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Elite on the BBC Micro

Drawing pixels: CPIX2 [Elite-A, Parasite]

Name: CPIX2 [Show more] Type: Subroutine Category: Drawing pixels Summary: Draw a single-height dash on the dashboard by sending a draw_blob command to the I/O processor
Context: See this subroutine in context in the source code References: This subroutine is called as follows: * CPIX4 calls CPIX2 * DOT calls CPIX2

Arguments: X1 The screen pixel x-coordinate of the dash Y1 The screen pixel y-coordinate of the dash COL The colour of the dash as a mode 5 character row byte
.CPIX2 LDA #&90 \ Send command &90 to the I/O processor: JSR tube_write \ \ draw_blob(x, y, colour) \ \ which will draw a dash of the specified colour and \ position on the dashboard LDA X1 \ Send the first parameter to the I/O processor: JSR tube_write \ \ * x = X1 LDA Y1 \ Send the second parameter to the I/O processor: JSR tube_write \ \ * y = Y1 LDA COL \ Send the third parameter to the I/O processor: JMP tube_write \ \ * colour = COL \ \ and return from the subroutine using a tail call