Comment 147 for bug 256142

I believe that i just found a temporary workaround.

Since the flickering seems to be caused by the automatic mode detection on my non-connected VGA output, I used xrandr to force a mode on that output.

I used the following commands

xrandr --newmode dummy 75.00 1280 1301 1333 1408 800 804 808 816 -hsync -vsync
xrandr --addmode VGA dummy
xrandr --output VGA --mode dummy

Those commands cause a lot of flickering but after them, flickering is gone.

The result can be verified with

 $ xrandr --prop | cat -n
     1 Screen 0: minimum 320 x 200, current 1280 x 800, maximum 1280 x 1280
     2 VGA disconnected 1280x800+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
     3 dummy 65.3*
     4 LVDS connected 1280x800+0+0 (normal left inverted right x axis y axis) 261mm x 163mm
     5 EDID_DATA:
     6 00ffffffffffff0006af142100000000
     7 010f0103801a10780a30259855548827
     8 24505400000001010101010101010101
     9 0101010101014c1d0080502010301520
    10 440005a3100000190000000000000000
    11 00000000000000000001000000fe0057
    12 35333832004231323145570a000000fe
    13 00fffdf3e9bb8d6f0001010a2020005f
    14 PANEL_FITTING: full
    15 supported: center full_aspect full
    16 BACKLIGHT_CONTROL: native
    17 supported: native legacy combination kernel
    18 BACKLIGHT: 0 (0x00000000) range: (0,0)
    19 1280x800 65.3*+
    20 1024x768 60.0
    21 800x600 60.3
    22 640x480 59.9
    23 TV disconnected (normal left inverted right x axis y axis)
    24 BOTTOM: 37 (0x00000025) range: (0,100)
    25 RIGHT: 46 (0x0000002e) range: (0,100)
    26 TOP: 36 (0x00000024) range: (0,100)
    27 LEFT: 54 (0x00000036) range: (0,100)
    28 TV_FORMAT: NTSC-M
    29 supported: NTSC-M NTSC-443 NTSC-J PAL-M
    30 PAL-N PAL

The interesting line is 3 which indicates that my "dummy" mode is activated for the VGA output.

PS: I used a 1280x800 mode because this is the resolution of my laptop panel and, somehow, using a smaller resolution caused my gnome panels to be resized.