new-gui/plugin.go

package gui

// This is based off of the excellent example and documentation here:
// https://github.com/vladimirvivien/go-plugin-example
// There truly are great people in this world.
// It's a pleasure to be here with all of you

import (
	"os"
	"plugin"

	"git.wit.org/wit/gui/toolkit"
)

var err error
type Symbol any

type aplug struct {
	// Ok bool
	name string
	filename string
	plug *plugin.Plugin
	sym *plugin.Symbol
	LoadOk bool
	InitOk bool
	MainOk bool

	Init func()
	// TODO: make Main() main() and never allow the user to call it
	// run plugin.Main() when the plugin is loaded
	Main func(func ())	// this never returns. Each plugin must have it's own goroutine
	Queue func(func ())	// Should this return right away? Should it wait (can it wait?)
	Quit func()
	// NewWindow func(*toolkit.Widget)

	// simplifies passing to the plugin
	Send func(*toolkit.Widget, *toolkit.Widget)
}

var allPlugins []*aplug

// loads and initializes a toolkit (andlabs/ui, gocui, etc)
func LoadToolkit(name string) bool {
	var newPlug aplug

	log(debugGui, "gui.LoadToolkit() START")
	newPlug.LoadOk = false

	for _, aplug := range allPlugins {
		log(debugGui, "gui.LoadToolkit() already loaded toolkit plugin =", aplug.name)
		if (aplug.name == name) {
			log(debugGui, "gui.LoadToolkit() SKIPPING")
			return true
		}
	}

	// locate the shared library file
	filename := name + ".so"
	loadPlugin(&newPlug, filename)
	if (newPlug.plug == nil) {
		log(true, "attempt to find plugin", filename, "failed")
		return false
	}
	// newPlug.Ok = true
	newPlug.name = name

	// deprecate Init(?)
	newPlug.Init = loadFuncE(&newPlug, "Init")

	// should make a goroutine that never exits
	newPlug.Main  = loadFuncF(&newPlug, "Main")

	// should send things to the goroutine above
	newPlug.Queue = loadFuncF(&newPlug, "Queue")

	// unload the plugin and restore state
	newPlug.Quit = loadFuncE(&newPlug, "Quit")

	// Sends a widget (button, checkbox, etc) and it's parent widget
	// This includes instructions like "Add", "Delete", "Disable", etc
	newPlug.Send = loadFunc2(&newPlug, "Send")

	allPlugins = append(allPlugins, &newPlug)

	log(debugPlugin, "gui.LoadToolkit() END", newPlug.name, filename)
	newPlug.Init()
	newPlug.LoadOk = true
	return true
}

// TODO: All these functions need to be done a smarter way
// but I haven't worked out the golang syntax to make it smarter
func loadFuncE(p *aplug, funcName string) func() {
	var newfunc func()
	var ok bool
	var test plugin.Symbol

	test, err = p.plug.Lookup(funcName)
	if err != nil {
		log(debugGui, "DID NOT FIND: name =", test, "err =", err)
		return nil
	}

	newfunc, ok = test.(func())
	if !ok {
		log(debugGui, "function name =", funcName, "names didn't map correctly. Fix the plugin name =", p.name)
		return nil
	}
	return newfunc
}

func loadFunc2(p *aplug, funcName string) func(*toolkit.Widget, *toolkit.Widget) {
	var newfunc func(*toolkit.Widget, *toolkit.Widget)
	var ok bool
	var test plugin.Symbol

	test, err = p.plug.Lookup(funcName)
	if err != nil {
		log(debugGui, "DID NOT FIND: name =", test, "err =", err)
		return nil
	}

	newfunc, ok = test.(func(*toolkit.Widget, *toolkit.Widget))
	if !ok {
		log(debugGui, "function name =", funcName, "names didn't map correctly. Fix the plugin name =", p.name)
		return nil
	}
	return newfunc
}

// This is probably dangerous and should never be done
// executing arbitrary functions will cause them to run inside the goroutine that
// the GUI toolkit itself is running in. TODO: move to channels here
func loadFuncF(p *aplug, funcName string) func(func ()) {
	var newfunc func(func ())
	var ok bool
	var test plugin.Symbol

	test, err = p.plug.Lookup(funcName)
	if err != nil {
		log(debugGui, "DID NOT FIND: name =", test, "err =", err)
		return nil
	}

	newfunc, ok = test.(func(func ()))
	if !ok {
		log(debugGui, "function name =", funcName, "names didn't map correctly. Fix the plugin name =", p.name)
		return nil
	}
	return newfunc
}

/*
	This searches in the following order for the plugin .so files:
		./toolkit/
		~/go/src/go.wit.org/gui/toolkit/
		/usr/lib/go-gui/
*/
func loadPlugin(p *aplug, name string) {
	var filename string

	homeDir, err := os.UserHomeDir()
	if err != nil {
		exit(err)
	}

	// attempt to write out the file from the internal resource
	filename = "toolkit/" + name
	p.plug = loadfile(filename)
	if (p.plug != nil) {
		p.filename = filename
		return
	}

	filename = homeDir + "/go/src/git.wit.org/wit/gui/toolkit/" + name
	p.plug = loadfile(filename)
	if (p.plug != nil) {
		p.filename = filename
		return
	}

	filename = "/usr/lib/go-gui/" + name
	p.plug = loadfile(filename)
	if (p.plug != nil) {
		p.filename = filename
		return
	}
	return
}

// load module
// 1. open the shared object file to load the symbols
func loadfile(filename string) *plugin.Plugin {
	plug, err := plugin.Open(filename)
	if err != nil {
		log(debugGui, "plugin FAILED =", filename, err)
		return nil
	}
	log(debugGui, "plugin WORKED =", filename)
	log(true, "loading plugin", filename, "worked")
	return plug
}

// Sends a widget and what to do with it to the plugin
// parent = n, child = c
func send(p *Node, c *Node) {
	for _, aplug := range allPlugins {
		log(debugPlugin, "Send() aplug =", aplug.name, "type=", c.widget.Type, "action=", c.widget.Action, "name=", c.widget.Name)
		if (aplug.Send == nil) {
			log(debugPlugin, "\tSend() failed (aplug.Selete = nil) for", aplug.name)
			continue
		}
		aplug.Send(&c.parent.widget, &c.widget)
	}
}