Replace channel list TreeView with ListView

This migrates gtkcord4's channels list from the deprecated GtkTreeView
API to the newer GtkListView API, which looks far better and is much
less buggy.

Fixes #208.
Fixes #196.

internal/gtkcord/handler.go

@@ -0,0 +1,36 @@
+package gtkcord
+
+import (
+	"github.com/diamondburned/arikawa/v3/utils/handler"
+	"github.com/diamondburned/gotk4/pkg/core/glib"
+)
+
+// MainThreadHandler wraps a [handler.Handler] to run all events on the main
+// thread.
+type MainThreadHandler struct {
+	h *handler.Handler
+}
+
+// NewMainThreadHandler creates a new MainThreadHandler.
+func NewMainThreadHandler(h *handler.Handler) *MainThreadHandler {
+	hh := &MainThreadHandler{h: handler.New()}
+	h.AddSyncHandler(func(ev any) {
+		glib.IdleAddPriority(glib.PriorityDefault, func() {
+			hh.h.Call(ev)
+		})
+	})
+	return hh
+}
+
+// AddHandler adds a handler to the handler.Handler.
+// The given handler will be called on the main thread.
+// The returned function will remove the handler.
+func (h *MainThreadHandler) AddHandler(handler any) func() {
+	return h.h.AddSyncHandler(handler)
+}
+
+// AddSyncHandler is the same as [AddHandler].
+// It exists for compatibility.
+func (h *MainThreadHandler) AddSyncHandler(handler any) func() {
+	return h.h.AddSyncHandler(handler)
+}

internal/gtkcord/state.go

@@ -70,6 +70,7 @@ const (
 
 // State extends the Discord state controller.
 type State struct {
+	*MainThreadHandler
 	*ningen.State
 }
 
@@ -110,9 +111,10 @@ func Wrap(state *state.State) *State {
 	}
 
 	// dumpRawEvents(state)
-
+	ningen := ningen.FromState(state)
 	return &State{
-		State: ningen.FromState(state),
+		MainThreadHandler: NewMainThreadHandler(ningen.Handler),
+		State:             ningen,
 	}
 }
 
@@ -157,9 +159,9 @@ func InjectState(ctx context.Context, state *State) context.Context {
 
 // WithContext creates a copy of State with a new context.
 func (s *State) WithContext(ctx context.Context) *State {
-	return &State{
-		State: s.State.WithContext(ctx),
-	}
+	s2 := *s
+	s2.State = s.State.WithContext(ctx)
+	return &s2
 }
 
 // BindHandler is similar to BindWidgetHandler, except the lifetime of the

internal/icons/gtkcord4.gresource.xml

@@ -25,5 +25,9 @@
     <file preprocess="xml-stripblanks" alias="user-invisible-symbolic.svg">scalable/actions/user-invisible-symbolic.svg</file>
     <file preprocess="xml-stripblanks" alias="user-offline-symbolic.svg">scalable/actions/user-offline-symbolic.svg</file>
     <file preprocess="xml-stripblanks" alias="user-status-pending-symbolic.svg">scalable/actions/user-status-pending-symbolic.svg</file>
+    <file preprocess="xml-stripblanks" alias="channel-symbolic.svg">scalable/actions/channel-symbolic.svg</file>
+    <file preprocess="xml-stripblanks" alias="channel-voice-symbolic.svg">scalable/actions/channel-voice-symbolic.svg</file>
+    <file preprocess="xml-stripblanks" alias="channel-broadcast-symbolic.svg">scalable/actions/channel-broadcast-symbolic.svg</file>
+    <file preprocess="xml-stripblanks" alias="thread-branch-symbolic.svg">scalable/actions/thread-branch-symbolic.svg</file>
   </gresource>
 </gresources>

internal/icons/icons.go

@@ -19,6 +19,5 @@ func init() {
 	if err != nil {
 		log.Panicln("Failed to create resources: ", err)
 	}
-
 	gio.ResourcesRegister(resources)
 }