Extending from point allows a handle to be colinear with 2 others

Reproduction

New document
Use pen tool
Draw path containing an anchor with colinear handles (not an end point and not broken)
Extend from the anchor with colinear handles by clicking (do not drag)
Finish the path
Use path tool
Drag the handle noting how the handle tries to be colinear with two different handles causing strange behaviour.

Video

colinear_twice.mp4

Resolution

When extending from an existing point that is already connected to two segments, do not make it colinear with the existing path. If the user does not drag to place the handle then it should probably be placed on top of the anchor. When there is only one segment connected to a point, it may be desirable (?) to keep the current behaviour.

Relevant code

Graphite/editor/src/messages/tool/tool_messages/pen_tool.rs

Lines 1397 to 1401 in ae321b3

    
           	/// Perform extension of an existing path 
        
           	fn extend_existing_path(&mut self, document: &DocumentMessageHandler, layer: LayerNodeIdentifier, point: PointId, position: DVec2) { 
        
           		let vector = document.network_interface.compute_modified_vector(layer); 
        
           		let (handle_start, in_segment) = if let Some(vector) = &vector { 
        
           			vector

Graphite/editor/src/messages/tool/tool_messages/pen_tool.rs

Lines 834 to 842 in ae321b3

    
           if let Some(h1) = handles[0].to_manipulator_point().get_position(&vector) { 
        
           	let angle = (h1 - last_point.pos).angle_to(last_point.handle_start - last_point.pos); 
        
           	let pi = std::f64::consts::PI; 
        
           	let colinear = (angle - pi).abs() < 1e-6 || (angle + pi).abs() < 1e-6; 
        
           	responses.add(GraphOperationMessage::Vector { 
        
           		layer, 
        
           		modification_type: VectorModificationType::SetG1Continuous { handles, enabled: colinear }, 
        
           	}); 
        
           }

@0HyperCube

@0HyperCube I want to solve this issue.

@parthdude07

Hi @parthdude07. You are welcome to attempt any issue you wish. Please see the contributor guide for more information. Note issues are not assigned to new contributors until they open a draft PR to avoid ghost assignments.

Fix GraphiteEditor#4618: Prevent colinear handles when extending from…

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Extending from point allows a handle to be colinear with 2 others #4618

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	/// Perform extension of an existing path
	fn extend_existing_path(&mut self, document: &DocumentMessageHandler, layer: LayerNodeIdentifier, point: PointId, position: DVec2) {
	let vector = document.network_interface.compute_modified_vector(layer);
	let (handle_start, in_segment) = if let Some(vector) = &vector {
	vector

	if let Some(h1) = handles[0].to_manipulator_point().get_position(&vector) {
	let angle = (h1 - last_point.pos).angle_to(last_point.handle_start - last_point.pos);
	let pi = std::f64::consts::PI;
	let colinear = (angle - pi).abs() < 1e-6 \|\| (angle + pi).abs() < 1e-6;
	responses.add(GraphOperationMessage::Vector {
	layer,
	modification_type: VectorModificationType::SetG1Continuous { handles, enabled: colinear },
	});
	}

Extending from point allows a handle to be colinear with 2 others #4618

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parthdude07 commented on Sep 29, 2026

0HyperCube commented on Sep 29, 2026

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