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See also Gecko:CrossProcessLayers.

Pre-Fennec work

  • "shadow" layer trees (parent's reference to a child's tree) hooked into frame or widget code; currently they're only hooked into testing code. We need to associate TabChilds' shadow layer trees with their frames/widgets in the browser process.
  • BasicThebesLayer pixel data shared efficiently with its BasicShadowThebesLayer (needed for realistic performance testing)

Fennec-specific work

cedar/mobile2 --> m-c/m-b merge blockers

cedar merged to m-c, but we can't make meaningful further progress without


2.0 b1 TODO


  • bug 595403 can't scroll up after resize/orientation change
  • double clicking many times on desktop gives strange results
  • sometimes url bar comes up on double clicking a lot
  • (no bug) repeated taps on the scroll wheel (desktop) or volume rocker (maemo) cause incorrect zooming - a problem when a new event happens during an in-progress animation?


  • bug 591555 crashy in shadow layers
  • bug 593243 invalidation of content outside the CSS viewport but inside the displayport is ignored
  • (no bug) fix seaming, at least for simple cases (v. @ 2.0 or 0.5 scale-zoom)
  • shadow layers perf work
    • (no bug) smarter allocation of ThebesLayer backing buffers
    • retained-content-only layer transactions
  • (possibly) bug 594847 handle content-process crashes more gracefully

2.0 b1 nice-to-have

  • hacky slow fallback path for scrolling subframes (e.g. mobile gmail), only on pages with scrollable subframes
  • bug 593310 draw a "checkerboard" or other indicator over waiting-to-be-filled regions
  • (no bug) make CanvasLayer paint directly into shareable surfaces, remove third buffer
  • don't draw the caret in the content process
  • panning XUL documents (e.g. about:config) - might be covered by the subframe scrolling path
  • bug 597081 - zooming in non-remote tabs

2.0 musts

  • compositing Basic*Layer tree published by content, using GL/EGL in the browser process
  • HW-accelerated video that bypasses content-process main thread
  • fast scrolling of subframes
  • better support for position:fixed elements
  • WebGL? proxied?
  • fast plugin drawing? that bypasses content-process main thread?

Questions that come with using browser element

  • Where does panning and kinetic panning live?
    • Ben: hopefully as javascript in browser binding
  • Where will handling of zoom metadata live?
  • Where will the tap => element code live (including better link clicking and transforming coordinates for zoom level)?
  • Where does double-tap to zoom live?
  • Where does double-click simulation live? Nokia devices didn't support a native double click event. Maybe we still need to do some form of event re-dispatching to browser elements.
  • Where does tap highlighting live? I think webkit has a tap-highlight-color CSS property.

Other questions

  • What is the proper behavior for position: fixed elements when there is an additional displayport on top of the CSS viewport?
    • what do other browsers with displayport-type things do?
      • MicroB fixes wrt displaport, hides on pan, shows when pan finishes
      • mobilesafari appears to basically ignore position:fixed wrt displayport


hg clone
cd cedar
hg clone mobile

From there, a normal opt or debug build will work.


To get function timer data from a function-timer enabled build on android

adb shell am start -a org.mozilla.fennec -n org.mozilla.fennec/org.mozilla.fennec.App --es env0 MOZ_FT=/data/data/org.mozilla.fennec/log.txt
adb shell cat /data/data/org.mozilla.fennec/log.txt

adb pull [log] should work as well.