Picker flashes on elementary 0.4 (ubuntu 16.04)

[sgpthomas]

I think you already know about this bug but I thought that I should report it anyways.

In the color pick mode, the magnifying lens flashes when you move it.

[stuartlangridge]

I do know about it. I do not know how to fix it. I would be eager to hear from any X or GTK or graphics driver hackers who can give me some sense of why it happens.

[Joecorleone]

I just installed it on Lubuntu 14.04 and I can report the same flashy behaviour. Picker version 1.4.
Nonetheless, thanks for the nice tool. (Great that it got featured on OMGubuntu)

[HEXcube]

Can confirm the lens flashes and flickers on my home notebook running Ubuntu 14.04LTS with Unity 7. Tested on the latest pick-colour-picker v1.5 from PPA. But surprisingly, the issue doesn't exist on my Ubuntu GNOME 16.04LTS workstation. 😮

I think this is a graphics driver issue. 😕 Coz, I'm using proprietary AMD graphics driver on Ubuntu 14.04LTS home notebook, whereas my work machine runs open source Intel drivers bundled with 16.04 kernel.

[moqmar]

Works on my desktop with NVIDIA graphics, doesn't work on my notebook with Intel Graphics. So, if @HEXcube has a workstation with Intel Graphics where everything works fine (also with the bundled open source drivers), I guess it's a bit more complicated as it isn't even manufacturer-related... :/

[stuartlangridge]

I can confirm that I had the flickering problem on Ubuntu 14.04 with Intel graphics and it was fixed when I updated to Ubuntu 16.04.

[moqmar]

Alright, I found where the problem is coming from:

• The maximum snapsize seems to be 128x128. https://developer.gnome.org/gdk3/stable/GdkDisplay.html#gdk-display-get-maximal-cursor-size confirms this, although I'm confused by the fact that we have a 120+200 = 320x320 cursor - testing confirms that everything is still dependent just on the snapsize.
• Now, on my notebook, GNOME is scaled by 2 because I have a screen with high DPI. This also scales up the cursor, making the effective snapsize of the picker 240x240 (instead of 120x120). In fact, the maximum snapsize on my Laptop (nothing flickers at all) is 64x64 - exactly half the original one.
• get_maximal_cursor_size() is the same on my PC and on my laptop. get_default_cursor_size() isn't though, so I used the cursor size from org.gnome.desktop.interface.cursor-size and compare it to that value to get the scale.
• I don't know if that dconf value is set everywhere (e.g. LXDE) (edit: or if this issue exists on (maybe non-HiDPI) systems where those values match, e.g. because the maximum cursor size differs), so I added the CURSOR_SCALE environment variable which should contain a float value of how much the cursor is scaled up by the system (e.g. CURSOR_SCALE=1.5 yields a snapsize of 120/1.5 = 80). If this exists, it overrides the calculated size.

[stuartlangridge]

I'd be happy to hear testing results for this from people. (I can't test it myself; as noted, my cursor already doesn't flash on 16.04.)

[o-alquimista]

This is reproducible here.

I do not have HiDPI, and I'm running Ubuntu 18.04.2 (GNOME on Xorg).
Graphics device: AMD RX 560 (open source AMDGPU stack, default setup)

[moqmar]

So, I have updated this to the latest master and can confirm that it still works for me on a new linux installation. Would be great to see the PR getting merged. Or are we waiting on #72?

[Mobuos]

I have the same issue here, the picker flashes while moving it.