Big mouse pointer at login with 4K display but at 1920x1080 screen configuration

[Sancho]

On a laptop with a 4K display but at 1920x1080 resolution setting:

When login in a new session, the mouse cursor has a huge size.
To fix the problem, at every new session login :
+ Open "Mouse and trackpad settings"
+ Switch to mouse "Theme" tab
+ Choose another theme and get back 'default' theme
= the mouse pointer has now a normal size

Remarks:
+ On login screen, the screen resolution is 4K (3840x2160)
+ My session is configured to be 1920x1080
+ This bug occurs either with nouveau or nvidia driver

Additional information:
$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 15.10
Release: 15.10
Codename: wily

$ xfce4-mouse-settings --version
xfce4-mouse-settings 4.12.0 (Xfce 4.12)

$ lspci | grep -ie vga -ie 3d
00:02.0 VGA compatible controller: Intel Corporation Device 191b (rev 06)
02:00.0 3D controller: NVIDIA Corporation GM107M [GeForce GTX 960M] (rev a2)

$ dpkg -l | grep nvidia
ii nvidia-358 358.16-0ubuntu0~gpu15.10.2 amd64 NVIDIA binary driver - version 358.16
ii nvidia-opencl-icd-358 358.16-0ubuntu0~gpu15.10.2 amd64 NVIDIA OpenCL ICD
ii nvidia-prime 0.8.1 amd64 Tools to enable NVIDIA's Prime
ii nvidia-settings 361.28-0ubuntu0~gpu15.10.1 amd64 Tool for configuring the NVIDIA graphics driver

$ prime-select query
nvidia

$ uname -a
Linux sancho-Inspiron-7559 4.2.0-30-generic #36-Ubuntu SMP Fri Feb 26 00:58:07 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

+xpdyinfo attachment

[Sancho (christophe-andral)]

Laptop model : Dell Inspiron 15 7000 series (7537)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.