I implemented a bunch of commands for BT81x and I am in the process of testing them.
There is this new OPT_FILL for CMD_TEXT and CMD_BUTTON and the pixel-value for is setup with CMD_FILLWIDTH.
There is however no value for it given in the table 5.10 of the BT81x Series Programming Guide.
The EVE Screen Editor v3.1.2 is also of no help because it ignores the option and when I exported a simple test-project
I could not find OPT_FILL in there either.
As far as I can tell there are also no BT81x examples available to the public.
Fortunately I have been given the source code for one of the examples that were shown
at the Embedded World in Nürnberg, so here you go:
#define OPT_FILL 8192UL
I have tested it with this define and at least for CMD_TEXT it works just fine.