[Interest] Sequence of events in a double click

[John Weeks]

There is a flag that alerts you to the fact that the second 
MousePressEvent is the second of a double-click. Here is our code to 
handle it:
     if (event->flags() & Qt::MouseEventCreatedDoubleClick) {
         return;
     }


And, yes, that was a change between Qt 4 and Qt 5 that caused us quite a 
bit of grief.

-John Weeks
WaveMetrics, a division of Sutter Instrument, Inc.

On 9/3/2025 6:14 AM, Axel Spoerl via Interest wrote:
> Servus Robert,
>
> Just to clarify: Indeed, the behavior is intended.
>
> I am already old ��
>
> :wq
> Axel
>
> Confidential
> ------------------------------------------------------------------------
> *From:* Interest <interest-bounces at qt-project.org> on behalf of 
> Schimkowitsch Robert <Robert.Schimkowitsch at andritz.com>
> *Sent:* Wednesday, 3 September 2025 14:26
> *To:* interest at qt-project.org <interest at qt-project.org>
> *Subject:* Re: [Interest] Sequence of events in a double click
>
> Hi Axel,
>
> thanks for that pointer. I can now follow how 
> QGuiApplicationPrivate::processMouseEvent() first receives the events, 
> detects that an event is a double click, then calls my filter with the 
> original event, and then calls my filter again with an extra double 
> click event in case of a double click. So I guess this is intended 
> behavior.
>
> That said, I use Qt since 2009, so either things have changed 
> sometimes between then and 2017, or the behavior was subtly different 
> when only observing events on the widget or graphics view level. With 
> an event filter, I am of course much lower-level.
>
> I’m getting old...
>
> Kind regards
>
> Robert
>
> *From:*Interest <interest-bounces at qt-project.org> *On Behalf Of *Axel 
> Spoerl via Interest
> *Sent:* Wednesday, 3 September 2025 13:42
> *To:* interest at qt-project.org
> *Subject:* Re: [Interest] Sequence of events in a double click
>
> *CAUTION**: External email.**Do not click on links or open attachments 
> unless you know the sender and that the content is safe.*
>
> Servus Robert,
>
> QGuiApplication::processMouseEvent() consumes the second mouse press 
> event and sends an additional QEvent::Type::MouseButtonDblClick if the 
> time between two presses is within the double click interval 
> (QGuiApplication::styleHints()->mouseDoubleClickInterval()).
>
> That said, when the second press event is received, Qt doesn't know if 
> it meets the criteria for a double click.
> The second press event has been sent for as long as I remember. That 
> is, according to git blame, at least since 2017 ;-)
>
> Cheers
> Axel
>
> Confidential
>
> ------------------------------------------------------------------------
>
> *From:*Interest <interest-bounces at qt-project.org> on behalf of 
> Schimkowitsch Robert <Robert.Schimkowitsch at andritz.com>
> *Sent:* Wednesday, 3 September 2025 11:43
> *To:* interest at qt-project.org <interest at qt-project.org>
> *Subject:* Re: [Interest] Sequence of events in a double click
>
> A small correction: “ButtonDoubleRelease” does not exist. It should 
> read “ButtonRelease”
>
> *From:*Interest <interest-bounces at qt-project.org> *On Behalf Of 
> *Schimkowitsch Robert
> *Sent:* Wednesday, 3 September 2025 11:21
> *To:* interest at qt-project.org
> *Subject:* [Interest] Sequence of events in a double click
>
> *CAUTION**: External email.**Do not click on links or open attachments 
> unless you know the sender and that the content is safe.*
>
> Hi all,
>
> when you perform a double click on a mouse button (=pressing and 
> releasing the mouse button in fast sequence twice), I have, over many 
> years, always expected this sequence:
>
> ButtonPress
>
> ButtonRelease
>
> ButtonDoublePress
>
> ButtonDoubleRelease
>
> It is consistent with what I get when I trace the window events using 
> Spy++ (on Windows, for context) on a simple application (not my own, 
> since Spy++ crashes when encountering the hooks of a serious Qt 
> application, and I currently don’t have a good replacement tool).
>
> However, in my Qt 6.8.2 application using a window event filter, I 
> receive the following sequence:
>
> ButtonPress
>
> ButtonRelease
>
> ButtonPress
>
> ButtonDoublePress
>
> ButtonDoubleRelease
>
> The extra press confuses me. Is this as it should be?
>
> Kind regards
>
> Robert
>
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