GODT-22: Frontend-backend

- GODT-1246 Implement settings view.
- GODT-1257 GODT-1246: Account and Help view
- GODT-1298: Minimal working build (panics)
- GODT-1298: loading QML (needs Popup window)
- GODT-1298: WARN: Adding PopupWindow not possible!
    In therecipe qt the `quickwidgets` classes are within `quick` module, but
    forgot to add library and include paths into cgo flags. Therefore
    compilation fails and it would be hard to patch therecipe in order to
    fix it.

    I am not sure if rewrite PopupWindow into go would make any difference,
    therefore I decided to use normal QML Window without borders.
- GODT-1298: Rework status window, add backend props, slots and signals.
- GODT-1298: Users
- GODT-1298: Login
- GODT-1298: WIP Help and bug report
- GODT-1178: MacOS dock icon control
- GODT-1298: Help, bug report, update and events
- GODT-1298: Apple Mail config and Settings (without cache on disk)

internal/frontend/qt/frontend_events.go

@@ -0,0 +1,85 @@
+// Copyright (c) 2021 Proton Technologies AG
+//
+// This file is part of ProtonMail Bridge.
+//
+// ProtonMail Bridge is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// ProtonMail Bridge is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with ProtonMail Bridge.  If not, see <https://www.gnu.org/licenses/>.
+
+// +build build_qt
+
+// Package qt provides communication between Qt/QML frontend and Go backend
+package qt
+
+import (
+	"strings"
+
+	"github.com/ProtonMail/proton-bridge/internal/events"
+)
+
+func (f *FrontendQt) watchEvents() {
+	f.WaitUntilFrontendIsReady()
+
+	errorCh := f.eventListener.ProvideChannel(events.ErrorEvent)
+	credentialsErrorCh := f.eventListener.ProvideChannel(events.CredentialsErrorEvent)
+	noActiveKeyForRecipientCh := f.eventListener.ProvideChannel(events.NoActiveKeyForRecipientEvent)
+	internetOffCh := f.eventListener.ProvideChannel(events.InternetOffEvent)
+	internetOnCh := f.eventListener.ProvideChannel(events.InternetOnEvent)
+	secondInstanceCh := f.eventListener.ProvideChannel(events.SecondInstanceEvent)
+	restartBridgeCh := f.eventListener.ProvideChannel(events.RestartBridgeEvent)
+	addressChangedCh := f.eventListener.ProvideChannel(events.AddressChangedEvent)
+	addressChangedLogoutCh := f.eventListener.ProvideChannel(events.AddressChangedLogoutEvent)
+	logoutCh := f.eventListener.ProvideChannel(events.LogoutEvent)
+	updateApplicationCh := f.eventListener.ProvideChannel(events.UpgradeApplicationEvent)
+	userChangedCh := f.eventListener.ProvideChannel(events.UserRefreshEvent)
+	certIssue := f.eventListener.ProvideChannel(events.TLSCertIssue)
+
+	for {
+		select {
+		case errorDetails := <-errorCh:
+			if strings.Contains(errorDetails, "IMAP failed") {
+				f.qml.PortIssueIMAP()
+			}
+			if strings.Contains(errorDetails, "SMTP failed") {
+				f.qml.PortIssueSMTP()
+			}
+		case <-credentialsErrorCh:
+			f.qml.NotifyHasNoKeychain()
+		case email := <-noActiveKeyForRecipientCh:
+			f.qml.NoActiveKeyForRecipient(email)
+		case <-internetOffCh:
+			f.qml.InternetOff()
+		case <-internetOnCh:
+			f.qml.InternetOn()
+		case <-secondInstanceCh:
+			f.qml.ShowMainWindow()
+		case <-restartBridgeCh:
+			f.restart()
+		case address := <-addressChangedCh:
+			f.qml.AddressChanged(address)
+		case address := <-addressChangedLogoutCh:
+			f.qml.AddressChangedLogout(address)
+		case userID := <-logoutCh:
+			user, err := f.bridge.GetUser(userID)
+			if err != nil {
+				return
+			}
+			f.qml.UserDisconnected(user.Username())
+		case <-updateApplicationCh:
+			f.updateForce()
+		case userID := <-userChangedCh:
+			f.userChanged(userID)
+		case <-certIssue:
+			f.qml.ApiCertIssue()
+		}
+	}
+}