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Elite on the BBC Micro

Flight: SIGHT [Disc version, Docked]

Name: SIGHT [Show more] Type: Subroutine Category: Flight Summary: Draw the laser crosshairs
Context: See this subroutine in context in the source code Variations: See code variations for this subroutine in the different versions References: No direct references to this subroutine in this source file
.SIGHT LDY VIEW \ Fetch the laser power for our new view LDA LASER,Y BEQ BOL1-1 \ If it is zero (i.e. there is no laser fitted to this \ view), jump to BOL1-1 to return from the subroutine \ (as BOL1-1 contains &60, which is the opcode for an \ RTS) 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 TT15 \ Call TT15 to draw crosshairs of size 20 just to the \ left of the middle of the screen LDA #10 \ Set QQ19+2 to size 10 for the crosshairs size STA QQ19+2 JMP TT15 \ Call TT15 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