navigation: selectable mouse navigation style

Options → User Preferences → Navigation style picks which mouse
gestures pan and orbit the model view (#1480):

- CAD (default): middle button pans, Shift + middle button orbits.
- Blender: middle button orbits, Shift + middle button pans.
- CATIA: middle button pans; pressing the left button during it orbits,
  so 3D navigation needs only the mouse.

An armed orbit tool always orbits. The choice is saved with the user
settings.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/app/mod.rs

@@ -650,6 +650,11 @@ pub(super) struct OpenCADStudio {
     polar_increment_deg: f32,
     /// Reverse the mouse-wheel zoom direction when true (ZOOMWHEEL = 1).
     zoom_wheel_reversed: bool,
+    /// Which mouse gestures pan and orbit the model view.
+    navigation_style: crate::app::settings::NavigationStyle,
+    /// CATIA navigation: the left button went down while the middle one was
+    /// held, so the middle drag orbits until it is released.
+    nav_left_with_middle: bool,
     /// Scroll pans and Ctrl+scroll zooms (touchpads); see `scroll_intent`.
     touchpad_pan: bool,
     /// Multi-finger gestures on a touch screen.
@@ -2657,6 +2662,7 @@ pub enum Message {
     CommandLineOpacityChanged(u8),
     /// Toggle reversing the mouse-wheel zoom direction (ZOOMWHEEL).
     ZoomWheelReversedChanged(bool),
+    NavigationStyleChanged(crate::app::settings::NavigationStyle),
     TouchpadPanChanged(bool),
     /// Options: show the pull-down menus (MENUBAR).
     MenuBarChanged(bool),
@@ -4632,6 +4638,8 @@ impl OpenCADStudio {
             polar_mode: false,
             polar_increment_deg: 45.0,
             zoom_wheel_reversed: false,
+            navigation_style: Default::default(),
+            nav_left_with_middle: false,
             touchpad_pan: false,
             touch: Default::default(),
             touch_offset: None,

src/app/settings.rs

@@ -204,6 +204,33 @@ pub fn zoom_notch_percent(factor: i32) -> f32 {
     (1.0 - ratio) * 100.0
 }
 
+/// Which mouse gestures pan and orbit the model view.
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum NavigationStyle {
+    /// Middle button pans; Shift + middle button orbits.
+    #[default]
+    Cad,
+    /// Middle button orbits; Shift + middle button pans.
+    Blender,
+    /// Middle button pans; middle and left buttons together orbit.
+    Catia,
+}
+
+impl NavigationStyle {
+    pub const ALL: [NavigationStyle; 3] = [Self::Cad, Self::Blender, Self::Catia];
+}
+
+impl std::fmt::Display for NavigationStyle {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str(&match self {
+            Self::Cad => crate::t!("CAD: Shift + middle button orbits"),
+            Self::Blender => crate::t!("Blender: middle button orbits, Shift pans"),
+            Self::Catia => crate::t!("CATIA: middle + left button orbits"),
+        })
+    }
+}
+
 /// Active pair of axes while isometric drafting is enabled.
 #[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Serialize, Deserialize)]
 pub enum IsoPlane {
@@ -388,6 +415,7 @@ pub struct UserSettings {
     pub polar: bool,
     pub polar_increment_deg: f32,
     pub zoom_wheel_reversed: bool,
+    pub navigation_style: NavigationStyle,
     /// Scrolling pans and Ctrl+scroll (a touchpad pinch) zooms, for a
     /// touchpad that reports two-finger drags as wheel scrolls.
     pub touchpad_pan: bool,
@@ -891,6 +919,7 @@ impl Default for UserSettings {
             polar: false,
             polar_increment_deg: 45.0,
             zoom_wheel_reversed: false,
+            navigation_style: NavigationStyle::Cad,
             touchpad_pan: false,
             ui_scale_percent: 100,
             zoom_factor: 60,

src/app/update/file.rs

@@ -778,6 +778,7 @@ impl OpenCADStudio {
             polar: self.polar_mode,
             polar_increment_deg: self.polar_increment_deg,
             zoom_wheel_reversed: self.zoom_wheel_reversed,
+            navigation_style: self.navigation_style,
             touchpad_pan: self.touchpad_pan,
             ui_scale_percent: self.ui_scale_percent,
             zoom_factor: self.zoom_factor,
@@ -913,6 +914,7 @@ impl OpenCADStudio {
         self.polar_mode = s.polar;
         self.polar_increment_deg = s.polar_increment_deg;
         self.zoom_wheel_reversed = s.zoom_wheel_reversed;
+        self.navigation_style = s.navigation_style;
         self.touchpad_pan = s.touchpad_pan;
         self.ui_scale_percent = crate::app::settings::clamp_ui_scale(s.ui_scale_percent);
         self.zoom_factor = crate::app::settings::clamp_zoom_factor(s.zoom_factor);

src/app/update/mod.rs

@@ -4482,6 +4482,25 @@ impl OpenCADStudio {
                 Task::none()
             }
 
+            // CATIA navigation: the left button pressed during a middle drag
+            // turns the drag into an orbit instead of starting a pick.
+            Message::ViewportLeftPressAt(_) | Message::ViewportLeftPress | Message::PanePress(_)
+                if self.navigation_style == crate::app::settings::NavigationStyle::Catia
+                    && self.tabs[self.active_tab]
+                        .scene
+                        .selection
+                        .borrow()
+                        .input
+                        .middle_down =>
+            {
+                self.nav_left_with_middle = true;
+                Task::none()
+            }
+            Message::ViewportLeftRelease | Message::PaneRelease(_) if self.nav_left_with_middle => {
+                self.nav_left_with_middle = false;
+                Task::none()
+            }
+
             Message::ViewportMove(p) => self.on_viewport_move(p),
 
             Message::ViewportExit => self.on_viewport_exit(),
@@ -4686,6 +4705,7 @@ impl OpenCADStudio {
             }
 
             Message::ViewportMiddleRelease => {
+                self.nav_left_with_middle = false;
                 let i = self.active_tab;
                 let mut sel = self.tabs[i].scene.selection.borrow_mut();
                 sel.input.middle_down = false;
@@ -9225,6 +9245,12 @@ impl OpenCADStudio {
                 Task::none()
             }
 
+            Message::NavigationStyleChanged(style) => {
+                self.navigation_style = style;
+                self.persist_settings_if_changed();
+                Task::none()
+            }
+
             Message::MenuBarChanged(shown) => {
                 self.show_menu_bar = shown;
                 self.persist_settings_if_changed();

src/app/update/viewport.rs

@@ -1416,7 +1416,7 @@ impl OpenCADStudio {
                 // — the requested Zoom=wheel / Pan=MMB / Rotate=Shift+MMB
                 // scheme (#229). Floating viewports and paper keep the
                 // plain MMB pan.
-                if self.shift_down || self.tabs[i].orbit_mode {
+                if self.middle_drag_orbits(i) {
                     if self.tabs[i].scene.active_viewport.is_some() {
                         // Orbit the floating viewport's own model view.
                         drop(sel);
@@ -3165,6 +3165,18 @@ impl OpenCADStudio {
         Task::none()
     }
 
+    /// Whether a middle-button drag orbits rather than pans, by the
+    /// navigation style (an armed orbit tool always orbits).
+    fn middle_drag_orbits(&self, i: usize) -> bool {
+        use crate::app::settings::NavigationStyle;
+        self.tabs[i].orbit_mode
+            || match self.navigation_style {
+                NavigationStyle::Cad => self.shift_down,
+                NavigationStyle::Blender => !self.shift_down,
+                NavigationStyle::Catia => self.nav_left_with_middle,
+            }
+    }
+
     pub(crate) fn on_viewport_exit(&mut self) -> Task<Message> {
         let i = self.active_tab;
         self.tabs[i].measurement.live_visible = false;

src/app/view/modal.rs

@@ -312,6 +312,7 @@ impl OpenCADStudio {
                             show_ribbon: !self.ribbon_closed,
                             hatch_associative: self.hatch_associative,
                             zoom_wheel_reversed: self.zoom_wheel_reversed,
+                            navigation_style: self.navigation_style,
                             touchpad_pan: self.touchpad_pan,
                             ui_scale_percent: self.ui_scale_percent,
                             zoom_factor: self.zoom_factor,

src/locale_catalog.rs

@@ -5070,6 +5070,10 @@ pub(super) fn message_attribute(source: &str) -> Option<(&'static str, &'static
         "User Preferences" => Some(("common", "user-preferences")),
         "Zoom" => Some(("common", "zoom")),
         "Reverse mouse wheel zoom (ZOOMWHEEL)" => Some(("common", "reverse-mouse-wheel-zoom-zoomwheel")),
+        "Navigation style" => Some(("common", "navigation-style")),
+        "CAD: Shift + middle button orbits" => Some(("common", "nav-style-cad")),
+        "Blender: middle button orbits, Shift pans" => Some(("common", "nav-style-blender")),
+        "CATIA: middle + left button orbits" => Some(("common", "nav-style-catia")),
         "Touchpad: scroll pans, Ctrl+scroll or pinch zooms" => Some(("common", "touchpad-scroll-pans-ctrl-scroll-or-pinch-zooms")),
         "Interface scale" => Some(("common", "interface-scale")),
         "Zoom factor" => Some(("common", "zoom-factor")),

src/ui/window/options.rs

@@ -63,6 +63,8 @@ pub struct AppPrefs {
     pub hatch_associative: bool,
     /// ZOOMWHEEL: reverse the mouse-wheel zoom direction.
     pub zoom_wheel_reversed: bool,
+    /// Which mouse gestures pan and orbit the model view.
+    pub navigation_style: crate::app::settings::NavigationStyle,
     /// Scroll pans and Ctrl+scroll zooms (touchpads).
     pub touchpad_pan: bool,
     /// Interface scale in percent.
@@ -1274,6 +1276,16 @@ pub fn view_window<'a>(
         Space::new().height(10),
         spacemouse,
         Space::new().height(12),
+        text(crate::t!("Navigation style")).size(15),
+        Space::new().height(10),
+        iced::widget::pick_list(
+            Some(prefs.navigation_style),
+            crate::app::settings::NavigationStyle::ALL,
+            |style| style.to_string(),
+        )
+        .on_select(Message::NavigationStyleChanged)
+        .text_size(12),
+        Space::new().height(12),
         text(crate::t!("Zoom")).size(15),
         Space::new().height(10),
         row![