Minimal library to draw text

[llopis]

I'm thinking of creating a diagnostic program that would be 100% in ROM. I'd love to find out a library/routine to draw text on screen. It can be super simple, hardwired fonts, no fancy colors or anything. I could do it myself, but I'm sure that must be done somewhere already. Can someone point me in the right direction?

[LambdaMikel]

If we do, are you going to acknowledge help that is offered to you, are you going to ignore the replies?

[fgbrain]

Its easy to make your own little text toutine.
Decide for which screen mode first.
Then grab the font you are using for texts
The shortest code will use mode 2 (1 byte per character line)

[llopis]

If we do, are you going to acknowledge help that is offered to you, are you going to ignore the replies?

I'm not sure I follow. This would be for an open source project that I would put up on GitHub. I would acknowledge all significant contributions.


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[llopis]

Its easy to make your own little text toutine.
Decide for which screen mode first.
Then grab the font you are using for texts
The shortest code will use mode 2 (1 byte per character line)

Right. I probably did that a bunch of times in the last. I was hoping not to have to write that myself again :-)


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[LambdaMikel]

Then grab the font you are using for texts

Maybe just use the firmware routines?

[llopis]

Maybe just use the firmware routines?

I could use the firmware routines to copy the font, but I want this routine to be completely independent of the system firmware (I realize it wasn't clear in my initial description). This is for a diagnostics program, so I want it to work even in the case of a faulty system ROM.

[HAL6128]

just easily do (for MODE 2):

Code Select Expand

org &4000   ;just an example... could be somewhere else e.g. &00 in lower ROM ??

ld bc,&7f8e
out (c),c    ;enable mode 2 / disable upper and lower roms paging

ld d,&08 ;number of fine line
ld ix,pattern ;address of bit pattern
ld iy,&c030 ;address of screen ram
ld bc,&800 ;next line of screen address
.l1
ld a,(ix+&00)
ld (iy+&00),a
inc ix
add iy,bc
dec d
jp nz,l1
ret

.pattern
defb 16,16,40,40,68,124,130,130 ; just a simple "A"