Hi Tav,

thanks for looking into this!

One question to get on the same page:
This is about sliders like "Blur" and "Opacity" (which are re-used in some other places, too), right? However the actual color sliders in the Fill and Stroke dialog are not affected?

Some thoughts from my side:

• The "top part" dragging is very useful, we should have that.
  The "bottom part" dragging never felt quite right for me and was actually very confusing when I first started using Inkscape, so personally I'd be fine with dropping that.

• Having text and the spinner inside the widget is nice as it saves a lot of space and creates a clean UI control that is immediately recognizable as such (in contrast to multiple controls loosely packed into a box with each other).
  If it's implementable with reasonable effort it's probably good to keep it, especially for locations where there is not much room for an additional label and spinner (e.g. in the toolbar of the various tools that use the widget).

• The previous bullet point is only true if it's done right - thanks to gtk3's wasteful use of screen space I'd consider most spinners in the toolbar broken right now (the label is usually hidden behind an ellipsis; due to the two huge buttons which are now placed side-by-side the usable width decreases even more, so we either need a more economic solution or need to rethink the use of spin sliders in the toolbar fundamentally.
  

• One performance consideration that might be worth to have in mind when doing the rewrite:
  For some reason the custom spinner widget has a much worse redraw performance than other spinner implementations (e.g. the ones in the color selector):
  If I change opacity of an object the widget only updates a few times per second and is redrawn with a delay (canvas reflects the current value properly though). In contrast if I change the fill opacity of the same object this spinner widget redraws without noticeable delay.
  (strike that part - it only seems to affect the gtk2 build and I assume you won't backport this to 0.92.x)

TLDR: I kind of like the spin sliders like they are now for "Blur"/"Opacity" (and could do without the bottom part sliding), however they waste too much space to be useful in toolbars right now.

Best Regards,
Eduard

Am 04.12.2017 um 13:42 schrieb Tavmjong Bah:

Hi,

I've been looking into replacing the Gimp Spin Slider widget (e.g
Blur/Opacity in the Fill and Stroke dialog). The widget is licensed
under GPLv3 and is the only reason Inkscape as a whole is licensed
under GPLv3 rather GPLv2.. The board sometime ago agree that being a
GPLv2 program was desirable (I don't remember the exact reasoning).

A normal Gtk Spin Slider (aka Gtk::SpinButton) has an option to show
the "progress" of slider, that is the percentage (defined in some
arbitrary way) between a minimum and maximum value. This in Gtk 2 is
shown as a solid blue bar with width proportional to the value that
covers the widget from top to bottom. In Gtk 3 the solid blue bar is
replaced by a thin blue bar at the bottom of the widget.

As far as I can tell, the Gimp version of the slider makes three
changes:

1. It allows for a label inside the widget. This is a nice space saving
feature. The widget handles changing the label text from black to white
as the progress bar moves across the label.

2. It allows for a non-uniform scale by adding a "gamma" factor.

3. It adds the ability to drag the progress bar to change the value. If
one drags from the top (down arrow cursor) the change follows the
cursor directly. If one drags along the bottom half (double headed
cursor) the change is finer and relative to the current value.

I've always found that dragging the progress bar to be a bit awkward.
One problem is that one can not start the drag at the far right of the
widget as that area is reserved for typing a value directly in. Also,
the different functionality of starting the drag in the top of the
widget vs. the bottom of the widget is confusing.

Since I am rewriting this widget, I can adjust it to what people want:

* Do you want the progress bar?

* If so, should it be the full height of the widget (quite a bit more
complicated)?

* Do you want to be able to drag the bar? With one/two methods?

* Any other changes?

Thanks,

Tav








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