Latency for many GUI operations

[twinbee]

This issue has been discussed (and opened by me) on the thread at: ​https://www.haiku-os.org/community/forum/latency_haiku_gui_interaction_and_general_first_thoughts

Please read that for the fuller picture (including my last post, and other peoples' comments), but generally, where possible, it would nice to use mouseclick-down rather than mouseclick-down-up for many GUI operations (excluding cases where dragging is used). The latency would be improved as a result (about 40-100ms), and I think that fits well with the Haiku philosophy.

[diver]

See also #6978.

[leavengood]

Taking ownership as I'll probably experiment with this before stippi.

[axeld]

Whatever you come up with, please try to keep it consistent. While one could in theory always use mouse-down where no dragging is possible, in practice, this would not be a viable solution because of this.

[diver]

There is also a delay before menu opens. See hrev24193.

[leavengood]

I think those delays are needed for the diagonal submenu code to work right (and that is a necessary feature, especially with the Tracker context-menu navigation), but I think the delays could be experimented with. The 1 second navigation area timeout is way too long IMO.