Control batch delay for video regions

[Scott Bennett]

Similar to #1077 (manually control batch delay at runtime) this would allow for the batch delay for video regions to be set independently of non-video regions

[Antoine Martin]

The main batch delay drives everything, starting with the timers, and so adding a separate delay would conflict with that: we would have two timers firing independently... but they also need to cooperate as we send screen updates bundled up together as much as we can, even with video regions.

Unless we make this new video region batch delay a multiple of the other one, then a lot of the code would need to be duplicated. And even then, the "main" batch delay is adjusted automatically.. so we can't guarantee that a multiple would give us a fixed value either.

Changing the video refresh rate would also affect the main batch delay.

Then there's also the issue that we may want the video (or client vrefresh rate, or a combination of the two) to drive the video refresh rate to be able to handle the optimal framerate and not miss any frames (vsync and not tearing).

Finally, since this request is driven by client decode speed constraints, the adjustments should be automatic: the client already tells the server how long it takes to decode each frame and this should be the value we use to calculate the video batch delay.

[Antoine Martin]

See also: #1135.

[Antoine Martin]

I think there are too many conflicts with other features: #1257, #981, etc.

Maybe we can think of another way to achieve the same results? (new ticket)

[Antoine Martin]

Things have changed quite a bit since this ticket was created (in particular #800 and #1135), let's create a new ticket with new requirements when we have them,

[migration script]

this ticket has been moved to: ​https://github.com/Xpra-org/xpra/issues/1130