Tracking issue: OpenHarmony port

[jschwe]

As of #32594 servoshell now supports OpenHarmony, and the respective build is also tested in CI. However, there are also still a number of issues, and this tracking issues serves the purpose of giving an overview over the remaining issues. The issues listed here are currently not sorted in any particular order.

• [x] Update the servo documentation with instructions on how to build servo for OpenHarmony. Update: Documentation now available at https://book.servo.org/hacking/building-for-openharmony.html
• [x] Redirect stdout/stderr to hilog (see android logcat redirection, perhaps we can unify the implementation): PR https://github.com/servo/servo/pull/32858
• [ ] Improved font support: See issue https://github.com/servo/servo/issues/32723
• [x] WebGL: WebGL currently needs to be turned off, since offscreen surface support for ohos is not implemented yet in surfman. Fixed in https://github.com/servo/surfman/pull/310
• [ ] Window resizing: We currently do nothing on the callback, so the current behavior is the rendered image gets stretched / shrunk to fit the new actual size of the window.
• [ ] IPC-channel cross-process support. OH 4.1+ adds shm_open support, but at runtime the shm_open / memfd calls in ipc_channel fails. Needs investigation on what the error code is, and what we can do about it.
• [ ] Vsync: Probably updates should be batched and processed based on the vertical synchronization signal. This is likely a pre-requiste for Fling support. Without fling, the input touch event notifications probably serve as a poor-mans vsync signal when scrolling. (PR https://github.com/servo/servo/pull/33117)
  • [ ] Animation updates should happen based on the vsync signal on ohos. Probably should be solved as part of https://github.com/servo/servo/issues/3406
• [x] Add a back button, forward button (https://github.com/servo/servo/pull/33206)
• [ ] Input Events / Gestures:
  • [ ] Fling support (note: On android fling only seems to work in the "up" direction, but not downwards, so perhaps we can do something shared here)
  • [ ] Keyboard events (probably low priority for now)
  • [ ] Mouse Events (Mouse, Touchpad)
  • [ ] Implement callback to bring up / hide IME.
• [ ] Support configuring initialization parameters via some method, e.g. from a configuration file.
• [ ] Reading files on OH: Apps are sandboxed. Apps support shipping files via rawfile and resfile methods. rawfile requires that code interacts with the file using specialised rawfile APIs. Resfile files should appear in the sandboxed area, after the app is installed, but that didn't seem to work for me on first try.
• [ ] Move the ArkTS ServoDemo app to the support folder in servo and integrate the .hap build into mach or a different tool, which could wrap the whole ohos app build , sign and flash process.
• [ ] Run the Ohos app in the emulator in CI. This is blocked on either the HarmonyOS NEXT emulator becoming publicly available, or figuring out how to run pure OpenHarmony on qemu.
• [ ] Upstream webrender patch https://github.com/servo/webrender/pull/4856
• [ ] Add OpenHarmony support to wgpu.

[Taym95]

@jschwe I may be able to help here. How do you test your changes? Do you run OpenHarmony in an emulator?

[jschwe]

@Taym95 Thanks for the interest! I mostly test on real hardware, but I've also used the HarmonyOS emulator to test my changes. However, that emulator is not publicly available yet - but we hope the emulator will be made generally available soon. I will post an update here, once that is the case.