[cc65] Re: New 80 col switch API

From: Jonathan Graham Harston <jgh1arcade.demon.co.uk>
Date: 2009-09-08 00:43:25
> Message-ID: <f97798c20909070031t214e42e3k470da093a972b265@mail.gmail.com>
Oliver Schmidt wrote:
> From my understanding non of the cc65 targets can produce arbitrary
> numbers of lines and columns. Having the users provide numbers
> directly enforces the impression that many numbers works.
The BBC can have 20, 40 or 80 columns and 25 or 32 rows.
> to come up with here. A replacement for toggle_videomode should still
What does toggle_videomode do?
> #define VIDEOMODE_40COL 0x??
> #define VIDEOMODE_80COL 0x??
> These two defines should be available for all targets supporting this
> type of switching to allow for target independent programming.
Exactly, viz:
#define VIDEOMODE_40COL 0x28   /* ie, 40 */
#define VIDEOMODE_80COL 0x50   /* ie, 80 */
is expanded by the preprocessor to
which is the same as
which by Oliver's scheme is: select a 40-column screen mode, let
the system decide how many rows it has, any by my scheme is: select
a 40-column screen mode, I don't care how many rows it has, let the
system decide how many rows it has.
Targetting the BBC, that becomes:
; videomode(int size)
; -------------------
; x=lsb size  [1]
lda #22
jsw osrwch
lda #128
cpx #60
bcs ~videomode1
lda #131
jmp oswrch
[1] Small-C passes b0-b7 of the top parameters in X, I haven't
checked how cc65 does it. Adjust to fit.
> #define VIDEOMODE_40x25 0x??
> #define VIDEOMODE_80x25 0x??
> #define VIDEOMODE_??x?? 0x??
You #define whatever you normally need for the implementation.
Having the API pass a parameter that has some relationship to what
it represents gives the code more sense, consistancy and future
> least two of them with values identical to VIDEOMODE_40COL and
The default standard implementation would just need
#define VIDEOMODE_40COL 40 and #define VIDEOMODE_80COL 80.
J.G.Harston - jgh@arcade.demon.co.uk - mdfs.net/User/JGH
A Review of Sheffield City Council's Members' Allowances Scheme
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Received on Tue Sep 8 01:01:21 2009

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