Subject: Re: [linux-audio-dev] Virtual Sliders Considered Harmful
From: Karl JH Millar (kmillar_AT_MIT.EDU)
Date: Fri May 26 2000 - 05:11:29 EEST
Eli wrote:
>On-screen knobs and sliders make me ill. They make me toss in my
>sleep and pull out my eyebrow hairs. They are the bastard demon
>children of real knobs and sliders. Shun them. Turning a knob with a
>mouse is like poking it with a long stick.
>
>I can control four sliders independently, or two knobs; the knobs give
>repeatable absolute position. On-screen I can control one slider or
>zero knobs: knobs are uncontrollable on screen. (I can't keep the
>mouse pointer on a circular track around the knob center and listen to
>the sound at the same time.) On a virtual devices the value I need
>will lie in between two pixels; the real ones can be nudged with great
>precision.
This is a large part of why I believe the host should be largely responsible
for constructing a graphical interface. If the plugin does it, and especially
if the plugin does it with pixmaps, then these problems are very real, as the
details of each element will vary from plugin to plugin.
If on the other hand, the host controls the behaviour of widgets, it can
create a set of sliders, dials etc that are all consistently and relatively
easily controlled, with *consistent* mouse control, *consistent* keyboard
bindings and numerical displays as desired. This consistency makes ease of
use at least possible. A well constructed host would even allow the user to
choose the behaviour of various widgets to whatever he/she finds easiest.
The last thing we want is dials which can be controlled by moving the mouse
up/down, left/right and clockwise/counterclockwise all is use at once.
The analogy with physical hardware, which is all slightly different, fails at
this point. No matter which brand of physical hardware I use, I can control it
in the same way. This is not true when I'm trying to control pictures of
hardware using a mouse or keyboard.
Now the way the host creates the widgets could be a number of ways - hints
as in the current LADSPA API, an XML description, or a LADSPA specific API
which defines all the used objects. Any of these would allow the host to
create a reasonable setup.
Karl.
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