feat(paper): render-mode picker + ViewCube on active viewport

Paper-space'de bir viewport'a çift tıklanıp aktif hale gelince, model
space'deki gibi sol üst köşede render-mode dropdown'ı ve sağ üst köşede
ViewCube gösteriliyor.

- render_mode_picker helper'a çıkarıldı; model space ve aktif paper
  viewport ortak kullanıyor (kod tekrarı yok)
- SetRenderMode artık viewport-aware: aktif viewport varsa o viewport
  entity'sinin render_mode'unu, yoksa model-layout tab stilini günceller
  (Scene::active_viewport_render_mode getter/setter)
- build_viewport_primitive'e show_viewcube parametresi; aktif viewport
  primitive'i ViewCube gizmo'sunu çiziyor
- PaperViewportPane shader::Program artık Message'a özelleşti ve sol
  tık ViewCube hit-test'ini bounds-relative yapıp ViewCubeSnap üretiyor

Bilinen sorun: picker/viewcube doğru konumda görünüyor ancak tıklamalar
üstteki viewport_mouse mouse_area katmanına gidiyor; katman sırası bir
sonraki adımda düzeltilecek.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/app/update.rs

@@ -669,12 +669,6 @@ impl OpenCADStudio {
             Message::SetRenderMode(mode) => {
                 use acadrust::entities::ViewportRenderMode as M;
                 let i = self.active_tab;
-                self.tabs[i].render_mode = mode;
-                // Keep the legacy `wireframe` bool synced — both wireframe
-                // modes set it, everything else clears it.
-                let wf = matches!(mode, M::Wireframe2D | M::Wireframe3D);
-                self.tabs[i].wireframe = wf;
-                self.ribbon.set_wireframe(wf);
                 let label = match mode {
                     M::Wireframe2D => "Wireframe 2D",
                     M::Wireframe3D => "Wireframe 3D",
@@ -684,6 +678,21 @@ impl OpenCADStudio {
                     M::FlatShadedWithEdges => "Flat Shaded + Edges",
                     M::GouraudShadedWithEdges => "Gouraud Shaded + Edges",
                 };
+                // In a paper layout with an active (double-clicked)
+                // viewport, the picker drives that viewport entity's own
+                // render mode; the model-layout tab style is untouched.
+                if self.tabs[i].scene.set_active_viewport_render_mode(mode) {
+                    self.tabs[i].scene.bump_geometry();
+                    self.command_line
+                        .push_output(&format!("Viewport visual style: {label}"));
+                    return Task::none();
+                }
+                self.tabs[i].render_mode = mode;
+                // Keep the legacy `wireframe` bool synced — both wireframe
+                // modes set it, everything else clears it.
+                let wf = matches!(mode, M::Wireframe2D | M::Wireframe3D);
+                self.tabs[i].wireframe = wf;
+                self.ribbon.set_wireframe(wf);
                 self.tabs[i].visual_style = label.into();
                 // Re-upload face3d fills on the next frame — the render
                 // pipeline keys its upload cache off `geometry_epoch`.

src/app/view.rs

@@ -387,49 +387,7 @@ impl OpenCADStudio {
         // 3D face / mesh fills and edges are rendered for the active
         // tab. Hatch fills are deliberately *not* gated by this — the
         // document's FILLMODE still owns 2D fill state.
-        let render_modes: Vec<RenderModeChoice> = vec![
+        let info = render_mode_picker(tab.render_mode);
-            RenderModeChoice(acadrust::entities::ViewportRenderMode::Wireframe2D),
-            RenderModeChoice(acadrust::entities::ViewportRenderMode::Wireframe3D),
-            RenderModeChoice(acadrust::entities::ViewportRenderMode::HiddenLine),
-            RenderModeChoice(acadrust::entities::ViewportRenderMode::FlatShaded),
-            RenderModeChoice(acadrust::entities::ViewportRenderMode::GouraudShaded),
-            RenderModeChoice(acadrust::entities::ViewportRenderMode::FlatShadedWithEdges),
-            RenderModeChoice(acadrust::entities::ViewportRenderMode::GouraudShadedWithEdges),
-        ];
-        let info = container(
-            iced::widget::pick_list(
-                render_modes,
-                Some(RenderModeChoice(tab.render_mode)),
-                |c| Message::SetRenderMode(c.0),
-            )
-            .text_size(11),
-        )
-        .style(|_: &Theme| iced::widget::container::Style {
-            background: Some(iced::Background::Color(Color {
-                r: 0.10,
-                g: 0.10,
-                b: 0.10,
-                a: 0.75,
-            })),
-            border: iced::Border {
-                color: Color {
-                    r: 0.35,
-                    g: 0.35,
-                    b: 0.35,
-                    a: 1.0,
-                },
-                width: 1.0,
-                radius: 4.0.into(),
-            },
-            text_color: Some(Color {
-                r: 0.85,
-                g: 0.85,
-                b: 0.85,
-                a: 1.0,
-            }),
-            ..Default::default()
-        })
-        .padding([4, 8]);
 
         let viewport_mouse = mouse_area(container(
             iced::widget::Space::new().width(Fill).height(Fill),
@@ -931,7 +889,23 @@ fn paper_canvas_view<'a>(tab: &'a super::document::DocumentTab) -> Element<'a, M
             .width(Fill)
             .height(Fill);
 
-            return stack![paper_sheet, positioned, border_layer]
+            // Render-mode picker in the active viewport's top-left corner,
+            // mirroring the model-space overlay. Reads / writes the
+            // viewport entity's own render mode via SetRenderMode.
+            let vp_mode = scene
+                .active_viewport_render_mode()
+                .unwrap_or(acadrust::entities::ViewportRenderMode::Wireframe2D);
+            let picker_layer = column![
+                Space::new().height(iced::Length::Fixed(y + 4.0)),
+                row![
+                    Space::new().width(iced::Length::Fixed(x + 4.0)),
+                    iced::widget::opaque(render_mode_picker(vp_mode)),
+                ],
+            ]
+            .width(Fill)
+            .height(Fill);
+
+            return stack![paper_sheet, positioned, border_layer, picker_layer]
                 .width(Fill)
                 .height(Fill)
                 .into();
@@ -2017,6 +1991,60 @@ pub(super) fn recent_files_panel<'a>(recents: &'a [std::path::PathBuf]) -> Eleme
         .into()
 }
 
+// ── Render-mode picker ──────────────────────────────────────────────────────
+
+/// The 7-way visual-style `pick_list`, styled as a dark overlay chip.
+/// Shared by the model-space viewport (top-left) and each active
+/// paper-space viewport. Emits `SetRenderMode`, which the update loop
+/// routes to the active viewport entity or the model-layout tab.
+fn render_mode_picker<'a>(
+    current: acadrust::entities::ViewportRenderMode,
+) -> Element<'a, Message> {
+    use acadrust::entities::ViewportRenderMode as M;
+    let render_modes: Vec<RenderModeChoice> = vec![
+        RenderModeChoice(M::Wireframe2D),
+        RenderModeChoice(M::Wireframe3D),
+        RenderModeChoice(M::HiddenLine),
+        RenderModeChoice(M::FlatShaded),
+        RenderModeChoice(M::GouraudShaded),
+        RenderModeChoice(M::FlatShadedWithEdges),
+        RenderModeChoice(M::GouraudShadedWithEdges),
+    ];
+    container(
+        iced::widget::pick_list(render_modes, Some(RenderModeChoice(current)), |c| {
+            Message::SetRenderMode(c.0)
+        })
+        .text_size(11),
+    )
+    .style(|_: &Theme| iced::widget::container::Style {
+        background: Some(iced::Background::Color(Color {
+            r: 0.10,
+            g: 0.10,
+            b: 0.10,
+            a: 0.75,
+        })),
+        border: iced::Border {
+            color: Color {
+                r: 0.35,
+                g: 0.35,
+                b: 0.35,
+                a: 1.0,
+            },
+            width: 1.0,
+            radius: 4.0.into(),
+        },
+        text_color: Some(Color {
+            r: 0.85,
+            g: 0.85,
+            b: 0.85,
+            a: 1.0,
+        }),
+        ..Default::default()
+    })
+    .padding([4, 8])
+    .into()
+}
+
 // ── Dynamic-input field formatting ─────────────────────────────────────────
 
 /// Short prefix shown before a dynamic-input box's value.

src/scene/mod.rs

@@ -2199,6 +2199,36 @@ impl Scene {
         }
     }
 
+    /// Render mode of the active paper-space viewport, or `None` when no
+    /// viewport is active (PSPACE / model layout).
+    pub fn active_viewport_render_mode(
+        &self,
+    ) -> Option<acadrust::entities::ViewportRenderMode> {
+        let h = self.active_viewport?;
+        match self.document.get_entity(h) {
+            Some(acadrust::EntityType::Viewport(vp)) => Some(vp.render_mode),
+            _ => None,
+        }
+    }
+
+    /// Set the active paper-space viewport's render mode. Returns `true`
+    /// when a viewport was active and updated; `false` (no-op) otherwise,
+    /// so the caller can fall back to the model-layout render mode.
+    pub fn set_active_viewport_render_mode(
+        &mut self,
+        mode: acadrust::entities::ViewportRenderMode,
+    ) -> bool {
+        let Some(h) = self.active_viewport else {
+            return false;
+        };
+        if let Some(acadrust::EntityType::Viewport(vp)) = self.document.get_entity_mut(h) {
+            vp.render_mode = mode;
+            true
+        } else {
+            false
+        }
+    }
+
     /// View-rotation matrix for the active viewport (MSPACE), or the
     /// paper-space camera's matrix when not in MSPACE.
     /// Used by ViewCube hit-testing so clicks map to the correct camera.

src/scene/render.rs

@@ -512,6 +512,7 @@ impl Scene {
         vp_handle: Handle,
         hover_region: Option<usize>,
         bounds: Rectangle,
+        show_viewcube: bool,
     ) -> Primitive {
         let render_mode = match self.document.get_entity(vp_handle) {
             Some(EntityType::Viewport(vp)) => vp.render_mode,
@@ -551,7 +552,7 @@ impl Scene {
             cam_rotation: cam.view_rotation_mat(),
             hover_region,
             bg_color: self.bg_color,
-            show_viewcube: false,
+            show_viewcube,
             fill_mode: self.document.header.fill_mode,
             view_wireframe,
             mesh_fill: flags.mesh_fill,
@@ -570,8 +571,10 @@ impl Scene {
         hover_region: Option<usize>,
         bounds: Rectangle,
     ) -> PaperViewportPrimitive {
+        // The active (double-clicked) viewport shows the ViewCube gizmo,
+        // mirroring the model-space view.
         PaperViewportPrimitive(
-            self.build_viewport_primitive(vp_handle, hover_region, bounds),
+            self.build_viewport_primitive(vp_handle, hover_region, bounds, true),
         )
     }
 

src/scene/viewport_pane.rs

@@ -1,5 +1,6 @@
 use super::render::{CameraState, PaperViewportPrimitive, Primitive};
-use super::Scene;
+use super::{Scene, VIEWCUBE_PX};
+use crate::app::Message;
 use acadrust::Handle;
 use iced::widget::shader;
 use iced::{mouse, Event, Rectangle};
@@ -70,7 +71,7 @@ impl<'a> PaperViewportPane<'a> {
     }
 }
 
-impl<'a, Msg: std::fmt::Debug + Clone> shader::Program<Msg> for PaperViewportPane<'a> {
+impl<'a> shader::Program<Message> for PaperViewportPane<'a> {
     type State = CameraState;
     type Primitive = PaperViewportPrimitive;
 
@@ -90,9 +91,30 @@ impl<'a, Msg: std::fmt::Debug + Clone> shader::Program<Msg> for PaperViewportPan
         event: &Event,
         bounds: Rectangle,
         cursor: mouse::Cursor,
-    ) -> Option<iced::widget::Action<Msg>> {
+    ) -> Option<iced::widget::Action<Message>> {
         self.scene.update_viewcube_state(state, bounds, cursor);
-        let _ = event;
+        // A left click on the ViewCube snaps the viewport's view. The
+        // hit-test runs in bounds-relative coordinates so it matches the
+        // gizmo drawn in this viewport's top-right corner. Clicks outside
+        // the cube return None, so they fall through to the paper sheet
+        // for normal selection / drawing.
+        if let Event::Mouse(mouse::Event::ButtonPressed(mouse::Button::Left)) = event {
+            if let Some(pos) = cursor.position_in(bounds) {
+                let rot = self.scene.active_view_rotation_mat();
+                if let Some(region) = super::hit_test(
+                    pos.x,
+                    pos.y,
+                    bounds.width,
+                    bounds.height,
+                    rot,
+                    VIEWCUBE_PX,
+                ) {
+                    return Some(iced::widget::Action::publish(Message::ViewCubeSnap(
+                        region,
+                    )));
+                }
+            }
+        }
         None
     }
 
@@ -127,7 +149,7 @@ impl<'a, Msg: std::fmt::Debug + Clone> shader::Program<Msg> for ViewportPane<'a>
             ),
             ViewportPaneMode::Paper { handle } => {
                 self.scene
-                    .build_viewport_primitive(*handle, state.hover_region, bounds)
+                    .build_viewport_primitive(*handle, state.hover_region, bounds, false)
             }
         }
     }