Detect if a certain key is pressed during a mouse click

[monocasual laboratories]

Hi,

In my handle() method I'm trying to detect if a certain key (FL_Shift_L specifically) is being pressed during a mouse click. I'm aware of the existence of Fl::event_shift(), but it's too generic - I need to detect just the left shift. Also, the key might change in the future from FL_Shift_L to something else (say FL_Page_Down) so I'm looking for a more flexible approach. Any help?

Thanks in advance

[pvrose]

On 15 February 2022, at 21:30, monocasual laboratories <monoc...@gmail.com> wrote:

>Hi,
>
>In my handle() method I'm trying to detect if a certain key (FL_Shift_L specifically) is being pressed during a mouse click. I'm aware of the existence of Fl::event_shift(), but it's too generic - I need to detect just the left shift. Also, the key might change in the future from FL_Shift_L to something else (say FL_Page_Down) so I'm looking for a more flexible approach. Any help?

Hi "Monocausal",

You can detect key-up and key-down events on individual keys, including shift-L. Use this to check if your designated key is down on the mouse event.

Regards Phil.
>
>Thanks in advance
>
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[Ian MacArthur]

It might also depend on what host you are on - particularly X11 can be a bit odd about delivering  events for modifier keys without an associated "main" key, so getting a "bare" Shift key from the X11 events may be unreliable (though IIRC that depends somewhat on X11 system and WM in use and etc...) 

You can get at the raw HID events or etc. on Linux, but that's a nightmare to work with in an app, so I'd not be keen on going that way...

If you look at the test/keyboard demo, you can see how it tracks the various key presses and perhaps extend from that sort of idea?

[monocasual laboratories]

Thank you all for the suggestions. I'll look into the keyboard demo and see what I can get from it. 

Giovanni

[Matthias Melcher]

You can check the status of any key using Fl::get_key(): https://www.fltk.org/doc-1.4/group__fl__events.html#gab7049319eed772c8a22cf2c0eb484a39 . Fl::event_state)( returns among other things a mask of modifier keys and mouse buttons that are currently pressed, https://www.fltk.org/doc-1.4/group__fl__events.html#gafa17a5b4d8d9163631c88142e60447ed, however, it does not differentiate between left and right shift key. Some of our supported platforms do not differentiate between left and right modifiers anyway.