html5: faster network layer, input devices, etc

[totaam]

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 html5 client improvements: refactoring, mpeg4, scrolling, etc #1341#comment:12)
• less wasteful process_xxxx_queue" timers scheduling
• process_receive_queue should not use recursion

Input devices:

• throttle tablet input events / osx trackpad sends too many events with HTML5 client #1390

[totaam]

2017-02-28 13:13:57: antoine uploaded file test-slow-send.patch (0.6 KiB)

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

[totaam]

2017-02-28 13:15:20: antoine uploaded file html5-zerocopy.patch (7.9 KiB)

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

[totaam]

2017-02-28 15:32:31: antoine uploaded file html5-timers-managed.patch (2.9 KiB)

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

[totaam]

2017-02-28 15:48:40: antoine uploaded file html5-timers-managed-v2.patch (1.9 KiB)

alternative implementation of managed timers

[totaam]

2017-02-28 16:07:21: antoine changed status from new to assigned

[totaam]

• 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.

[totaam]

2017-03-05 17:46:59: antoine uploaded file html5-clipboard.patch (10.3 KiB)

two-way clipboard

[totaam]

• 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

[totaam]

• video support moved to #1463. (too late for this release)
• tablet input device is ready: osx trackpad sends too many events with HTML5 client #1390#comment:1

@afarr: since we don't have a reliable way of measuring performance, I'm not sure there's anything here for you to test - feel free to close as FYI. (just bear in mind that the scrolling paint code still looks buggy with the html5 client: #1432?)

[totaam]

• r15275 fixes scroll paint (15277 for v1.0.x)
• r15276 adds "paint box" debugging, enabled with debug mode (same code and colors as debug option for subregion color coding according to encodings, quality, speed, etc? #760 "XPRA_OPENGL_PAINT_BOX")