Unify cmd packages?

[BigJk]

Currently there is

• /cmd/headless
  • Simple headless version without any native dependencies. It's just go and can be cross-compiled to any target OS from any other OS.
• /cmd/headless-libusb
  • Headless version with native dependency (libusb) for direct printing over USB.
• /cmd/windows-direct
  • Electron window + Windows syscalls for direct printing on Windows.

After adding libusb I think it's a good time to rethink this approach. Maybe you are using MacOSX and still want to have a electron window and libusb. Currently that is not covered by these 3 packages.

In Go it's possible to activate and deactivate features based on OS or tags that can be specified while building. I think this would be a better solution than separate packages and would allow users to mix and match what they need.

My Idea

• Remove /cmd/headless /cmd/headless-libusb and /cmd/windows-direct
• The main.go will be moved to /cmd/main.go
• Without specifying any tags main.go will be the normal headless version without any native dependencies
• On windows the windows direct printing will be automatically enabled because it only requires syscalls and no native dependencies that need to be compiled. So there is no downside to just activating it when OS == windows

Optional Tags

• LIBUSB will enable usb printing and require libusb-1.0 to be installed
• ELECTRON will enable a electron window where the frontend is shown

Example

headless without libusb or electron window

cd /somewhere/.../snd/cmd
go build

libusb

cd /somewhere/.../snd/cmd
go build -tags="LIBUSB"

libusb + electron

cd /somewhere/.../snd/cmd
go build -tags="LIBUSB ELECTRON"

This also would help to keep it more DRY because the 3 packages currently all contain the same main() function with just minor changes.

I pushed it to a seperate branch so feel free to take a look at it cmd-unify/cmd. If there are no objections I will merge it into master.

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Just a little info for anybody that is not familiar with go. The init() function of a file will be executed before the main function. This can be combined with the build tags / constraints to enable or remove stuff depending on the tags or OS.

init(): https://golang.org/doc/effective_go.html#init build constraints: https://golang.org/pkg/go/build/

[BigJk]

Merged 91b892f45d6cf4b7420fa0b8bffc1ef843ae120a