Re: [PATCH] gdb/python: new selected_context event

[Eli Zaretskii <eliz@gnu.org>]

> From: Andrew Burgess <aburgess@redhat.com>
> Cc: Andrew Burgess <aburgess@redhat.com>
> Date: Sun, 22 Feb 2026 16:02:58 +0000
> 
> This commit introduces a new Python event, selected_context.  This
> event is attached to the user_selected_context_changed observer, which
> triggers when the user changes the currently selected inferior,
> thread, or frame.
> 
> Adding this event allows a Python extension to update in response to
> user driven changes without having to poll the state from a
> before_prompt hook, which is what I currently do to achieve the same
> results.
> 
> I did consider splitting the user_selected_context_changed observer
> into 3 separate Python events, inferior_changed, thread_changed, and
> frame_changed, but I couldn't see any significant advantage to doing
> this, so in the end I went with just a single event, and the event
> object contains the inferior, thread, and frame.
> 
> Additionally, the user isn't informed about which aspect of the
> context changed.  That is, every event carries the inferior, thread,
> and frame, so an event triggered when switching frames will looks
> identical to an event triggered when switching inferiors.  If the user
> wants to know what changed then they will have to track the current
> state themselves, and then compare the event state to the stored
> current state.  In many cases though I suspect that just being told
> something changed, and then updating everything will be sufficient,
> which is why I've not bothered trying to inform the user what changed.
> ---
>  gdb/NEWS                                      |   7 +
>  gdb/doc/python.texi                           |  35 +++++
>  gdb/python/py-all-events.def                  |   1 +
>  gdb/python/py-event-types.def                 |   5 +
>  gdb/python/py-inferior.c                      |  54 ++++++++
>  .../gdb.python/py-selected-context.c          |  56 ++++++++
>  .../gdb.python/py-selected-context.exp        | 130 ++++++++++++++++++
>  .../gdb.python/py-selected-context.py         |  57 ++++++++
>  8 files changed, 345 insertions(+)
>  create mode 100644 gdb/testsuite/gdb.python/py-selected-context.c
>  create mode 100644 gdb/testsuite/gdb.python/py-selected-context.exp
>  create mode 100644 gdb/testsuite/gdb.python/py-selected-context.py

The documentation parts are okay, thanks.

Reviewed-By: Eli Zaretskii <eliz@gnu.org>