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SWI / BASIC command to read number of Pixels in a screen mode

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  SWI / BASIC command to read number of Pixels in a screen mode Michael <michaelremerton@gmail.com> - 2011-09-27 14:49 -0700
    Re: SWI / BASIC command to read number of Pixels in a screen mode Alex Macfarlane Smith <nospam@archifishal.co.uk> - 2011-09-27 22:51 +0100
      Re: SWI / BASIC command to read number of Pixels in a screen mode Michael <michaelremerton@gmail.com> - 2011-09-27 15:02 -0700
        Re: SWI / BASIC command to read number of Pixels in a screen mode Michael <michaelremerton@gmail.com> - 2011-09-27 15:18 -0700
          Re: SWI / BASIC command to read number of Pixels in a screen mode Martin Bazley <martin.bazley@blueyonder.co.uk> - 2011-09-27 23:36 +0100
        Re: SWI / BASIC command to read number of Pixels in a screen mode Martin Bazley <martin.bazley@blueyonder.co.uk> - 2011-09-27 23:34 +0100
          Re: SWI / BASIC command to read number of Pixels in a screen mode Michael <michaelremerton@gmail.com> - 2011-09-27 16:10 -0700
      Re: SWI / BASIC command to read number of Pixels in a screen mode Martin Bazley <martin.bazley@blueyonder.co.uk> - 2011-09-27 23:19 +0100
        Re: SWI / BASIC command to read number of Pixels in a screen mode Michael <michaelremerton@gmail.com> - 2011-09-27 16:14 -0700
          Re: SWI / BASIC command to read number of Pixels in a screen mode Steve Drain <steve@kappa.me.uk> - 2011-09-28 11:33 +0100
            Re: SWI / BASIC command to read number of Pixels in a screen mode Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2011-09-28 17:27 +0200
            Re: SWI / BASIC command to read number of Pixels in a screen mode Michael <michaelremerton@gmail.com> - 2011-09-28 18:57 -0700
          Re: SWI / BASIC command to read number of Pixels in a screen mode Gazza <usenet@garethlock.com> - 2011-10-18 16:12 -0700
            Re: SWI / BASIC command to read number of Pixels in a screen mode "Ste (news)" <steve@revi11.plus.com> - 2011-10-25 14:33 +0100
        Re: SWI / BASIC command to read number of Pixels in a screen mode Martin Wuerthner <spamtrap@mw-software.com> - 2011-09-28 10:47 +0200
          Re: SWI / BASIC command to read number of Pixels in a screen mode Steve Drain <steve@kappa.me.uk> - 2011-09-28 12:02 +0100
            Re: SWI / BASIC command to read number of Pixels in a screen mode Steve Drain <steve@kappa.me.uk> - 2011-09-28 12:09 +0100
              Re: SWI / BASIC command to read number of Pixels in a screen mode "Ste (news)" <steve@revi11.plus.com> - 2011-09-28 15:13 +0100
                Re: SWI / BASIC command to read number of Pixels in a screen mode Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2011-09-28 17:36 +0200
                  Re: SWI / BASIC command to read number of Pixels in a screen mode Steve Drain <steve@kappa.me.uk> - 2011-09-28 17:32 +0100
          Re: SWI / BASIC command to read number of Pixels in a screen mode Martin <News03@avisoft.f9.co.uk> - 2011-09-28 12:55 +0100
          Re: SWI / BASIC command to read number of Pixels in a screen mode Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2011-09-28 17:34 +0200
        Re: SWI / BASIC command to read number of Pixels in a screen mode Gazza <usenet@garethlock.com> - 2011-10-18 16:10 -0700
          Re: SWI / BASIC command to read number of Pixels in a screen mode Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2011-10-19 06:49 +0200
            Re: SWI / BASIC command to read number of Pixels in a screen mode Steve Drain <steve@kappa.me.uk> - 2011-10-19 10:19 +0100
            Re: SWI / BASIC command to read number of Pixels in a screen mode Erik G <erikg@noname.invalid> - 2011-10-19 15:24 +0200
              Re: SWI / BASIC command to read number of Pixels in a screen mode Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2011-10-19 19:47 +0200
                Re: SWI / BASIC command to read number of Pixels in a screen mode druck <news@druck.org.uk> - 2011-10-19 20:36 +0100
                  Re: SWI / BASIC command to read number of Pixels in a screen mode Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2011-10-20 17:40 +0200
                    Re: SWI / BASIC command to read number of Pixels in a screen mode druck <news@druck.org.uk> - 2011-10-20 20:13 +0100
    Re: SWI / BASIC command to read number of Pixels in a screen mode Chris Johnson <chrisjohnson+news@spamcop.net> - 2011-09-27 23:21 +0100
    Re: SWI / BASIC command to read number of Pixels in a screen mode Bryan Hogan <spam@nowhere.invalid> - 2011-09-28 01:49 +0100
      Re: SWI / BASIC command to read number of Pixels in a screen mode Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2011-09-28 18:22 +0200
        Re: SWI / BASIC command to read number of Pixels in a screen mode Michael <michaelremerton@gmail.com> - 2011-09-28 19:12 -0700
          Re: SWI / BASIC command to read number of Pixels in a screen mode "Ste (news)" <steve@revi11.plus.com> - 2011-09-29 12:42 +0100
            Re: SWI / BASIC command to read number of Pixels in a screen mode Steve Drain <steve@kappa.me.uk> - 2011-09-29 16:14 +0100
              Re: SWI / BASIC command to read number of Pixels in a screen mode "Ste (news)" <steve@revi11.plus.com> - 2011-09-30 00:12 +0100
                Re: SWI / BASIC command to read number of Pixels in a screen mode Steve Drain <steve@kappa.me.uk> - 2011-09-30 10:48 +0100

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#774 — SWI / BASIC command to read number of Pixels in a screen mode

Hi All,

I have been traversing the Strong help OS Manual, looking for a suitable SWI to return the width of a MODE MODE'd Screen (basically so I run in the same resolution the Machine is already in).

Reason for this: scale things on the screen suitably.

I had thought OS_ScreenMode would have done it but nope!

Cheers in advance :@)

Michael

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#775

On 27/09/2011 22:49, Michael wrote:
> Hi All,
>
> I have been traversing the Strong help OS Manual, looking for a suitable SWI to return the width of a MODE MODE'd Screen (basically so I run in the same resolution the Machine is already in).
>
> Reason for this: scale things on the screen suitably.
>
> I had thought OS_ScreenMode would have done it but nope!
>
> Cheers in advance :@)
>
> Michael

I think it might be OS_ReadVduVariables, although I can't remember the 
number you need for it.

eg.

DIM b% 8

b%!0=148
b%!4=-1
SYS "OS_ReadVduVariables",b%,b%

will give you the start address of the screen in b%!0. Now you just need 
to find the magic number that isn't 148 to be the width of the screen :)

Alex.

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#776

> I think it might be OS_ReadVduVariables, although I can't remember the 
> number you need for it.

Rather amasingly, I had just looked at that when your post popped up!

 
> eg.
> 
> DIM b% 8
> 
> b%!0=148
> b%!4=-1
> SYS "OS_ReadVduVariables",b%,b%
> 
> will give you the start address of the screen in b%!0. Now you just need 
> to find the magic number that isn't 148 to be the width of the screen :)


Re-reading it after your post, slight modfication:

DIM b% 8
b%!4=-1
SYS "OS_ReadVduVariables",11,b%

width% = b%!0

SYS "OS_ReadVduVariables",12,b%

height% = b%!0

Cheers :@)

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#779

scratch that:


DIM b% 8
b%!0 = 11
b%!4=-1
SYS "OS_ReadVduVariables",b%,b%

width% = b%!0

b%!0 = 12

SYS "OS_ReadVduVariables",b%,b%

height% = b%!0

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#781

The following bytes were arranged on 27 Sep 2011 by Michael :

> DIM b% 8
> b%!0 = 11
> b%!4=-1
> SYS "OS_ReadVduVariables",b%,b%
>
> width% = b%!0
>
> b%!0 = 12
>
> SYS "OS_ReadVduVariables",b%,b%
>
> height% = b%!0

That's still two calls to the SWI, which is unnecessary because it's not
OS_ReadModeVariable and can return values for more than one variable at
once.  See my earlier post.

Variables 11 and 12 are values in pixels, not used by any RISC OS
plotting routine.  You need the eigen-factors, variables 4 and 5, as
well, to convert them to OS units.

-- 
  __<^>__   "Your pet, our passion." - Purina
 / _   _ \  "Your potential, our passion." - Microsoft, a few months later
( ( |_| ) )
 \_>   <_/  ======================= Martin Bazley ==========================

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#780

The following bytes were arranged on 27 Sep 2011 by Michael :

> DIM b% 8
> b%!4=-1
> SYS "OS_ReadVduVariables",11,b%

DON'T do that!  Best case is oflas, worst case is a data abort!

Both registers are pointers to blocks - you can't just pass numbers!

-- 
  __<^>__   "Start off every day with a smile and get it over with."
 / _   _ \  - W.C. Fields
( ( |_| ) )
 \_>   <_/  ======================= Martin Bazley ==========================

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#782

On Tuesday, September 27, 2011 11:34:23 PM UTC+1, Martin Bazley wrote:
> The following bytes were arranged on 27 Sep 2011 by Michael :
> 
> > DIM b% 8
> > b%!4=-1
> > SYS "OS_ReadVduVariables",11,b%
> 
> DON'T do that!  Best case is oflas, worst case is a data abort!

Oddly, an obsure number!

> Both registers are pointers to blocks - you can't just pass numbers!

I had realised I had typed it back into Chrome wrong! :@D

Nothing like a good bit of late night programming ;@)

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#778

The following bytes were arranged on 27 Sep 2011 by Alex Macfarlane Smith :

> On 27/09/2011 22:49, Michael wrote:
> > I have been traversing the Strong help OS Manual, looking for a
> > suitable SWI to return the width of a MODE MODE'd Screen (basically
> > so I run in the same resolution the Machine is already in).
>
> I think it might be OS_ReadVduVariables, although I can't remember the
> number you need for it.

DIM b% 19
!b%=11:REM XWindLimit
b%!4=12:REM YWindLimit
b%!8=4:REM XEigFactor
b%!12=5:REM YEigFactor
b%!16=-1:REM terminator
SYS "OS_ReadVduVariables",b%,b%
screen_width%=!b%<<b%!8:REM in OS units
screen_height%=b%!4<<b%!12

Testing performed on above routine: no more than everything else ever
posted to csap late at night.  Warranty given: none.

-- 
  __<^>__   "Did you know that polar bears stay white all year round? ...The
 / _   _ \  white colour makes them less visible to the seals and penguins they
( ( |_| ) ) hunt."  - Nelson Thornes AQA-endorsed GCSE science textbook
 \_>   <_/  ======================= Martin Bazley ==========================

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#783

> > On 27/09/2011 22:49, Michael wrote:
> > > I have been traversing the Strong help OS Manual, looking for a
> > > suitable SWI to return the width of a MODE MODE'd Screen (basically
> > > so I run in the same resolution the Machine is already in).
> >
> > I think it might be OS_ReadVduVariables, although I can't remember the
> > number you need for it.
> 
> DIM b% 19
> !b%=11:REM XWindLimit
> b%!4=12:REM YWindLimit
> b%!8=4:REM XEigFactor
> b%!12=5:REM YEigFactor
> b%!16=-1:REM terminator
> SYS "OS_ReadVduVariables",b%,b%
> screen_width%=!b%<<b%!8:REM in OS units
> screen_height%=b%!4<<b%!12
> 


Typed up and in!

Cheers :@)

Out of curiosity, what is the << operator?

My BASIC 2.0 StrongHelp Manual doesn't appear to have operators in character form

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#786

On 28/09/2011 00:14, Michael wrote:
> Out of curiosity, what is the <<  operator?
>
> My BASIC 2.0 StrongHelp Manual doesn't appear to have operators in character form

Then you need the v3.xx manual at:

  http://www.kappa.me.uk/basic.htm

;-)

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#794

On 28/09/2011 12:33, Steve Drain wrote:

> Then you need the v3.xx manual at:
> http://www.kappa.me.uk/basic.htm

Great stuff. I was wondering if you'd updated since the BASIC-internals 
since the version I had from you circa 2001/2002. ;-)


Best wishes,

Rick.

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#801

> > My BASIC 2.0 StrongHelp Manual doesn't appear to have operators in character form
> 
> Then you need the v3.xx manual at:
> 
>   http://www.kappa.me.uk/basic.htm
> 
> ;-)

Downloaded :@)

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#889

On Sep 28, 12:14 am, Michael <michaelremer...@gmail.com> wrote:
> > > On 27/09/2011 22:49, Michael wrote:
> > > > I have been traversing the Strong help OS Manual, looking for a
> > > > suitable SWI to return the width of a MODE MODE'd Screen (basically
> > > > so I run in the same resolution the Machine is already in).
>
> > > I think it might be OS_ReadVduVariables, although I can't remember the
> > > number you need for it.
>
> > DIM b% 19
> > !b%=11:REM XWindLimit
> > b%!4=12:REM YWindLimit
> > b%!8=4:REM XEigFactor
> > b%!12=5:REM YEigFactor
> > b%!16=-1:REM terminator
> > SYS "OS_ReadVduVariables",b%,b%
> > screen_width%=!b%<<b%!8:REM in OS units
> > screen_height%=b%!4<<b%!12
>
> Typed up and in!
>
> Cheers :@)
>
> Out of curiosity, what is the << operator?
>
> My BASIC 2.0 StrongHelp Manual doesn't appear to have operators in character form- Hide quoted text -
>
> - Show quoted text -

Shift left I think... >> Is shift right.

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#927

In article
<a75fbd65-8f44-4076-8b75-8424abe99ca8@x20g2000vbl.googlegroups.com>,
   Gazza <usenet@garethlock.com> wrote:
> On Sep 28, 12:14 am, Michael <michaelremer...@gmail.com> wrote:
> > Out of curiosity, what is the << operator?
>
> Shift left I think... >> Is shift right.

_Logical_ shift left is << (i.e. zeros inserted in bottom positions)
_Logical_ shift right is >>> (i.e. zeros inserted in top positions)
_Arithmetic_ shift right is >> (i.e. the sign bit is extended down)

I'm sure this is also in the BASIC manuals...

  http://www.kappa.me.uk/basic.htm

is one example.

Steve

-- 
Steve Revill @ Home
Note: All opinions expressed herein are my own.

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#785

In message <87167f1952.martin@blueyonder.co.uk>
          Martin Bazley <martin.bazley@blueyonder.co.uk> wrote:

> The following bytes were arranged on 27 Sep 2011 by Alex Macfarlane Smith :

>> On 27/09/2011 22:49, Michael wrote:
>>> I have been traversing the Strong help OS Manual, looking for a
>>> suitable SWI to return the width of a MODE MODE'd Screen (basically
>>> so I run in the same resolution the Machine is already in).
>>
>> I think it might be OS_ReadVduVariables, although I can't remember the
>> number you need for it.

> DIM b% 19
> !b%=11:REM XWindLimit
> b%!4=12:REM YWindLimit
> b%!8=4:REM XEigFactor
> b%!12=5:REM YEigFactor
> b%!16=-1:REM terminator
> SYS "OS_ReadVduVariables",b%,b%
> screen_width%=!b%<<b%!8:REM in OS units
> screen_height%=b%!4<<b%!12

> Testing performed on above routine: no more than everything else ever
> posted to csap late at night.  Warranty given: none.

That code will miss a pixel in either direction. Oddly enough, 
variables 11 and 12 give the number of pixels *minus 1*.

So, you need :

screen_width%=((!b%) + 1)<<b%!8
screen_height%=((b%!4) + 1)<<b%!12

-- 
Martin
---------------------------------------------------------------------
Martin Wuerthner         MW Software      http://www.mw-software.com/
        RISC OS Software for Design, Printing and Publishing
---------------------------------------------------------------------

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#787

On 28/09/2011 09:47, Martin Wuerthner wrote:
> In message<87167f1952.martin@blueyonder.co.uk>
>            Martin Bazley<martin.bazley@blueyonder.co.uk>  wrote:
>
>> The following bytes were arranged on 27 Sep 2011 by Alex Macfarlane Smith :
>
>>> On 27/09/2011 22:49, Michael wrote:
>>>> I have been traversing the Strong help OS Manual, looking for a
>>>> suitable SWI to return the width of a MODE MODE'd Screen (basically
>>>> so I run in the same resolution the Machine is already in).
>>>
>>> I think it might be OS_ReadVduVariables, although I can't remember the
>>> number you need for it.
>
>> DIM b% 19
>> !b%=11:REM XWindLimit
>> b%!4=12:REM YWindLimit
>> b%!8=4:REM XEigFactor
>> b%!12=5:REM YEigFactor
>> b%!16=-1:REM terminator
>> SYS "OS_ReadVduVariables",b%,b%
>> screen_width%=!b%<<b%!8:REM in OS units
>> screen_height%=b%!4<<b%!12
>
>> Testing performed on above routine: no more than everything else ever
>> posted to csap late at night.  Warranty given: none.
>
> That code will miss a pixel in either direction. Oddly enough,
> variables 11 and 12 give the number of pixels *minus 1*.
>
> So, you need :
>
> screen_width%=((!b%) + 1)<<b%!8
> screen_height%=((b%!4) + 1)<<b%!12


With Basalt:

   VDU READ 4 TO xeig%,yeig%; 11 TO xlim%,ylim%
   width%=xlim%+1<<xeig%
   height%=ylim%+1<<yeig%

or

   width%=VDU(11)+1<<VDU(4)
   height%=VDU(12)+1<<VDU(5)

Note that the operator << has lowest priority.

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#788

On 28/09/2011 12:02, Steve Drain wrote:
>
> width%=VDU(11)+1<<VDU(4)
> height%=VDU(12)+1<<VDU(5)
>
> Note that the operator << has lowest priority.
>

I think this also works with RO5 BASIC:

  width%=VDU11+1<<VDU4
  height%=VDU12+1<<VDU5

but I do not have that to test.

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#790

In article <HgDgq.1930$jz6.879@newsfe18.ams2>,
   Steve Drain <steve@kappa.me.uk> wrote:
> I think this also works with RO5 BASIC:
>
>   width%=VDU11+1<<VDU4
>   height%=VDU12+1<<VDU5
>
> but I do not have that to test.

That's correct and you've saved me typing it.

Note the operator precedence there; VDU11+1 is (VDU 11) and not VDU(11+1).

Still, I'd always use braces for clarity. E.g.

  width_os% = ((VDU 11) + 1) << VDU 4

Ta,

Steve

-- 
Steve Revill @ Home
Note: All opinions expressed herein are my own.

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#796

On 28/09/2011 16:13, Ste (news) wrote:

>> I think this also works with RO5 BASIC:
>>    width%=VDU11+1<<VDU4
>>    height%=VDU12+1<<VDU5

> That's correct and you've saved me typing it.

But perhaps best to use the "legal" method, unless you intend only to 
support machines running the RO5 dialect of BASIC?


Best wishes,

Rick.

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#798

On 28/09/2011 16:36, Rick Murray wrote:
> On 28/09/2011 16:13, Ste (news) wrote:
>
>>> I think this also works with RO5 BASIC:
>>> width%=VDU11+1<<VDU4
>>> height%=VDU12+1<<VDU5
>
>> That's correct and you've saved me typing it.
>
> But perhaps best to use the "legal" method, unless you intend only to
> support machines running the RO5 dialect of BASIC?

<plug>
Or use Basalt and its syntax with all versions. ;-)
</plug>

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