Qt properties editor discards color alpha

[anntzer]

plot([0, 1], [0, 1], color=(0, 0, 0, .5)) (a gray line) then click on the qt editor. Upon clicking on OK, the line becomes black, likely because the alpha value has been discarded.
Tested on 1.5.1 and master.

[TuanNguyen27]

I would like to work on this issue, how do i start ?

[tacaswell]

@TuanNguyen27 You just did 😉

[TuanNguyen27]

@tacaswell thanks for the reply! my apologies for the vague question, I'm new, as you can tell, so I'm wondering where should I look in the code base to get started?

[tacaswell]

The color handling in https://github.com/matplotlib/matplotlib/blob/master/lib/matplotlib/backends/qt_editor/figureoptions.py

I may be reconsidering tagging this as easy, there maybe a non-trivial amount of Qt work involved.

[anntzer]

Actually, the Qt side of things is relatively easy, because QColorDialog (Qt 4.8 and 5.6) provide the ShowAlphaChannel option (http://doc.qt.io/qt-5.6/qcolordialog.html#ColorDialogOption-enum). The more tricky part is that functions in matplotlib.colors in charge of the #rrggbb to color conversion (in both directions: rgb2hex, ColorConverter.to_rgba, is_color_like) do not handle the #rrggbbaa format, so quite a bit of work would be needed on that side.

[WeatherGod]

IIRC, there is actually an open feature request to support #rrggbbaa
format. So, getting that to work would actually close two issues at once.

On Wed, May 4, 2016 at 10:11 PM, Antony Lee notifications@github.com
wrote:

Actually, the Qt side of things is relatively easy, because QColorDialog
(Qt 4.8 and 5.6) provide the ShowAlphaChannel option (
http://doc.qt.io/qt-5.6/qcolordialog.html#ColorDialogOption-enum). The
more tricky part is that functions in matplotlib.colors in charge of the
#rrggbb to color conversion (in both directions: rgb2hex,
ColorConverter.to_rgba, is_color_like) do not handle the #rrggbbaa
format, so quite a bit of work would be needed on that side.

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