[linux-audio-dev] Knobs / widget design

[torbenh at gmx.de]

On Wed, Jun 09, 2004 at 04:25:15PM -0700, Tim Hockin wrote:
> On Wed, Jun 09, 2004 at 11:56:59PM +0200, Arnold Krille wrote:
> > Still the question is: What toolkit to use for a 
> > standard-LAD-Gui-elements-set? Or just define the graphics and the handling 
> > and then let everyone implement it in his/her preferred toolkit? The last 
> > would be my suggestion, and maybe I am volunteering to create on for Qt...
> 
> Other way around?  Define a graphics system so I can add my own
> knob-graphics, and you make them work.
> 

ok... small history of my experience with knobs:

i used a gif animation for the galan knob.
seemed nice because i know the size and the number of frames.
dawback: only 1 transparancy bit.

knob looks ugly on black background.

now i moved the code to use png which has real alpha information.
put all frames in a row.

but i have to hardcode the size or the number of frames.
(dont remember what i hardcoded (perhaps both :( ) )

solution is a textfile describing the knob or one integer in the png.
Although it seems nicer to put this metadata into the png, i think i
prefer the textfile, because i want to read the png using gdk-pixbuf and
i dont know how to get the metadata from gdk-pixbuf.

The text file could also define some of the behaviour of the knob in
response to the mouse.

This would allow to make a single widget which can behave like a slider
or a knob. in fact it only displays an animation.

so what do we get ?
---------------------------
nFrames=100
behaviour=0 
image=filename.png
--------------------------

with behaviour being 
0 = knob
1 = slider
2 = 2D Control (??)

the image= could be omitted if we say the name of the textfile should be
filename.ladcontrol or something.

if we agree on something like this i can contribute the gtk2 part of this
very fast.
the gtk1 part needs some work because its still loading gifs

its a widget with a GtkAdjustment... so it can be exchanged on the fly
with a GtkSlider

dont know about the qt side of things but it should be quite easy to do.

please comment...


-- 
torben Hohn
http://galan.sourceforge.net -- The graphical Audio language