html5: faster network layer, input devices, etc

[Antoine Martin]

Follow up from #1341.

Video / paint:

• either fix broadway, or get native video decoding to play properly without buffering too much
• process_interval should not be hardcoded?

Network layer:

• onmessage should not copy bytes at a time (see ticket:1341#comment:12)
• less wasteful process_xxxx_queue" timers scheduling
• process_receive_queue should not use recursion

Input devices:

• throttle tablet input events / #1390

[Antoine Martin]

make it easier to test slow network and packet aggregation in client receiver code

[Antoine Martin]

implement zero copy in network layer - only aggregate chunks if we have to, do it using fast set method

[Antoine Martin]

try to manage the timers and only use them as needed - actually makes things slower

[Antoine Martin]

alternative implementation of managed timers

[Antoine Martin]

• r15183 merges the zero copy code (and removes some unused variables, more removed in r15185)
• r15184: don't queue draws, r15187: lower timer delay

We could also modify process_receive_queue to only parse the "packet size", "packet flags" and "padding" when we get the full 8-byte header - small saving which would make the code harder to read. meh.

With these changes, testing with glxspheres at high res, the throughput and framerate are increased - but really not by much. And this is even more wasteful than before (running the timers at full speed), so r15188 switches to "on-demand" timers. (also a bit slower?)

Big question: how can we validate those changes better? We need reliable performance data to compare before and after, preferably using a real-world use case (not glxgears / glxspheres).. As some of these changes may actually make things worse.

[Antoine Martin]

two-way clipboard

[Antoine Martin]

• moving clipboard to its own ticket: #1461
• we try to clamp the windows to the browser's window area, but allow the user to move part of the window "off-screen" if they wish: r15241 - but there's a bug in the "draggable window" code, which is reporting coordinates out of range... and they get more and more out of range as we clamp the window, something is not getting updated somewhere

[Antoine Martin]

I am moving video support to #1463. (too late for this release)

Tablet devices should be handled better than before as of r15253 + r15255.
We normalize the wheel event values using the facebook code found here: ​normalizeWheel.js. And we try to send one event for each javascript wheel event we receive, unless those are very fine grained (from a tablet?).

With debug enabled, the Javascript console shows that on Linux I'm getting a delta of 120 per event with Firefox, and ~156 for google chrome..
We'll be able to handle this a lot better once we implement extended input device support (#173)

Links:

• ​javascript wheel events documentation
• ​wheel delta test page

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@afarr: since we don't have a reliable way of measuring performance, the only thing to test in this ticket is likely to be the scrolling with various browsers / os / devices.

[Antoine Martin]

• r15275 fixes scroll paint (r15277 for v1.0.x)
• r15276 adds "paint box" debugging, enabled with debug mode (same code and colors as #760 "XPRA_OPENGL_PAINT_BOX")

[J. Max Mena]

Noted and closing.

[migration script]

this ticket has been moved to: ​https://github.com/Xpra-org/xpra/issues/1424