Add support for setting scale factor from parameters

[andreadaoud]

This adds support for manually specifying dpi scale factor. --force-scale-factor argument is added to examples to set factor. Tested on wayland.

[andreadaoud]

I have no problem to contribute all my code to flutter.

[HidenoriMatsubayashi]

@andreadaoud

I don't know if this change will be included in future contributions to flutter/engine, but is it okay to delegate all rights related to this change to us (Sony)? If you agree with the above, please add the Developer Certificate of Origin (DCO).

[andreadaoud]

Yes, I'm willing to do so, but could you please point out how to do it?

[HidenoriMatsubayashi]

See https://www.secondstate.io/articles/dco/

[andreadaoud]

@HidenoriMatsubayashi DCO is added, thanks for your guide. However, I cannot get the code formatting correctly, could you please help me?

[HidenoriMatsubayashi]

Run find src/flutter/shell/platform/linux_embedded/ -iname *.h -o -iname *.cc | xargs clang-format --dry-run --Werror
src/flutter/shell/platform/linux_embedded/window/elinux_window_x11.cc:26:19: error: code should be clang-formatted [-Wclang-format-violations]
  current_scale_ = 
                  ^
src/flutter/shell/platform/linux_embedded/window/elinux_window_wayland.cc:833:19: error: code should be clang-formatted [-Wclang-format-violations]
  current_scale_ =
                  ^
src/flutter/shell/platform/linux_embedded/window/elinux_window_drm.h:37:21: error: code should be clang-formatted [-Wclang-format-violations]
    current_scale_ = 
                    ^

Can you try to clang-format?

$ clang-format -i src/flutter/shell/platform/linux_embedded/window/elinux_window_x11.cc
$ clang-format -i src/flutter/shell/platform/linux_embedded/window/elinux_window_wayland.cc
$ clang-format -i src/flutter/shell/platform/linux_embedded/window/elinux_window_drm.h

[andreadaoud]

I don't know why, but running clang-format check locally results in errors that does not belong to my code.

find src/flutter/shell/platform/linux_embedded/ -iname *.h -o -iname *.cc | xargs clang-format --dry-run --Werror
src/flutter/shell/platform/linux_embedded/flutter_elinux_view.cc:304:32: error: code should be clang-formatted [-Wclang-format-violations]
      mouse_state_.buttons == 0
                               ^
src/flutter/shell/platform/linux_embedded/flutter_elinux_view.cc:305:47: error: code should be clang-formatted [-Wclang-format-violations]
          ? mouse_state_.flutter_state_is_down ? FlutterPointerPhase::kUp
                                              ^
src/flutter/shell/platform/linux_embedded/flutter_elinux_view.cc:305:74: error: code should be clang-formatted [-Wclang-format-violations]
          ? mouse_state_.flutter_state_is_down ? FlutterPointerPhase::kUp
                                                                         ^
src/flutter/shell/platform/linux_embedded/flutter_elinux_view.cc:306:77: error: code should be clang-formatted [-Wclang-format-violations]
                                               : FlutterPointerPhase::kHover
                                                                            ^
src/flutter/shell/platform/linux_embedded/flutter_elinux_view.cc:307:76: error: code should be clang-formatted [-Wclang-format-violations]
          : mouse_state_.flutter_state_is_down ? FlutterPointerPhase::kMove

[HidenoriMatsubayashi]

Hmm, but the remain errors are below:

src/client_wrapper/flutter_view_controller.cc:37:41: error: code should be clang-formatted [-Wclang-format-violations]
  c_view_properties.force_scale_factor =
                                        ^
src/client_wrapper/flutter_view_controller.cc:39:35: error: code should be clang-formatted [-Wclang-format-violations]
  c_view_properties.scale_factor =

[andreadaoud]

@HidenoriMatsubayashi CI has passed, thank you.

BTW, currently I have tested this on standalone launcher, but I'm not sure how to integrate changed code into my app, to let it build directly (that is, make flutter-elinux directly use the changed code). Could you please give me a little clue? Thanks a lot!

[HidenoriMatsubayashi]

Thanks a lot.

You can build libflutter_elinux_{wayland|gbm|eglstream|x11}.so with this step in https://github.com/sony/flutter-embedded-linux/wiki/Building-Embedded-Linux-embedding-for-Flutter#build-shared-library-for-flutter-elinux. After building it, copy it to `<path_to_install>/flutter-elinux/flutter/bin/cache/artifacts/engine/elinux--/libflutter_elinux_*.so