Expose GLFW window focus callback via option

[geoah]

I needed a way to detect whether the window got in or out of focus in order to enable/disable notifications, re-check connections and other things, so I wanted to expose the GLFW SetFocusCallback method.

Please let me know if there is a better way of doing this or feel free to close the PR if you are not interested in merging something like this.

Thank you :)

[geoah]

I'm also interested in exposing window.SetDropCallback to allow drag-dropping so any ways to improve the way we expose GLFW callbacks would be appreciated.

[pchampio]

Such feature are already exposed through wiki: GLFWPlugins

[pchampio]

option.go

package main

import (
	"github.com/go-flutter-desktop/go-flutter"
	"github.com/go-flutter-desktop/go-flutter/plugin"
	"github.com/go-gl/glfw/v3.3/glfw"
)

var options = []flutter.Option{
	flutter.WindowInitialDimensions(400, 300),
	flutter.AddPlugin(&FocusCallback{}),
}

// FocusCallback is a GLFWplugin
type FocusCallback struct {
	channel *plugin.MethodChannel
}

var _ flutter.Plugin = &FocusCallback{}     // compile-time type check
var _ flutter.PluginGLFW = &FocusCallback{} // compile-time type check
// FocusCallback struct must implement InitPlugin and InitPluginGLFW

// InitPlugin creates a MethodChannel for "samples.go-flutter.dev/focus"
func (p *FocusCallback) InitPlugin(messenger plugin.BinaryMessenger) error {
	p.channel = plugin.NewMethodChannel(messenger, "samples.go-flutter.dev/focus", plugin.StandardMethodCodec{})
	return nil
}

// InitPluginGLFW is used to gain control over the glfw.Window
func (p *FocusCallback) InitPluginGLFW(window *glfw.Window) error {
	window.SetFocusCallback(func(_ *glfw.Window, focused bool) {
		p.channel.InvokeMethod("push/focus", map[interface{}]interface{}{
			"focused": focused,
		})
	})
	return nil
}

Dart code:

  const platform_channel_draggable =
      MethodChannel('samples.go-flutter.dev/focus');
  platform_channel_draggable
      .setMethodCallHandler((MethodCall methodCall) async {
    if (methodCall.method == "push/focus") {
      print("Focused: " + methodCall.arguments["focused"].toString());
    }
  });

[pchampio]

Another example for window.SetDropCallback:

option.go:
(golang []string needs to be converted to []interface{} more info here)

package main

import (
	"github.com/go-flutter-desktop/go-flutter"
	"github.com/go-flutter-desktop/go-flutter/plugin"
	"github.com/go-gl/glfw/v3.3/glfw"
)

var options = []flutter.Option{
	flutter.WindowInitialDimensions(400, 300),
	flutter.AddPlugin(&FocusCallback{}),
}

// FocusCallback is a plugin that makes moving the bordreless window possible
type FocusCallback struct {
	channel *plugin.MethodChannel
}

var _ flutter.Plugin = &FocusCallback{}     // compile-time type check
var _ flutter.PluginGLFW = &FocusCallback{} // compile-time type check
// FocusCallback struct must implement InitPlugin and InitPluginGLFW

// InitPlugin creates a MethodChannel for "samples.go-flutter.dev/draggable"
func (p *FocusCallback) InitPlugin(messenger plugin.BinaryMessenger) error {
	p.channel = plugin.NewMethodChannel(messenger, "samples.go-flutter.dev/glfw", plugin.StandardMethodCodec{})
	return nil
}

// InitPluginGLFW is used to gain control over the glfw.Window
func (p *FocusCallback) InitPluginGLFW(window *glfw.Window) error {
	window.SetFocusCallback(func(_ *glfw.Window, focused bool) {
		p.channel.InvokeMethod("push/focus", map[interface{}]interface{}{
			"focused": focused,
		})
	})
	window.SetDropCallback(func(_ *glfw.Window, names []string) {
		//converting a []string to a []interface{}
		y := make([]interface{}, len(names))
		for i, v := range names {
			y[i] = v
		}
		p.channel.InvokeMethod("push/drop", map[interface{}]interface{}{
			"drop": y,
		})
	})
	return nil
}

dart:

  const platform_channel_draggable =
      MethodChannel('samples.go-flutter.dev/glfw');
  platform_channel_draggable
      .setMethodCallHandler((MethodCall methodCall) async {
    if (methodCall.method == "push/focus") {
      print("Focused: " + methodCall.arguments["focused"].toString());
    }
    if (methodCall.method == "push/drop") {
      print("dropped: " + methodCall.arguments.toString());
    }
  });

[geoah]

@pchampio thank you, sorry I'm totally blind. :D