Difference between revisions of "VDUV"
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[[Category:MOS API]] | [[Category:MOS API]] | ||
==Specification== | ==Specification== | ||
| − | This vector is called by the VDU drivers to pass on unknown VDU sequences | + | This vector is called by the VDU drivers to pass on unknown VDU sequences from |
| − | + | [[VDU 23]] and [[VDU 25]] (PLOT). It can be used to implement extra PLOT calls, | |
| − | PLOT functions in non-graphics MODEs, and additional VDU 23 calls. The | + | PLOT functions in non-graphics MODEs, and additional VDU 23 calls. The Graphics |
| − | + | Extension ROM claims VDUV to provide its additional VDU calls. PLOT calls &F0-&FF | |
| − | PLOT calls &F0-&FF and VDU 23 calls 28-31 are always passed to VDUV. | + | and VDU 23 calls 28-31 are always passed to VDUV. |
On entry: | On entry: | ||
| Line 35: | Line 35: | ||
.newvduvec | .newvduvec | ||
BCS plotexit :\ VDU 23,nn | BCS plotexit :\ VDU 23,nn | ||
| − | + | \ Start by converting the coordinates | |
| − | + | LDY &361:PHA:BNE plotcoords :\ already adjusted | |
| − | + | LDY #&0C:AND #4:BNE plotabs :\ plot absolute, add origin | |
| − | + | LDY #&24 :\ plot relative, add last | |
| − | |||
.plotabs | .plotabs | ||
| + | LDX #&20:JSR plotadd :\ plot=plot+base | ||
\ If needed, scale the coordinates here | \ If needed, scale the coordinates here | ||
\ For instance, this scales X from 0-2N to 0-N | \ For instance, this scales X from 0-2N to 0-N | ||
Latest revision as of 15:05, 26 September 2024
Specification
This vector is called by the VDU drivers to pass on unknown VDU sequences from VDU 23 and VDU 25 (PLOT). It can be used to implement extra PLOT calls, PLOT functions in non-graphics MODEs, and additional VDU 23 calls. The Graphics Extension ROM claims VDUV to provide its additional VDU calls. PLOT calls &F0-&FF and VDU 23 calls 28-31 are always passed to VDUV.
On entry:
CC=Unknown PLOT command
CS=Unknown VDU 23 sequence
A=PLOT number or VDU 23 number
All registers can be trashed by the handler
CC - PLOT command
&031F = PLOT number, also in A &0320,1 = PLOT X &0322,3 = PLOT Y &0324,5 = last X &0326,7 = last Y &0314,5 = previous X &0316,7 = previous Y &0361 = 0:coords not converted, <>0:coords already adjusted
The various VDU workspace locations contain the coordinates of the PLOT command and the previous locations to use when drawing lines or shapes. On entry, if &0361 contains &00 the coordinates need to be translated by adding to the graphics origin and converting relative coordinates to absolute coordinates. If &0361 is non-zero, the coordinates have already been converted.
Before exit, the coordinates need be be cycled, with LAST copied to PREVIOUS and PLOT copied to LAST, ready for the next PLOT call.
The following is skeleton code.
.newvduvec BCS plotexit :\ VDU 23,nn \ Start by converting the coordinates LDY &361:PHA:BNE plotcoords :\ already adjusted LDY #&0C:AND #4:BNE plotabs :\ plot absolute, add origin LDY #&24 :\ plot relative, add last .plotabs LDX #&20:JSR plotadd :\ plot=plot+base \ If needed, scale the coordinates here \ For instance, this scales X from 0-2N to 0-N LDX #0 LDA &321,X:ASL A:ROR &321,X:ROR &320,X \ .plotcoords PLA:AND #3:BEQ plotupdate :\ %xxxxxx00 - MOVE : \ PERFORM THE PLOT ACTION HERE : .plotupdate LDX #3 .plotuplp LDA &324,X:STA &314,X :\ LAST->PREV LDA &320,X:STA &324,X :\ PLOT->LAST DEX:BPL plotuplp .plotexit RTS : .plotadd JSR plotadd2:INX:INX:INY:INY .plotadd2 CLC LDA &300,X:ADC &300,Y:STA &300,X LDA &301,X:ADC &301,Y:STA &301,X RTS
See mdfs.net/blah/blah for sample demo code.
CS - VDU 23 sequence
&031B command, also in A &031C parameter 1 &031D parameter 2 &031E parameter 3 &031F parameter 4 &0320 parameter 5 &0321 parameter 6 &0322 parameter 7 &0323 parameter 8
