Touch Screen Control of Fl_Slider Position

[Dave Branson]

I am trying to use a Fl_Hor_Value_Slider on a 3.5" touch screen as input to control the speed of a fan with a Raspberry Pi 4 B running Linux.  I am having success with a mouse to control the position of the slider knob, but ultimately mouse input will not be an option for the finalized use, as the Pi & touch screen will be mounted on the fan unit housing.

Any advise will be appreciated.

[Ian MacArthur]

On 21 Oct 2020, at 04:39, Dave Branson wrote:
>
> I am trying to use a Fl_Hor_Value_Slider on a 3.5" touch screen as input to control the speed of a fan with a Raspberry Pi 4 B running Linux. I am having success with a mouse to control the position of the slider knob, but ultimately mouse input will not be an option for the finalized use, as the Pi & touch screen will be mounted on the fan unit housing.

Are you seeing some problem when doing this, and if so, what?

I don’t have access to a touchscreen on a Pi, but my XPS-13 running Ubuntu has a touchscreen, and when I tried that the widgets (including the sliders) seemed to be responding just fine to my screen touches...

Is the screen on your Pi not responding correctly? What is happening?

Can you add a debug print to the widget handle, so we can see what events are being delivered to the widget?

FWIW, when I have used small touch screens in the past, I’ve found the calibration / alignment of the touch with the image seems to be very poor in a lot of cases, so it is probably worth checking that is well calibrated in case that is throwing the whole business off.