Introduce GcalEventPopover

GcalEventPopover gives a preview of the event, and handy access
to the event description and information. It also allows easily
joining meetings if any one if available.

The list of supported meeting URLs is small now, but I hope
more people will contribute as we go.

It is also possible to edit the event through an edit button.

src/gui/gcal-event-widget.c

@@ -25,6 +25,8 @@
 #include "gcal-application.h"
 #include "gcal-context.h"
 #include "gcal-clock.h"
+#include "gcal-debug.h"
+#include "gcal-event-popover.h"
 #include "gcal-event-widget.h"
 #include "gcal-utils.h"
 
@@ -32,6 +34,13 @@
 #define INTENSITY(c)  ((c->red) * 0.30 + (c->green) * 0.59 + (c->blue) * 0.11)
 #define ICON_SIZE     16
 
+typedef struct
+{
+  GcalEventWidget *event_widget;
+  GcalEventPreviewCallback callback;
+  gpointer user_data;
+} PreviewData;
+
 struct _GcalEventWidget
 {
   GtkBin              parent;
@@ -527,6 +536,40 @@ gcal_event_widget_set_event_internal (GcalEventWidget *self,
                           G_BINDING_DEFAULT | G_BINDING_SYNC_CREATE);
 }
 
+static void
+reply_preview_callback (GtkWidget              *event_popover,
+                        PreviewData            *data,
+                        GcalEventPreviewAction  action)
+{
+  if (data->callback)
+    data->callback (data->event_widget, action, data->user_data);
+
+  g_signal_handlers_disconnect_by_data (event_popover, data);
+
+  gtk_widget_destroy (event_popover);
+
+  g_clear_pointer (&data, g_free);
+}
+
+
+/*
+ * Callbacks
+ */
+
+static void
+on_event_popover_closed_cb (GtkWidget   *event_popover,
+                            PreviewData *data)
+{
+  reply_preview_callback (event_popover, data, GCAL_EVENT_PREVIEW_ACTION_NONE);
+}
+
+static void
+on_event_popover_edit_cb (GtkWidget   *event_popover,
+                               PreviewData *data)
+{
+  reply_preview_callback (event_popover, data, GCAL_EVENT_PREVIEW_ACTION_EDIT);
+}
+
 
 /*
  * GtkWidget overrides
@@ -1134,6 +1177,40 @@ gcal_event_widget_set_date_start (GcalEventWidget *self,
     }
 }
 
+/**
+ * gcal_event_widget_show_preview:
+ * @self: a #GcalEventWidget
+ * @callback: (nullable): callback for the event preview
+ * @user_data: (nullable): user data for @callback
+ *
+ * Shows an event preview popover for this event widget, and
+ * calls @callback when the popover is either dismissed, or
+ * the edit button is clicked.
+ */
+void
+gcal_event_widget_show_preview (GcalEventWidget          *self,
+                                GcalEventPreviewCallback  callback,
+                                gpointer                  user_data)
+{
+  PreviewData *data;
+  GtkWidget *event_popover;
+
+  GCAL_ENTRY;
+
+  data = g_new0 (PreviewData, 1);
+  data->event_widget = self;
+  data->callback = callback;
+  data->user_data = user_data;
+
+  event_popover = gcal_event_popover_new (self->context, self->event);
+  gtk_popover_set_relative_to (GTK_POPOVER (event_popover), GTK_WIDGET (self));
+  g_signal_connect (event_popover, "closed", G_CALLBACK (on_event_popover_closed_cb), data);
+  g_signal_connect (event_popover, "edit", G_CALLBACK (on_event_popover_edit_cb), data);
+  gtk_popover_popup (GTK_POPOVER (event_popover));
+
+  GCAL_EXIT;
+}
+
 /**
  * gcal_event_widget_get_event:
  * @self: a #GcalEventWidget