[win32] MouseEnter not fired on fast traversals

[DanskerDave]

This Problem was first reported over 7 years ago for SWT 4.11 here:

18 Months ago I again verified the Issue still exists on SWT 4.19.

MouseEnter events are sometimes not being fired (or are being lost)
The attached program highlights this.

Traversing as fast as possible with the mouse from left of the window to right of the window fires MouseEnter & MouseExit for all 3 Canvases (see Console).

The 3 Canvases do not overlap, in fact there is a gap between them.

Traversing very fast between, say, the Red & Green Canvases, (only sometimes) the MouseEnter event is not fired. Optically noticable due to the Arrow Cursor.
(normally after entering, the Hand Cursor is shown)

This can also be verified in the Console log.

The MouseExit event seems always to fire.

Attachments:

Example Program highlighting the problem
An updated snippet which prints in console only when there's an error.
Refined Snippet
Revised Snippet to run under SWT v4.11

Environment:

1. Select the platform(s) on which the behavior is seen:

• • All OS
• • Windows
• • Linux
• • macOS

2. Additional OS info (e.g. OS version, Linux Desktop, etc)
   Java Version for Eclipse & Project is 1.8.0_51 64 bit.

Version since
4.11 (& later also verified on 4.19)

[DanskerDave]

Problem still persists.
Verified using the SWT v3.122 bundled with Eclipse v4.26 (2022-12)

[tmssngr]

Did you verify whether the event is sent by Windows, but got lost in SWT?

[DanskerDave]

I'm afraid when it comes to Windows I'm just a humble user, so I don't know.

Back in 2017, Niraj Modi of IBM took a look at this. But I never heard whether he made any headway.
https://projects.eclipse.org/user/2612

P.S. I forgot to Link to the original Issue in Eclipse:
https://bugs.eclipse.org/bugs/show_bug.cgi?id=482022

[jukzi]

If the mouse is moved very fast it might be that not all intermediate positions are reported by the Mouse or OS. The application then can not decide if the mouse path took the way directly from the old position to the new position or if the mouse was moved around the window.
@DanskerDave unless somebody proves that mouse events get lost and contributes a fix this issue will not be handled.