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Elite on the BBC Micro

Flight: SIGHT (6502SP version)

Name: SIGHT [View in context] Type: Subroutine [Compare versions] Category: Flight Summary: Draw the laser crosshairs
.SIGHT LDY VIEW \ Fetch the laser power for our new view LDA LASER,Y BEQ LO2 \ If it is zero (i.e. there is no laser fitted to this \ view), jump to LO2 to return from the subroutine (as \ LO2 contains an RTS) LDA #YELLOW \ Send a #SETCOL YELLOW command to the I/O processor to JSR DOCOL \ switch to colour 1, which is yellow in the space view LDA #128 \ Set QQ19 to the x-coordinate of the centre of the STA QQ19 \ screen LDA #Y-24 \ Set QQ19+1 to the y-coordinate of the centre of the STA QQ19+1 \ screen, minus 24 (because TT15 will add 24 to the \ coordinate when it draws the crosshairs) LDA #20 \ Set QQ19+2 to size 20 for the crosshairs size STA QQ19+2 JSR TT15b \ Call TT15b to draw crosshairs of size 20 just to the \ left of the middle of the screen, in the current \ colour (yellow) LDA #10 \ Set QQ19+2 to size 10 for the crosshairs size STA QQ19+2 JMP TT15b \ Call TT15b to draw crosshairs of size 10 at the same \ location, which will remove the centre part from the \ laser crosshairs, leaving a gap in the middle, and \ return from the subroutine using a tail call