Disable the Path tool's "Colinear Handles" checkbox when no interior anchors are selected (#2339)

* disable "Colinear Handles" checkbox when only endpoint or its handle is selected

* small refactor

* ignore endpoints when calculating multiple selected points colinearity

---------

Co-authored-by: indierusty <priyaayadav@gmail.com>
Co-authored-by: Keavon Chambers <keavon@keavon.com>

editor/src/messages/tool/common_functionality/shape_editor.rs

@@ -575,7 +575,7 @@ impl ShapeState {
 		Some(())
 	}
 
-	/// Iterates over the selected manipulator groups, returning whether their handles have mixed, colinear, or free angles.
+	/// Iterates over the selected manipulator groups exluding endpoints, returning whether their handles have mixed, colinear, or free angles.
 	/// If there are no points selected this function returns mixed.
 	pub fn selected_manipulator_angles(&self, network_interface: &NodeNetworkInterface) -> ManipulatorAngle {
 		// This iterator contains a bool indicating whether or not selected points' manipulator groups have colinear handles.
@@ -583,7 +583,13 @@ impl ShapeState {
 			.selected_shape_state
 			.iter()
 			.map(|(&layer, selection_state)| (network_interface.compute_modified_vector(layer), selection_state))
-			.flat_map(|(data, selection_state)| selection_state.selected_points.iter().map(move |&point| data.as_ref().is_some_and(|data| data.colinear(point))));
+			.flat_map(|(data, selection_state)| {
+				selection_state.selected_points.iter().filter_map(move |&point| {
+					let Some(data) = &data else { return None };
+					let Some(_) = point.get_handle_pair(&data) else { return None }; // ignores the endpoints.
+					Some(data.colinear(point))
+				})
+			});
 
 		let Some(first_is_colinear) = points_colinear_status.next() else { return ManipulatorAngle::Mixed };
 		if points_colinear_status.any(|point| first_is_colinear != point) {

editor/src/messages/tool/tool_messages/path_tool.rs

@@ -175,7 +175,7 @@ impl LayoutHolder for PathTool {
 		// TODO: Remove `unwrap_or_default` once checkboxes are capable of displaying a mixed state
 		.unwrap_or_default();
 		let colinear_handle_checkbox = CheckboxInput::new(colinear_handles_state)
-			.disabled(self.tool_data.selection_status.is_none())
+			.disabled(!self.tool_data.can_toggle_colinearity)
 			.on_update(|&CheckboxInput { checked, .. }| {
 				if checked {
 					PathToolMessage::ManipulatorMakeHandlesColinear.into()
@@ -186,7 +186,7 @@ impl LayoutHolder for PathTool {
 			.tooltip(colinear_handles_tooltip)
 			.widget_holder();
 		let colinear_handles_label = TextLabel::new("Colinear Handles")
-			.disabled(self.tool_data.selection_status.is_none())
+			.disabled(!self.tool_data.can_toggle_colinearity)
 			.tooltip(colinear_handles_tooltip)
 			.widget_holder();
 
@@ -359,7 +359,10 @@ struct PathToolData {
 	opposing_handle_lengths: Option<OpposingHandleLengths>,
 	/// Describes information about the selected point(s), if any, across one or multiple shapes and manipulator point types (anchor or handle).
 	/// The available information varies depending on whether `None`, `One`, or `Multiple` points are currently selected.
+	/// NOTE: It must be updated using `update_selection_status` to ensure `can_toggle_colinearity` stays synchronized with the current selection.
 	selection_status: SelectionStatus,
+	/// `true` if we can change the current selection to colinear or not.
+	can_toggle_colinearity: bool,
 	segment: Option<ClosestSegment>,
 	snap_cache: SnapCache,
 	double_click_handled: bool,
@@ -415,6 +418,20 @@ impl PathToolData {
 		}
 	}
 
+	fn update_selection_status(&mut self, shape_editor: &mut ShapeState, document: &DocumentMessageHandler) {
+		let selection_status = get_selection_status(&document.network_interface, shape_editor);
+
+		self.can_toggle_colinearity = match &selection_status {
+			SelectionStatus::None => false,
+			SelectionStatus::One(single_selected_point) => {
+				let vector_data = document.network_interface.compute_modified_vector(single_selected_point.layer).unwrap();
+				single_selected_point.id.get_handle_pair(&vector_data).is_some()
+			}
+			SelectionStatus::Multiple(_) => true,
+		};
+		self.selection_status = selection_status;
+	}
+
 	fn start_insertion(&mut self, responses: &mut VecDeque<Message>, segment: ClosestSegment) -> PathToolFsmState {
 		if self.segment.is_some() {
 			warn!("Segment was `Some(..)` before `start_insertion`")
@@ -1302,7 +1319,7 @@ impl Fsm for PathToolFsmState {
 					point_select_state: shape_editor.get_dragging_state(&document.network_interface),
 					colinear,
 				};
-				tool_data.selection_status = get_selection_status(&document.network_interface, shape_editor);
+				tool_data.update_selection_status(shape_editor, document);
 				self
 			}
 			(_, PathToolMessage::ManipulatorMakeHandlesColinear) => {