Proportional Printing

(from Your Spectrum 20, November 1985)








OUT OF ALL PROPORTION





Normal Speccy printing is ugly, ugly, ugly and


boring, boring, boring. Here's shaped crusader


Tony 'Slim' Samuels with a pretty neat


alternative!








No-one could say that the way the Speccy PRINTs is


the most beautiful in the world. The problem is


that the screen is divided into 32 character


columns and every character always takes up the


same amount of space on the screen. Hardly news


and not the kind of thing that bothers us hacks at


all. But it's a bit of a shock for all those poor


misdirected human beings out there in the real


world.





Now take a close look at these words in YS, You'll


see that thin characters like I and 1 take up a


lot less space than fat ones like M and W. This is


our secret way of making sure you can read and


re-read YS from cover to cover at no risk to your


eyesight. Who says we don't look after you?





So how's about a little bit of machine code to


print properly using this sneaky proportional


printing idea? Not only will any program you write


using it look really nice and be very pleasant to


use but you get the added benefit of printing at


any pixel position on the screen and so stuff far


more than 32 characters on every line. Choose thin


words and you'll get more than 100 characters per


line! Proportional printing is therefore ideal for


any program with lots of text in it - databases,


word processors and so on.








GOTO LPRINT





To make life even easier, the print program here


becomes part of Speccy Basic by taking over the


LPRINT command. The syntax is the same except you


can now use the AT command if you like. The


program doesn't like INK and PAPER control codes


but it will print in whatever permanent colours


you've set with INK and PAPER. Once you've got the


routine loaded, the command, LPRINT AT 0,0; "Your


Spectrum" will print "Your Spectrum"


proportionally spaced in the top left of your


screen. All proportional printing is done as if


OVER 1 was set so you've got to be careful only to


print on blank bits of screen or else the result


will be more of a mess than the usual PRINT


command!








GET LOADED





To get your own printing going, you're going to


have to type in the proportional print program and


either the character set given here or one of your


own design. If you've got an assembler, you can go


to work on the assembly listing. Otherwise, you'll


have to type in and use the hex loader provided.


Once that's in, use the hex loader to enter the


proportional character set itself. Done all that?


Wow, you're getting really quick! Okay, best


remember to save the whole shebang as one lump


with:





SAVE "PROPSYS" CODE 64200,1150.





Now, whenever you get the urge, you can set up the


whole thing with:





CLEAR 64199: LOAD "PROPSYS" CODE: RANDOMIZE USR


65000





LPRINT ; will go on working until you do a NEW.


You can get it back afterwards with another


RANDOMIZE USR 65000.





The Speccy's got 96 printing characters from space


(CHR$(32) to the copyright symbol CHR$(127)). Each


of these is defined just like a UDG using 8 bytes.


A proportional character set is done in a similar


way except the first byte of each definition is


used to tell the print program how wide the


character is, so that it can start the next


character just after it.





To work out this byte, just set those bits that


aren't used by the character to 1 and leave the


rest at 0. If your character is four bits wide,


the bits 8,7,6,5 and 4 should all be 0 (bit 4 is 0


so that there's a one pixel gap between this


character and the next) and bits 0,1 and 2 should


be 1. Simple really! And I've included a little


font designer listing opposite so you can get


started right away. There, who says I'm just a


pretty face?











SHAPIN' UP





You'll find here all the code you need to get


proportional printing up and running on your


Speccy. Tony's also provided a designer program,


so if you're not happy with his creative


characters then you can knock up your own. If


you're going for the minimum typing job, then


you'll only need to enter three parts. The Hex


Loader (which enters the code), the Proper Print


machine code listing (using either our Hex Loader


or your own assembler package) and finally the


Character Set code using the Hex Loader program.











A HEX FOR YOU





In case you're wondering, this is a hex loader - a


program to provide hours and hours of endless


entering fun for all the family. To use it, type


it in and SAVE it and then enter the print program


by typing in each line of hex in the second column


of the main listing (one byte at a time) starting


from address 65000. When you've finished type xx.


The checksum should come to 45760 if you've got it


right. Next, use the loader to enter the


proportional character set. It starts at 64200 and


the checksum should come to 64743. Don't forget to


save it all with SAVE "PROPSYS" CODE 64200,1150 .











PROPER PRINT





This is it - the machine code program that,


coupled with a character set at 64200, prints like


magic on your Speccy. If you've got an assembler


or monitor, you can start straight away. Otherwise


nip ahead and type in the hex loader and come back


when it's running.





Start the routine at 65000 and declare some


labels.





Reset the printing position to the top left of the


screen.





Change the pointer to the LPRINT routine in the


CHANS table to point to the proportional printing


routine.





Save all the registers, call the printing routine,


put back all the registers again and leap back to


the operating system.





Look to see if last character was a control code


22 - the code for AT.





If the current character is an AT control code,


set the ATFLG to indicate that the next two codes


dealt with will be the X and Y positions for the


print.





If the last character was an AT then fetch the X


and Y co-ordinates and move to the new printing


position.





If the current character is a Return control code,


move down 8 pixels and open channel 2 to deal with


nasty INK and PAPER control codes.





Burp! If the character is not between 32 and 127


then print a question mark instead.





Figure out where the character's definition is


stored in memory.





Store the first byte of the character (the width


indicator) and stick a zero byte in its place.





We're getting there! Load CRADD with the address


of the seventh byte of the character, check the


character will fit on the screen and calculate the


address in the display file where the character


will be printed.





Rotate the character definition into the correct


pixel position, place it on the screen one byte at


a time and make sure each byte is in the right


colour.





Get the width indicator byte and put it back at


the start of the character definition. Then move


right the correct number of pixels for the


character just printed.





Reserve a bit of space for some variables.





Here's a handy routine that sets HL to point to


the next pixel line up in the display file.





Restore the width indicator byte to the first byte


of the character definition and generate an Out of


Screen error.





Check if the character to be printed will fit on


this line - if it doesn't, move down 8 pixels and


back to the left hand side of the screen.





And another useful routine - it calculates the


relevant address in the attributes file from a


given display file address and stores the value of


ATTRP (the permanent PAPER and INK colours) in it.





That's all folks!











CHARACTER SET





Here's the info for proportionally spaces


characters - all 96 of them! Grab the hex loader


and get going ...











FONT DESIGNER





You can use this either for the proportional


printing program or for the Speccy's normal


characters. Q, A, O and P move the cursor around -


give Troubleshootin' Pete a ring if you can't work


out which does which direction! To set a pixel use


M and to turn one off use N. F stores the design


on the grid in memory as any particular character


you want, D displays any character, U shows the


whole character set and S and J save and load the


whole lot for you. Once you've saved a new set,


you can load it into the proportional print


program with LOAD "name" CODE 64200. Away you go


...











DEMO LISTING JOB





If you're still confused about life, death and the


meaning of proportional printing, try out this


major new adventure program once you've got


PROPSYS working. Cor, it's even harder than Castle


Rathbone! Just so you can see how awful Speccy


printing is, the magic word xyzzy will flip you


between the two types of printing.











Before ... and after. The difference, as you can


see, is quite dramatic. Not only is the


proportional text more pleasing to look at - it's


also easier to read!