ADDITIONAL SYSTEM INFORMATION :
This issue was reproduced on Windows10 but also in Linux environments.
Tested locally: the bug does NOT appear in jdk20+24 but appears as of jdk20+25 and upper versions JDK21 and on as well.

A DESCRIPTION OF THE PROBLEM :
Random lines - segments and straight lines - , that seem to be tangents of original expected lines, appear when painting basic strokes.
It can lead to some complex graphics not being readable anymore and mislead users in the interpretation of the images.

I identified this commit as the potential root cause for this bug: https://github.com/openjdk/jdk/commit/5b3d86f2296ec011f70cebe80a221b8a6f926912

REGRESSION : Last worked in version 19

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :

With jdk20+25 compile it and run net.sf.jcgm.examples.Viewer.
In the GUI of the app, paste the directory containing the CGM file in the "Test Folder" and press enter.
Zoom and zoom out, play around with the size the panel: unexpected straight lines and segments will appear and disappear randomly.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
As when running with jdk20+24 or older: no random line should appear when zooming in or out in the application.
ACTUAL -
Random lines, some being segments, other longer straight lines, appear on boarder of curves. They look like being tangent.

CUSTOMER SUBMITTED WORKAROUND :
None.

FREQUENCY : always