feat(snap): expose MTP in snap override and context menus

The MTP/M2P midpoint-between-two-points modifier existed as a typed transparent command only. Add it to the Shift+RMB snap override menu as an icon-only cell after Parallel (hover tooltip, no text) with a new osnap/mtp.svg marker, plus a context-menu entry while a point prompt is active.

assets/icons/osnap/mtp.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="none" stroke="#B4B6B9" stroke-width="1.5" stroke-linecap="round" stroke-linejoin="round"><path d="M12 8.26 16.05 15.74H7.95Z"/><circle cx="4.5" cy="19.5" r="1.5" fill="#B4B6B9" stroke="none"/><circle cx="19.5" cy="4.5" r="1.5" fill="#B4B6B9" stroke="none"/></svg>

src/app/mod.rs

@@ -1892,9 +1892,12 @@ pub enum Message {
     WebFieldCopy,
     /// Web only: the focused field's text — write it to the clipboard.
     WebFieldCopyText(Option<String>),
-    /// Pick from the one-shot snap override menu (Shift+RMB): only this snap
-    /// applies to the next point pick, then the configuration restores (#337).
+    /// Pick from the one-shot snap override menu (Shift+RMB): only this
+    /// snap applies to the next point pick, then the configuration restores (#337).
     SnapOverridePick(crate::snap::SnapType),
+    /// Mid Between 2 Points from the snap menu: modal 2-pick modifier over
+    /// the active point prompt (AutoCAD `_M2P`).
+    SnapOverrideMtp,
     /// Close the one-shot snap override menu without picking.
     SnapOverrideClose,
     /// Open a path from the Start tab's recent-documents list (skips the

src/app/update/mod.rs

@@ -680,6 +680,29 @@ impl OpenCADStudio {
                 Task::none()
             }
 
+            Message::SnapOverrideMtp => {
+                self.snap_override_popup = None;
+                self.tabs[self.active_tab]
+                    .scene
+                    .selection
+                    .borrow_mut()
+                    .context_menu = None;
+                // Same guard as typed MTP/M2P: point step, not entity pick.
+                let i = self.active_tab;
+                let allowed = self.tabs[i].active_cmd.as_ref().is_some_and(|c| {
+                    (!c.input_kind().wants_text() || c.point_step_accepts_keywords())
+                        && !c.needs_entity_pick()
+                });
+                if allowed {
+                    self.start_mtp_modifier(i);
+                } else {
+                    self.command_line.push_info(
+                        crate::t!("MTP needs an active point prompt.").as_ref(),
+                    );
+                }
+                Task::none()
+            }
+
             Message::SnapOverrideClose => {
                 self.snap_override_popup = None;
                 Task::none()

src/app/view/mod.rs

@@ -1629,6 +1629,11 @@ bg={bg_ms:.1}ms n={view_count}"
             };
             if let Some(p) = ctx_pos {
                 let has_cmd = tab.active_cmd.is_some();
+                // Same guard as typed MTP/M2P and SnapOverrideMtp.
+                let has_point_step = tab.active_cmd.as_ref().is_some_and(|c| {
+                    (!c.input_kind().wants_text() || c.point_step_accepts_keywords())
+                        && !c.needs_entity_pick()
+                });
                 let has_selection = !tab.scene.selected.is_empty();
                 let isolation_active = tab.scene.is_isolation_active();
                 let last_cmds: Vec<String> = self
@@ -1647,6 +1652,7 @@ bg={bg_ms:.1}ms n={view_count}"
                     isolation_active,
                     last_cmds,
                     draworder_open,
+                    has_point_step,
                 ));
             }
         }

src/app/view/overlay.rs

@@ -1102,6 +1102,7 @@ pub(super) fn viewport_context_menu_overlay(
     isolation_active: bool,
     last_cmds: Vec<String>,
     draworder_open: bool,
+    has_point_step: bool,
 ) -> Element<'static, Message> {
     let item = |label: String, msg: Message| -> Element<'static, Message> {
         button(text(label).size(12))
@@ -1146,6 +1147,15 @@ pub(super) fn viewport_context_menu_overlay(
     if has_cmd {
         items.push(item(t!("Cancel").into_owned(), Message::CommandEscape));
         items.push(item(t!("Enter").into_owned(), Message::CommandFinalize));
+        // MTP (`_M2P`) goes last, after Parallel: two picks, so not a
+        // `SnapType`, but same icon-only cell with hover tooltip.
+        if has_point_step {
+            items.push(sep());
+            items.push(item(
+                t!("Mid Between 2 Points (M2P)").into_owned(),
+                Message::SnapOverrideMtp,
+            ));
+        }
     } else {
         if !last_cmds.is_empty() {
             let last = last_cmds[0].clone();
@@ -1262,21 +1272,19 @@ pub(super) fn viewport_context_menu_overlay(
 
 /// One-shot snap override menu (Shift+RMB, #337): a cursor-anchored grid of
 /// snap ICONS only — the names show as hover tooltips. Picking one applies
-/// that snap to just the next point pick.
+/// that snap to just the next point pick; the trailing MTP cell instead
+/// suspends the prompt for two picks and returns their midpoint.
 pub(super) fn snap_override_overlay(pos: iced::Point) -> Element<'static, Message> {
     const COLS: usize = 4;
 
-    let cell = |snap_type: crate::snap::SnapType, label: &'static str| -> Element<'static, Message> {
-        let icon = container(crate::ui::icons::themed::<Message>(
-            crate::ui::icons::osnap(snap_type),
-            16.0,
-        ))
+    let cell_icon = |icon: &'static [u8], label: String, msg: Message| -> Element<'static, Message> {
+        let icon = container(crate::ui::icons::themed::<Message>(icon, 16.0))
         .width(26)
         .height(26)
         .align_x(iced::Center)
         .align_y(iced::Center);
         let btn = button(icon)
-            .on_press(Message::SnapOverridePick(snap_type))
+            .on_press(msg)
             .style(|theme: &Theme, status| button::Style {
                 background: matches!(
                     status,
@@ -1312,11 +1320,29 @@ pub(super) fn snap_override_overlay(pos: iced::Point) -> Element<'static, Messag
         .into()
     };
 
+    // MTP (`_M2P`) goes last, after Parallel: two picks, so not a
+    // `SnapType`, but same icon-only cell with hover tooltip.
+    let mut cells: Vec<Element<'static, Message>> = Vec::with_capacity(
+        crate::snap::ALL_SNAP_MODES.len() + 1,
+    );
+    for &(snap_type, _glyph, label) in crate::snap::ALL_SNAP_MODES {
+        cells.push(cell_icon(
+            crate::ui::icons::osnap(snap_type),
+            label.to_string(),
+            Message::SnapOverridePick(snap_type),
+        ));
+    }
+    cells.push(cell_icon(
+        crate::ui::icons::mtp_icon(),
+        t!("Mid Between 2 Points (M2P)").into_owned(),
+        Message::SnapOverrideMtp,
+    ));
     let mut grid = column![].spacing(2);
-    for chunk in crate::snap::ALL_SNAP_MODES.chunks(COLS) {
+    while !cells.is_empty() {
+        let n = cells.len().min(COLS);
         let mut r = row![].spacing(2);
-        for &(snap_type, _glyph, label) in chunk {
-            r = r.push(cell(snap_type, label));
+        for c in cells.drain(..n) {
+            r = r.push(c);
         }
         grid = grid.push(r);
     }

src/ui/icons.rs

@@ -43,6 +43,7 @@ static OSNAP_NEAREST: &[u8] = include_bytes!("../../assets/icons/osnap/nearest.s
 static OSNAP_APPARENT: &[u8] = include_bytes!("../../assets/icons/osnap/apparent.svg");
 static OSNAP_PARALLEL: &[u8] = include_bytes!("../../assets/icons/osnap/parallel.svg");
 static OSNAP_GRID: &[u8] = include_bytes!("../../assets/icons/osnap/grid.svg");
+static OSNAP_MTP: &[u8] = include_bytes!("../../assets/icons/osnap/mtp.svg");
 
 static LAY_ON: &[u8] = include_bytes!("../../assets/icons/layers/layon.svg");
 static LAY_OFF: &[u8] = include_bytes!("../../assets/icons/layers/layoff.svg");
@@ -595,6 +596,11 @@ pub fn osnap(snap: crate::snap::SnapType) -> &'static [u8] {
     }
 }
 
+/// MTP menu icon: modal 2-pick modifier, not a persistent `SnapType` mode.
+pub fn mtp_icon() -> &'static [u8] {
+    OSNAP_MTP
+}
+
 /// Layer visibility icon bytes (on / off).
 pub fn layer_visible(visible: bool) -> &'static [u8] {
     if visible {