Re: [Tuxpaint-devel] Started the port to SDL3

[Pere P. i C. <per...@gm...>]

El dt. 15 de 07 de 2025 a les 14:06 +0100, en/na Bill Kendrick va escriure:
> On Tue, Jul 15, 2025 at 01:53:49AM +0200, Pere Pujal i Carabantes wrote:
> > El dc. 02 de 07 de 2025 a les 10:37 +0200, en/na Pere Pujal i Carabantes va escriure:
> > > I've see them, thanks.
> > > 
> > > Now I am slowly porting the magic tools, one by one.
> > 
> > Magic tools have been ported, I am currently adding PEN pressure support to tuxpaint.c
> > 
> > Pressure draw with the main tip of the pen seems to work, both brush size and brush opacity,
> > can be enabled/disabled with CTRL T for transparency and CTRL W for width.
> > There are some values that may/should? be made available in tuxpaint-config 
> > but for now they are set to what works in my system.
> 
> In this case, by "width" you mean "spacing", correct?

I mean the size of the brush blit on the canvas, 
max pressure results in full size, less pressure results in less size.
Obviously, I had to _also_ scale spacing according to the size,
otherwise the results were incorrect. 

See the picture of 6 first brushes and the sphere drawing 
with and without pressure affecting width and transparency.
https://provant.freeddns.org/pere/public_html/Tux%20Paint/devel/20250716/pressure_tests.png



> There's a feature I'd like to add that allows brush sizes
> to be altered via the UI as well.  I feel as though that
> forthcoming feature would be better served by pressure
> sensitivity, than the spacing feature.  (I admit, I don't
> actually do much art myself, and rarely with a tablet.
> It just 'feels' like pressure changing spacing would be
> confusing.)

If I understand right, this is exactly what I have implemented?
well, just the half of what is implemented, the other half is transparency.


BTW, I am not happy with transparency, one sees the different blits of the brushes in the line,
still investigating...



> For now, until we can add the brush sizing feature
> (or perhaps forever?), I think transparency makes the most
> sense.
> 
> And I would definitely want the ability to disable it for
> users who are not yet familiar/comfortable with pressure
> (i.e., an option to ignore pressure, and always be 100% opaque).

Oh, true, currently it starts always enabled, both for size and for transparency,


> 
> Reporting pressure to Magic Tools probably makes sense, but
> I really need to sit down and think how & when, and how things
> should behave when pressure is unavailable.

That would be also a good addition, I imagine many magic tools could benefit from it.


> 
> Obviously, right now -- for the past 23 years -- pressure has NOT
> been available.  However, once we start adding pressure sensitivity
> to existing tools, and adidng new tools that support it, we'll want
> them all to behave intuitively and sensibly when the input lacks
> pressure (i.e., a regular mouse, a joystick, the keyboard, or a
> tablet with pressure disabled).

Yes, of course, most people don't use tablets/pens to draw.
BTW, are there any touchscreen that is pressure sensitive? (with finger I mean)


> 
> 
> > Still need to decide what to do when the user switches tips to the secondary one, 
> > maybe hardcode it to the eraser tool?
> 
> This is what I've always imagined. :)
> See ancient ticket https://sourceforge.net/p/tuxpaint/feature-requests/8/
> 
> I imagine it could just behave like Tux Paint does when holding
> the [X] key.  From README:
> 
>   Hold the [X] key while clicking for quick access to a small sharp round
>   eraser (not available when the Text or Label tools are selected, when
>   you're in the process of rotating a stamp or shape, or when using an
>   interactive magic tool). Release the mouse to return to your
>   currently-selected tool.
> 
> Of course, if pressure is enabled, then we'd want the eraser
> to behave differently depending on the pressure.
> 
> Right now, Erasers are basically just hard-coded shapes (the old
> "whiteboard eraser" square, then more recently circles, fuzzy
> circles, and transparent circles).  While somewhat limiting in
> many ways, this also means we can just go in and code things how
> we want, for this special stylus version of the [X]-key-held
> eraser.

Will see what I can do :), my first idea was to implement pressure in the Eraser tool, 
fully switch to it when switching pen tip, let the user do its stuff, 
then return to the previous tool when switching the pen again to the main tip.
but as you say in the feature request, what should happen if the user is already in the Eraser tool?

Oh, wait, I see Krita changing to eraser mode when switching from main tip to secondary one, 
but doing nothing if already in eraser mode, it continues in eraser mode and do not changes 
to paint mode when switching again back to the main tip of the pen.

Maybe we can do the same...

> 
> 
> > I use an old Wacom graphire to test, but the pen is very used, I already had to solder it to get it working again.
> > If somebody has a spare graphics tablet that can send my way I will be very grateful :)
> 
> I've asked Pere how I can help here. :-)

Yeah!, Thanks :)

Pere


> 
> -bill!
> 
> 
> _______________________________________________
> Tuxpaint-devel mailing list
> Tux...@li...
> https://lists.sourceforge.net/lists/listinfo/tuxpaint-devel