fix: restore preview edge default target position on cell hover by LOUISNOYEZ · Pull Request #1025 · maxGraph/maxGraph

LOUISNOYEZ · 2026-03-24T11:21:40Z

PR Checklist

Addresses an existing open issue: closes #<the_issue_number_here>. If not, explain why (minor changes, etc.).
You have discussed this issue with the maintainers of maxGraph, and you are assigned to the issue.
The scope of the PR is sufficiently narrow to be examined in a single session. A PR covering several issues must be split into separate PRs. Do not create a large PR, otherwise it cannot be reviewed and you will be asked to split it later or the PR will be closed.
I have added tests to prove my fix is effective or my feature works. This can be done in the form of automatic tests in packages/core/_tests_ or a new or altered Storybook story in packages/html/stories (an existing story may also demonstrate the change).
I have provided screenshot/videos to demonstrate the change. If no releavant, explain why.
I have added or edited necessary documentation, or no docs changes are needed.
The PR title follows the "Conventional Commits" guidelines.

Overview

Restore connection handler mxgraph behavior.
Delete preview edge entryX and entryY style properties when hovering a cell without without hovering a specific target connection point instead of setting them to 0. Currently, the connection preview entry position snaps to the top left corner of cell shapes, which is not intended behavior.

Bug description

This pull request is intended to fix issue Orthogonal Story: the edge connection preview not always match the final edge points #841 and other issues involving misposition of the connection preview when using the connection handler.

Demonstration using the Anchor story

Current maxgraph behavior : The connection preview snaps to the top left of the cell shape.

connection_preview_wrong.mp4

Intended mxgraph behavior : The connection preview snaps to the bottom center of the cell shape.

connection_preview_right.mp4

Analysis

The behavior change was introduced in commit 648e324 where the connection handler file was changed from

maxGraph/packages/core/src/view/connection/ConnectionHandler.ts

Lines 1497 to 1503 in 0453da2

    
           if (constraint != null && constraint.point != null) { 
        
             this.edgeState.style.entryX = constraint.point.x; 
        
             this.edgeState.style.entryY = constraint.point.y; 
        
           } else { 
        
             delete this.edgeState.style.entryX; 
        
             delete this.edgeState.style.entryY; 
        
           }

to

maxGraph/packages/core/src/view/connection/ConnectionHandler.ts

Lines 1491 to 1497 in 648e324

    
           if (constraint && constraint.point) { 
        
             this.edgeState.style.entryX = constraint.point.x; 
        
             this.edgeState.style.entryY = constraint.point.y; 
        
           } else { 
        
             this.edgeState.style.entryX = 0; 
        
             this.edgeState.style.entryY = 0; 
        
           }

Which remains to this day. Fixing the issue consists in reverting to the original code.

Notes

Although this pull request reverts to the initial mxgraph behavior, it provides no motivation for the initial behavior in the first place.
I've added no tests under packages/core/__tests__ as the issue is related to a transient rendering artefact. Correctness can be assed using any story involving the connection handler where its updateEdgeState method has not been overriden.

Keywords

closes #841

Summary by CodeRabbit

Bug Fixes
- Improved edge preview rendering by removing stale connection coordinate styling when preview constraints are absent, producing more accurate connection visuals.
Documentation
- Expanded and clarified connection-point docs: normalized entryX/entryY/exitX/exitY semantics (typical 0–1 range), how perimeter falls back to center, and how pixel offsets (entryDx/entryDy/exitDx/exitDy) apply after point computation.

delete preview edge entryX and entryY style properties when hovering a cell without without hovering a specific target connection point.

coderabbitai · 2026-03-24T11:22:17Z

Walkthrough

When no connection constraint.point exists, ConnectionHandler.updateEdgeState now deletes edgeState.style.entryX and edgeState.style.entryY instead of setting them to 0. JSDoc for CellStateStyle connection-point properties was expanded and clarified.

Changes

Cohort / File(s)	Summary
Edge Style Property Handling `packages/core/src/view/plugin/ConnectionHandler.ts`	In `updateEdgeState`, remove `edgeState.style.entryX` and `edgeState.style.entryY` via `delete` when no `constraint.point` is present, replacing prior assignments of `0`.
Type / JSDoc Clarifications `packages/core/src/types.ts`	Expanded and corrected JSDoc for `CellStateStyle` connection properties (`entryX/entryY`, `exitX/exitY`, `entryDx/entryDy`, `exitDx/exitDy`, `entryPerimeter`, `exitPerimeter`, `perimeter`), clarifying normalized coordinate semantics, offsets, and fallback behaviors.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Possibly related PRs

feat: accept more nullish parameter in various methods #892 — Modifies ConnectionHandler.updateEdgeState and related handling of entryX/entryY, addressing similar edge preview/entry coordinate behavior.

Suggested labels

enhancement

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description check	✅ Passed	The PR description is comprehensive and complete: includes a filled checklist, clear bug description with videos, analysis of the problematic change, and references issue `#841`. All essential information is provided.
Linked Issues check	✅ Passed	The code changes directly address issue `#841` by removing entryX/entryY property deletion and setting them to 0, restoring mxGraph behavior where the preview matches final edge points.
Out of Scope Changes check	✅ Passed	All changes are in-scope: documentation updates clarify connection-point styling properties in types.ts, and ConnectionHandler.ts changes fix the preview behavior issue described in `#841`.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Title check	✅ Passed	The title clearly and concisely describes the main fix: restoring the preview edge's default target position behavior on cell hover, which directly aligns with the changeset's primary objective.

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tbouffard · 2026-03-25T14:00:21Z

ℹ️ I have been looking at the entryX/entryY properties. entryX is "The connection point in relative horizontal coordinates of an edge with its target terminal."
Setting entryX=0 and entryY=0, means that the constraint point is set to the point on the top left of the shape, which is what we previously saw.
When not setting entryX and entryY, no constraint point is used, and this is what we want to use here. See

maxGraph/packages/core/src/view/mixin/ConnectionsMixin.ts

Lines 160 to 168 in 24357a7

    
           const x = edge.style[source ? 'exitX' : 'entryX']; 
        
           if (x !== undefined) { 
        
             const y = edge.style[source ? 'exitY' : 'entryY']; 
        
             if (y !== undefined) { 
        
               point = new Point(x, y); 
        
             } 
        
           }

sonarqubecloud · 2026-03-26T13:34:56Z

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

redfish4ktc

LGTM, thanks for this contribution and sorry for having taken so long to review it 😸

fix: restore connection handler mxGraph behavior

a8dbc41

delete preview edge entryX and entryY style properties when hovering a cell without without hovering a specific target connection point.

LOUISNOYEZ marked this pull request as ready for review March 24, 2026 11:22

redfish4ktc added 2 commits March 25, 2026 15:43

CellStateStyle: improve JSDoc (entryX, entryY)

c37947a

CellStateStyle: improve JSDoc for entry and exit properties

8de4221

tbouffard changed the title ~~fix(connection): restore connection handler mxGraph behavior~~ fix: restore preview edge default target position on cell hover Apr 28, 2026

redfish4ktc approved these changes Apr 28, 2026

View reviewed changes

redfish4ktc merged commit fc7aa28 into maxGraph:main Apr 28, 2026
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fix: restore preview edge default target position on cell hover#1025

fix: restore preview edge default target position on cell hover#1025
redfish4ktc merged 3 commits into
maxGraph:mainfrom
LOUISNOYEZ:fix/connection_handler_preview_restore_default_position

LOUISNOYEZ commented Mar 24, 2026 •

edited by coderabbitai Bot

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	if (constraint != null && constraint.point != null) {
	this.edgeState.style.entryX = constraint.point.x;
	this.edgeState.style.entryY = constraint.point.y;
	} else {
	delete this.edgeState.style.entryX;
	delete this.edgeState.style.entryY;
	}

	if (constraint && constraint.point) {
	this.edgeState.style.entryX = constraint.point.x;
	this.edgeState.style.entryY = constraint.point.y;
	} else {
	this.edgeState.style.entryX = 0;
	this.edgeState.style.entryY = 0;
	}

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LOUISNOYEZ commented Mar 24, 2026 • edited by coderabbitai Bot Loading Uh oh! There was an error while loading. Please reload this page.

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PR Checklist

Overview

Bug description

Analysis

Notes

Keywords

Summary by CodeRabbit

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Walkthrough

Changes

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Possibly related PRs

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tbouffard commented Mar 25, 2026

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sonarqubecloud Bot commented Mar 26, 2026

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LOUISNOYEZ commented Mar 24, 2026 •

edited by coderabbitai Bot

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coderabbitai Bot commented Mar 24, 2026 •

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