Am 13.02.2016 um 12:03 schrieb johannes hanika:
short question: is there already an established way to get a bauhaus slider
with a logarithmic scale?
short answer: no. (other than just mapping some mislabeled value to
exp(v) in the gui callback or commit_params..
My idea: we implement a callback functionality into the bauhaus slider:
void dt_bauhaus_slider_set_callback(GtkWidget *w, float
(*value_callback)(float value, int dir))
With 'dir' indicating the direction of the conversion (e.g.
DT_BAUHAUS_SET or DT_BAUHAUS_GET). Advantage: we have quite some
flexibility rather than just logarithmic and normal. By default the
callback is NULL and the bauhaus slider behaves as normal.
For a logarithmic slider the callback could look like:
static float log_slider_callback(float inval, int dir)
{
float outval;
switch(dir)
{
case DT_BAUHAUS_SET:
outval = log10(fmax(inval, 1e-15f));
break;
case DT_BAUHAUS_GET:
outval = exp10(inval);
break;
default:
outval = inval;
}
return outval;
}
I see five locations where the callback must take effect:
1) dt_bauhaus_slider_set() and dt_bauhaus_slider_set_soft()
2) dt_bauhaus_slider_get()
3) on displaying the slider value in the GUI
4) on referencing the current value as "x" in the calculator
5) on setting the new value in the calculator
Ulrich
-jo
Background: I would need a slider for focal length (1mm to 1000mm) and this
would better scale logarithmically.
Ulrich
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