feat(tracker, gioui): add confirmation dialogs before quit/new/load song

This should avoid accidentally losing all work by destroying window.

tracker/gioui/layout.go

@@ -3,6 +3,7 @@ package gioui
 import (
 	"image"
 
+	"gioui.org/app"
 	"gioui.org/layout"
 	"gioui.org/op/clip"
 	"gioui.org/op/paint"
@@ -20,6 +21,62 @@ func (t *Tracker) Layout(gtx layout.Context) {
 	t.Alert.Layout(gtx)
 	dstyle := ConfirmDialog(t.Theme, t.ConfirmInstrDelete, "Are you sure you want to delete this instrument?")
 	dstyle.Layout(gtx)
+	dstyle = ConfirmDialog(t.Theme, t.ConfirmSongDialog, "Do you want to save your changes to the song? Your changes will be lost if you don't save them.")
+	dstyle.ShowAlt = true
+	dstyle.OkStyle.Text = "Save"
+	dstyle.AltStyle.Text = "Don't save"
+	dstyle.Layout(gtx)
+	for t.ConfirmSongDialog.BtnOk.Clicked() {
+		if t.SaveSongFile() {
+			t.confirmedSongAction()
+		}
+		t.ConfirmSongDialog.Visible = false
+	}
+	for t.ConfirmSongDialog.BtnAlt.Clicked() {
+		t.confirmedSongAction()
+		t.ConfirmSongDialog.Visible = false
+	}
+	for t.ConfirmSongDialog.BtnCancel.Clicked() {
+		t.ConfirmSongDialog.Visible = false
+	}
+}
+
+func (t *Tracker) confirmedSongAction() {
+	switch t.ConfirmSongActionType {
+	case ConfirmLoad:
+		t.loadSong()
+	case ConfirmNew:
+		t.ResetSong()
+		t.SetFilePath("")
+		t.window.Option(app.Title("Sointu Tracker"))
+		t.ClearUndoHistory()
+		t.SetChangedSinceSave(false)
+	case ConfirmQuit:
+		t.quitted = true
+	}
+}
+
+func (t *Tracker) TryResetSong() {
+	if t.ChangedSinceSave() {
+		t.ConfirmSongActionType = ConfirmNew
+		t.ConfirmSongDialog.Visible = true
+		return
+	}
+	t.ResetSong()
+	t.SetFilePath("")
+	t.window.Option(app.Title("Sointu Tracker"))
+	t.ClearUndoHistory()
+	t.SetChangedSinceSave(false)
+}
+
+func (t *Tracker) TryQuit() bool {
+	if t.ChangedSinceSave() {
+		t.ConfirmSongActionType = ConfirmQuit
+		t.ConfirmSongDialog.Visible = true
+		return false
+	}
+	t.quitted = true
+	return true
 }
 
 func (t *Tracker) layoutBottom(gtx layout.Context) layout.Dimensions {