mouse wheel in 8.7

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It appears that Tk 8.7a5 on linux has different processing of mouse wheel events from 8.6. On 8.6 and previous, rotating the wheel produces a ButtonPress 4 or 5 event, depending on direction of rotation. This no longer happens in 8.7a5.
Is this an intentional change or a bug?
Is there a list somewhere of changes in 8.7 relative to 8.6?

2022-07-21:
Hi, you can now bind against <MouseWheel> event.
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[Csaba Nemethi] 2022-07-21: Most of the changes related to the processing of mouse wheel events in Tk 8.7 were proposed in https://core.tcl-lang.org/tips/doc/trunk/tip/474.md%|%TIP 474%|%. According to this specification, in Tk 8.7a5 and later the set of mouse wheel events is the same on all windowing systems:

   * The mouse wheel events along the vertical axis are `'''<MouseWheel>'''` and `'''<Option-MouseWheel>'''`, where the `'''Option'''` modifier is bound to the `Option` key on Mac OS X/11+ and to the `Alt` key on Windows and X11.
   
   * The mouse wheel events along the horizontal axis are `'''<Shift-MouseWheel>'''` and `'''<Shift-Option-MouseWheel>'''`, where the `'''Option'''` modifier is bound to the `Option` key on Mac OS X/11+ and to the `Alt` key on Windows and X11. In these Tk versions, left/right tilting the scroll wheel of a mouse having one or two additional (thumb) buttons gives rise to `'''<Shift-MouseWheel>'''` (and `'''<Shift-Option-MouseWheel>'''`) events on all windowing systems.

In addition, in Tk 8.7a5 and later a mouse wheel tick now scrolls a listbox, ttk::treeview, tablelist, etc. by 3 units, on all windowing systems. Together with the key corresponding to the `'''Option'''` modifier, it scrolls by 10 units.