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^1                        PROGRAMMING HINTS AND TIPS.

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^2 Here     Are     The     Latest     Totally     Amos    Top    Tips!

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^6 When  you need to load something from disk, it is a good idea to put
^6the filename inside a string and then check to see if the file exists
^6in the following way.

^2 FIL$="Save.game"
^2 If Exist (FIL$)
^2 Load F$
^2 Else

^6 Here you would put in an error trap to tell you if the file does not
^6exist

^2 End If

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^4  How  many  times  have  you  finished a program, especially one for
^4children,  only  to find that the user clicks the mouse button on the
^4wrong thing at the wrong time?

^4 This can cause a program to crash, or something extremely unexpected
^4to  happen  if the mouse is clicked, for example, during an animation
^4sequence.

^4 The answer is simple, freeze the mouse!

^4 Thanks  to  Paul  Townsend  for  sorting  out  this problem when the
^4situation arouse during one of our projects.

^4 You use Limit Mouse to do this, but using the same beginning and end
^4coordinates in the following manner.

^4 This will freeze the mouse at a point roughly centre of the screen.

^2 Limit Mouse 272,162 to 272,162

^4 Any coordinates will work as long as the two sets of coordinates are
^4identical.   We had previously assumed that this would be illegal and
^4so  had  never  tried it.  This proves the point that you cannot find
^4out if something wiill work until you try it!

^2 Note  that  all  the coordinates are hardware coordinates not screen
^2coordinates.  This adds 128 to the X axis and 50 to the Y axis.

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^1For more advanced coders.....

^1 If you want to open Workbench from inside Amos, use the following.

^2 A=Intcall(-210)

^1To close it again

^2 A=Intcall(-78)

^1Note.   If  you  close  Workbench with this method, and workbench has
^1some  windows  open,  when you open up Workbench again, these windows
^1will be as you left them.

^2 This tip comes courtesy of Simon Nicoll.

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^6 This  a  routine  for  Ctext users which will centre a line of text.
^6With a little alteration it can be used with the normal Text command.

^2 PRNT:
^2 NBR=Plen(M$)
^2 Ctext160-(NBR/2),YT,M$
^2 Return

^6 Call this subroutine as follows

^2 YT=100
^2 M$="Hello Totally Amos Readers!"
^2 Gosub PRNT
 
^6 You  could  also  put  in  a Cls command before the Ctext command to
^6clear the line the text is on.

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^4 This tip is for those of you who have really got to grips with using
^4Intcall and Execall.

^4 This tip comes again from Simon Nicoll, and comes with a programers
^4health  warning!!!!   If you don't know what you are doing, then make
^4sure  that you are messing about with a backup of your program or you
^4could  end  up  with  a totally useless program!  Read on to find out
^4what it does and what could go wrong!!

^4 The two routines are 

^2 Dreg(0)=Execall(-132)
^2 Dreg(0)=Execall(-138)

^4 These  respectively  turn  multi-tasking  off  and on.  They do have
^4certain  limitations,  but  the  benefits  of using them properly far
^4outweigh these according to the type off game you are writing.

^4 One  of the main faults is that when you use Execall(-132) to switch
^4off  multi-tasking, you lose all access to the keyboard, according to
^4which  version  of  Amos you are using, you will also lose the use of
^4the  mouse  until the program has been compiled.  In all cases, the
^4keyboard is disabled.  It has no effect on the Joystick.

^4 The  type  of game where it would have no use is a shoot'em up where
^4the  keyboard  is needed to gain access to extra weopons or a `Pause'
^4feature in addition to movement with the joystick.

^4 On  the other hand, if you are writing a game that contains animated
^4sequences with no keyboard interaction, then this one is for you.

^4 When  using  AMAL, under certain circumstances, you can get a little
^4shudder  which is difficult to get rid of.  From what we've seen over
^4the  past few weeks since learning about this tip, this shudder seems
^4to  have  been  completely  removed.   As an added bonus, the program
^4appears to have speeded up by about 10%.

^4 All you have to do is turn off the keyboard when multi-tasking isn't
^4needed, and turn it back on when it is.

^4 It  is strongly recommended that this routine is ^2NOT ^4attached until
^4all  developing of your program has been done because if you run your
^4program in developing time and come up with an error, all you will be
^4left  with  is  a useless disk as you will not have ANY access to the
^4keyboard to correct the error.

^2 The only way out here is a 3 key reset.

^3                           YOU HAVE BEEN WARNED!

^4 This is a marvellous facility if used correctly, thanks Simon.


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^1 Tiny Tip

^1 To automatically toggle a variable from 0 to 1, use the following

^2 T=1-T

^1 Every pass of the loop will change the value of T.

^1 Thanks to Aaron Fothergill for this one!

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^5 To  save  wear and tear on your keyboard and your pinkies when using
^5the  Fade  or  palette  commands  and all the parameters are the same
^5colour.

^2 For example for a 16 colour screen
^2 Palette
^2$FFF,$FFF,$FFF,$FFF,$FFF,$FFF,$FFF,$FFF,$FFF,$FFF,$FFF,$FFF,$FFF,
^2$FFF,$FFF,$FFF
 
^2do F=$FFF then all you have to type is

^2 Palette F,F,F,F,F,F,F,F,F,F,F,F,F,F,F,F

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^2 Proc*NBR*: rem Use square brackets in place of `*'
^2 Repeat
^2 Add CV,1
^2 K$=Inkey$
^2 If K$=Inkey$
^2 If k$<>" ":CV=NBR:End If
^2 Wait 1
^2 Until CV=NBR
^2 End Proc

^1 This  procedure  makes  the  computer  sit  and wait for a specified
^1amount  of  time  as contained in the variable NBR, or until the user
^1hits a key.
^1 It  can  also  be  used  to  check  for  a click of a mouse key or a
^1joystick quite easily.

^1eg for the mouse

^2 If Mouse Key<>0:CV=NBR:End If

^1 The call to this procedure would be WT[30], for example.

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^4 This tip will give you back about 10k in run time.

^4 Set  the Sprite Buffer to 18, but only if you are not using sprites.
^4You  will  notice  that  your  `Amos' sprite has disappeared from the
^4editor  screen  as now you cannot display sprites more than 16 pixels
^4deep.

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