[gnome-calendar/mcatanzaro/add-calendar: 2/3] new-calendar-page: properly track state of URL entry and Add button

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 172c59819fe8e833a6700221ea950caa813c1b86
Author: Michael Catanzaro <mcatanzaro gnome org>
Date:   Wed Apr 1 21:26:33 2020 -0500

    new-calendar-page: properly track state of URL entry and Add button
    
    Currently, when the user enters an invalid URL -- a URL that does not
    pass SoupURI's URI format validation -- then we set the error style
    class on the URL entry to turn the border of the entry red. For example,
    if I try to enter "dog" then GNOME Calendar catches this and flags the
    entry as red.
    
    But there are some problems.
    
    First of all, GNOME Calendar doesn't do anything to prevent users from
    entering URLs that are syntatically valid but not usable as calendars.
    The code knows whether the URL was successfully parsed as a calendar
    file, it just doesn't do anything with this information. So there is no
    red warning if I try to use https://example.com as a calendar, even
    though the dialog knows that it didn't work.
    
    Secondly, GNOME Calendar allows pressing the Add button even if the URL
    entry contains invalid input, but only if the Calendar Name has been
    entered. The dialog thinks: "if I have a name, but not a valid URL, then
    the user wants to create a new, empty local calendar!" But this is not
    right. If the user has typed anything in the URL entry, then the goal is
    to import a new calendar, not to create a new one.
    
    This commit changes set_url_entry_error() into update_url_entry_state(),
    and gives it responsibility for updating the add button sensitivity and
    URL entry pulsing in addition to the URL entry style class, solving both
    of the above problems.
    
    As a side effect, this also closes a race window where the Add button
    remains sensitive for half a second after typing new text in the URL entry.
    At this point, we don't yet know whether the URL is valid, because we
    wait half a second before validating the URL, so we shouldn't allow the
    user to activate the Add button during this race window.
    
    Fixes #481

 .../calendar-management/gcal-new-calendar-page.c   | 56 ++++++++++++++--------
 1 file changed, 35 insertions(+), 21 deletions(-)
---
diff --git a/src/gui/calendar-management/gcal-new-calendar-page.c 
b/src/gui/calendar-management/gcal-new-calendar-page.c
index e5e526c1..ee784fff 100644
--- a/src/gui/calendar-management/gcal-new-calendar-page.c
+++ b/src/gui/calendar-management/gcal-new-calendar-page.c
@@ -31,12 +31,21 @@
 
 #define ENTRY_PROGRESS_TIMEOUT 100 // ms
 
+typedef enum
+{
+  ENTRY_STATE_EMPTY,
+  ENTRY_STATE_VALIDATING,
+  ENTRY_STATE_VALID,
+  ENTRY_STATE_INVALID
+} EntryState;
+
 struct _GcalNewCalendarPage
 {
   GtkBox              parent;
 
   GtkWidget          *add_button;
   GtkEntry           *calendar_address_entry;
+  EntryState          calendar_address_entry_state;
   GtkFileChooser     *calendar_file_chooser_button;
   GtkFileFilter      *calendar_file_filter;
   GtkWidget          *cancel_button;
@@ -130,7 +139,10 @@ update_add_button (GcalNewCalendarPage *self)
 {
   gboolean valid;
 
-  valid = self->local_source != NULL || self->remote_sources != NULL;
+  valid = (self->local_source != NULL || self->remote_sources != NULL) &&
+      self->calendar_address_entry_state != ENTRY_STATE_VALIDATING &&
+      self->calendar_address_entry_state != ENTRY_STATE_INVALID;
+
   gtk_widget_set_sensitive (self->add_button, valid);
 }
 
@@ -184,17 +196,21 @@ toggle_url_entry_pulsing (GcalNewCalendarPage *self,
 }
 
 static void
-set_url_entry_error (GcalNewCalendarPage *self,
-                     gboolean             error)
+update_url_entry_state (GcalNewCalendarPage *self,
+                        EntryState           state)
 {
   GtkStyleContext *context;
 
-  context = gtk_widget_get_style_context (GTK_WIDGET (self->calendar_address_entry));
+  self->calendar_address_entry_state = state;
 
-  if (error)
+  context = gtk_widget_get_style_context (GTK_WIDGET (self->calendar_address_entry));
+  if (state == ENTRY_STATE_INVALID)
     gtk_style_context_add_class (context, "error");
   else
     gtk_style_context_remove_class (context, "error");
+
+  update_add_button (self);
+  toggle_url_entry_pulsing (self, state == ENTRY_STATE_VALIDATING);
 }
 
 static void
@@ -218,8 +234,7 @@ discover_sources (GcalNewCalendarPage *self)
                                   self->cancellable,
                                   sources_discovered_cb,
                                   self);
-
-  toggle_url_entry_pulsing (self, TRUE);
+  update_url_entry_state (self, ENTRY_STATE_VALIDATING);
 
   GCAL_EXIT;
 }
@@ -314,7 +329,7 @@ sources_discovered_cb (GObject      *source_object,
       else
         {
           g_warning ("Error finding sources: %s", error->message);
-          toggle_url_entry_pulsing (self, FALSE);
+          update_url_entry_state (self, ENTRY_STATE_INVALID);
         }
       GCAL_RETURN ();
     }
@@ -322,9 +337,7 @@ sources_discovered_cb (GObject      *source_object,
   g_debug ("Found %u sources", sources->len);
 
   self->remote_sources = g_steal_pointer (&sources);
-  update_add_button (self);
-
-  toggle_url_entry_pulsing (self, FALSE);
+  update_url_entry_state (self, ENTRY_STATE_VALID);
 
   GCAL_EXIT;
 }
@@ -334,21 +347,22 @@ validate_url_cb (gpointer data)
 {
   GcalNewCalendarPage *self = data;
   g_autoptr (SoupURI) uri = NULL;
-  gboolean valid_uri;
 
   GCAL_ENTRY;
 
   self->validate_url_resource_id = 0;
 
   uri = soup_uri_new (gtk_entry_get_text (self->calendar_address_entry));
-  valid_uri = uri != NULL && SOUP_URI_IS_VALID (uri);
-
-  set_url_entry_error (self, !valid_uri);
 
-  if (valid_uri)
-    discover_sources (self);
+  if (uri != NULL && SOUP_URI_IS_VALID (uri))
+    {
+      discover_sources (self);
+    }
   else
-    g_debug ("Invalid URL passed");
+    {
+      update_url_entry_state (self, ENTRY_STATE_INVALID);
+      g_debug ("Invalid URL passed");
+    }
 
   GCAL_RETURN (G_SOURCE_REMOVE);
 }
@@ -395,7 +409,7 @@ on_credential_button_clicked_cb (GtkWidget           *button,
   if (button == self->credentials_connect_button)
     discover_sources (self);
   else
-    toggle_url_entry_pulsing (self, FALSE);
+    update_url_entry_state (self, ENTRY_STATE_INVALID);
 
   popdown_credentials_popover (self);
 }
@@ -427,7 +441,6 @@ on_url_entry_text_changed_cb (GtkEntry            *entry,
 
   /* Cleanup previous remote sources */
   g_clear_pointer (&self->remote_sources, g_ptr_array_unref);
-  update_add_button (self);
 
   if (self->validate_url_resource_id != 0)
     g_clear_handle_id (&self->validate_url_resource_id, g_source_remove);
@@ -439,11 +452,12 @@ on_url_entry_text_changed_cb (GtkEntry            *entry,
        * it fails.
        */
       self->validate_url_resource_id = g_timeout_add (500, validate_url_cb, self);
+      update_url_entry_state (self, ENTRY_STATE_VALIDATING);
     }
   else
     {
       gtk_entry_set_progress_fraction (self->calendar_address_entry, 0);
-      set_url_entry_error (self, FALSE);
+      update_url_entry_state (self, ENTRY_STATE_EMPTY);
     }
 
   GCAL_EXIT;