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 event. ++ ---- [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 `''''''` and `''''''`, 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 `''''''` and `''''''`, 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 `''''''` (and `''''''`) 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.