2, 6])
+        .style(|_: &Theme| container::Style {
+            background: Some(Background::Color(PANEL_BG)),
+            border: Border {
+                color: PANEL_BORDER,
+                width: 1.0,
+                radius: 3.0.into(),
+            },
+            ..Default::default()
+        })
+        .into()
+}
+
+/// Build the floating right-edge vertical toolbar from `tools`, vertically
+/// centred over the canvas. Returns `None` when `tools` is empty so the caller
+/// can skip pushing an overlay.
+pub fn view(tools: &[ToolDef]) -> Option<Element<'static, Message>> {
+    if tools.is_empty() {
+        return None;
+    }
+
+    let mut col = column![].spacing(4).align_x(iced::Center);
+    for t in tools {
+        let btn = button(icon_el(t.icon))
+            .on_press(Message::RibbonToolClick {
+                tool_id: t.id.to_string(),
+                event: t.event.clone(),
+            })
+            .width(Length::Fixed(BTN_SIZE))
+            .height(Length::Fixed(BTN_SIZE))
+            .style(|_: &Theme, status| button::Style {
+                background: Some(Background::Color(match status {
+                    button::Status::Hovered | button::Status::Pressed => BTN_HOVER,
+                    _ => Color::TRANSPARENT,
+                })),
+                border: Border {
+                    radius: 3.0.into(),
+                    ..Default::default()
+                },
+                text_color: Color::WHITE,
+                ..Default::default()
+            });
+        // Label tooltip on the left so it never runs off the right edge.
+        col = col.push(
+            tooltip(btn, tip_panel(t.label), tooltip::Position::Left).gap(6),
+        );
+    }
+
+    let panel = container(col).padding(4).style(|_: &Theme| container::Style {
+        background: Some(Background::Color(PANEL_BG)),
+        border: Border {
+            color: PANEL_BORDER,
+            width: 1.0,
+            radius: 5.0.into(),
+        },
+        ..Default::default()
+    });
+
+    // Fill the canvas, pin the panel to the right edge and centre it
+    // vertically — no manual size/position math needed.
+    Some(
+        container(iced::widget::opaque(panel))
+            .width(Length::Fill)
+            .height(Length::Fill)
+            .align_x(iced::Right)
+            .align_y(iced::Center)
+            .padding(iced::Padding {
+                right: EDGE_MARGIN,
+                ..iced::Padding::ZERO
+            })
+            .into(),
+    )
+}