Make web app display mode configurable

The change is visible after reinstalling the web app. 

It's not compatible with all browsers.

See https://developer.mozilla.org/en-US/docs/Web/Manifest/display

ui/form/settings.go

@@ -26,6 +26,7 @@ type SettingsForm struct {
 	ShowReadingTime   bool
 	CustomCSS         string
 	EntrySwipe        bool
+	DisplayMode       string
 }
 
 // Merge updates the fields of the given user.
@@ -40,6 +41,7 @@ func (s *SettingsForm) Merge(user *model.User) *model.User {
 	user.ShowReadingTime = s.ShowReadingTime
 	user.Stylesheet = s.CustomCSS
 	user.EntrySwipe = s.EntrySwipe
+	user.DisplayMode = s.DisplayMode
 
 	if s.Password != "" {
 		user.Password = s.Password
@@ -50,7 +52,7 @@ func (s *SettingsForm) Merge(user *model.User) *model.User {
 
 // Validate makes sure the form values are valid.
 func (s *SettingsForm) Validate() error {
-	if s.Username == "" || s.Theme == "" || s.Language == "" || s.Timezone == "" || s.EntryDirection == "" {
+	if s.Username == "" || s.Theme == "" || s.Language == "" || s.Timezone == "" || s.EntryDirection == "" || s.DisplayMode == "" {
 		return errors.NewLocalizedError("error.settings_mandatory_fields")
 	}
 
@@ -87,5 +89,6 @@ func NewSettingsForm(r *http.Request) *SettingsForm {
 		ShowReadingTime:   r.FormValue("show_reading_time") == "1",
 		CustomCSS:         r.FormValue("custom_css"),
 		EntrySwipe:        r.FormValue("entry_swipe") == "1",
+		DisplayMode:       r.FormValue("display_mode"),
 	}
 }

ui/form/settings_test.go

@@ -14,6 +14,7 @@ func TestValid(t *testing.T) {
 		Timezone:       "UTC",
 		EntryDirection: "asc",
 		EntriesPerPage: 50,
+		DisplayMode:    "standalone",
 	}
 
 	err := settings.Validate()
@@ -32,6 +33,7 @@ func TestConfirmationEmpty(t *testing.T) {
 		Timezone:       "UTC",
 		EntryDirection: "asc",
 		EntriesPerPage: 50,
+		DisplayMode:    "standalone",
 	}
 
 	err := settings.Validate()
@@ -54,6 +56,7 @@ func TestConfirmationIncorrect(t *testing.T) {
 		Timezone:       "UTC",
 		EntryDirection: "asc",
 		EntriesPerPage: 50,
+		DisplayMode:    "standalone",
 	}
 
 	err := settings.Validate()

ui/settings_show.go

@@ -37,6 +37,7 @@ func (h *handler) showSettingsPage(w http.ResponseWriter, r *http.Request) {
 		ShowReadingTime:   user.ShowReadingTime,
 		CustomCSS:         user.Stylesheet,
 		EntrySwipe:        user.EntrySwipe,
+		DisplayMode:       user.DisplayMode,
 	}
 
 	timezones, err := h.store.Timezones()

ui/settings_update.go

@@ -60,6 +60,7 @@ func (h *handler) updateSettings(w http.ResponseWriter, r *http.Request) {
 		Timezone:       model.OptionalString(settingsForm.Timezone),
 		EntryDirection: model.OptionalString(settingsForm.EntryDirection),
 		EntriesPerPage: model.OptionalInt(settingsForm.EntriesPerPage),
+		DisplayMode:    model.OptionalString(settingsForm.DisplayMode),
 	}
 
 	if validationErr := validator.ValidateUserModification(h.store, loggedUser.ID, userModificationRequest); validationErr != nil {

ui/static_manifest.go

@@ -44,12 +44,21 @@ func (h *handler) showWebManifest(w http.ResponseWriter, r *http.Request) {
 		BackgroundColor string                 `json:"background_color"`
 	}
 
+	displayMode := "standalone"
+	if request.IsAuthenticated(r) {
+		user, err := h.store.UserByID(request.UserID(r))
+		if err != nil {
+			json.ServerError(w, r, err)
+			return
+		}
+		displayMode = user.DisplayMode
+	}
 	themeColor := model.ThemeColor(request.UserTheme(r))
 	manifest := &webManifest{
 		Name:            "Miniflux",
 		ShortName:       "Miniflux",
 		Description:     "Minimalist Feed Reader",
-		Display:         "standalone",
+		Display:         displayMode,
 		StartURL:        route.Path(h.router, "unread"),
 		ThemeColor:      themeColor,
 		BackgroundColor: themeColor,