Custom VESA mode does not work for 4bit resolution

[ErikB]

I'm trying to add custom VESA mode 1400x1050x4.

I'm using command VBoxManage setextradata "WinXp" "CustomVideoMode1" "1400x1050x4"

and the line

<ExtraDataItem name="CustomVideoMode1" value="1400x1050x4"/>

is created in WinXp.vbox correctly.

When I try to start the virtual machine VB gives me the VERR_VGA_INVALID_CUSTOM_MODE error.

Note, that 1400x1050x8, 16, 24 and 32 work very fine, but I'm interested in 4bit colors.

A small modification in 'VBox/Devices/Graphics/DevVGA.cpp' will probably solve this problem.

Please refer to the attached 'Custom VESA mode 4bit resolution.png' for a possible solution.