333362 - Figure out what a zero length event means, and check if all code does the right thing

Status: RESOLVED WORKSFORME

(Calendar :: Internal Components, defect)

Description

[Michiel van Leeuwen (email: mvl+moz@)]

It's not clear what an event where the start-time is the same as the end-time means. An event that takes no time is no event...

At least the unifinder might be broken when encountering an all-day event, since bug 306157 was checked in. We also need to check other code to do the right thing (providers, views, printing, etc)

Comment 1

[Joey Minta]

*** Bug 331928 has been marked as a duplicate of this bug. ***

Comment 2

[Andrew N Dowden]

The iCal spec. supports 2 types of non-blocking (transparent) reminder events.

all from rfc2445, 4.6.1 Event Component

(a)  Daily Reminder / Anniversary  (1 or more days, transparent)
     .. to specify an
   anniversary or daily reminder within a calendar. These events have a
   DATE value type for the "DTSTART" property instead of the default
   data type of DATE-TIME. If such a "VEVENT" has a "DTEND" property, it
   MUST be specified as a DATE value also. The anniversary type of
   "VEVENT" can span more than one date (i.e, "DTEND" property value is
   set to a calendar date after the "DTSTART" property value).

     .. For
   cases where a "VEVENT" calendar component specifies a "DTSTART"
   property with a DATE data type but no "DTEND" property, the events
   non-inclusive end is the end of the calendar date specified by the
   "DTSTART" property. 

(b.)  Daily Reminder / Anniversary  (no length, transparent)
   .. For cases where a "VEVENT" calendar component
   specifies a "DTSTART" property with a DATE-TIME data type but no
   "DTEND" property, the event ends on the same calendar date and time
   of day specified by the "DTSTART" property.

Support for type 'a' uses the "all-day" tag, with time shown as '12:00am to 12:00am (non-inclusive)', or 00:00 to 00:00/24:00 (non-inclusive)'.

There are related bugfix / discussions on presentation for these date / times:
	259871  Support for the virtual time 24:00 (0:00 on next day)
	333717  Timezone information lost, causing wrong results from ..
		- for example in New Zealand, shows '12:00pm to 12:00pm'

I ran into UI issues, and auto-correction to end-date when I previously attempted to test for type 'b'.  Is this bug to focus on just type 'b', OR both types?

Comment 3

[Michiel van Leeuwen (email: mvl+moz@)]

Andrew: This bug is not about a, and also not about b. Events without DTEND is not what this bug is about. This bug is about event where DTSTART is equal to DTEND, and both are date-time.

Comment 4

[Andrew N Dowden]

Type 'b' events are reminders that:
 - have a date AND time;  AND
 - have no duration (and are therefore transparent)

I think therefore, that an event with DTSTART (date-time) equal to DTEND should be treated the same way.

That would mean that events loaded (from iCal file) with:
 (a) DTSTART date-time, and no DTEND;  OR
 (b) DTSTART date-time, and DTEND equal to DSTART
should be treated the same.

For the UI (Edit Event) this could either be shown as DTSTART equal to DTEND, or (preferred) with a new tick for 'Reminder' (or radio button (1 of): Duration (default), Reminder, All Day)

Comment 5

[Philipp Preißer-Kewisch [:Fallen][☁️📆]]

I think most code can handle this type of event. If there is a specific issue, lets open a new bug (which will likely happen anyway)