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⌂ ∞ Revs on the BBC Micro

Dashboard: fillDataOffset

       Name: fillDataOffset                                          [Show more]
       Type: Variable
   Category: Dashboard
    Summary: Dash data offsets, tweaked to give bottom line values that are
             compatible with the process of filling blocks to the left
  Deep dive: Creating objects from edges

    Context: See this variable in context in the source code
 References: This variable is used as follows:
             * FillInsideObject uses fillDataOffset




 Contains dash data offsets that are skewed so that dash data blocks whose left
 neighbours start lower down the screen than they do (i.e. they have a smaller
 offset) contain the left neighbour's offset rather than their own.

 This ensures that when filling blocks to the left of the current block, the
 value of the bottom line (i.e. the offset) is set to the bottom of the column
 being filled, rather than the smaller column to its right.



.fillDataOffset

 EQUB dashData0  - (dashData + &80 *  0) - 1    \ These match dashDataOffset
 EQUB dashData1  - (dashData + &80 *  1) - 1
 EQUB dashData2  - (dashData + &80 *  2) - 1
 EQUB dashData3  - (dashData + &80 *  3) - 1
 EQUB dashData4  - (dashData + &80 *  4) - 1
 EQUB dashData5  - (dashData + &80 *  5) - 1
 EQUB dashData6  - (dashData + &80 *  6) - 1

 EQUB dashData6  - (dashData + &80 *  6) - 1    \ dashData6 repeated, as block 7
                                                \ is smaller than block 6

 EQUB dashData7  - (dashData + &80 *  7) - 1    \ These are out by one, so the
 EQUB dashData8  - (dashData + &80 *  8) - 1    \ X-th entry is the offset for
 EQUB dashData9  - (dashData + &80 *  9) - 1    \ block X - 1
 EQUB dashData10 - (dashData + &80 * 10) - 1
 EQUB dashData11 - (dashData + &80 * 11) - 1
 EQUB dashData12 - (dashData + &80 * 12) - 1
 EQUB dashData13 - (dashData + &80 * 13) - 1
 EQUB dashData14 - (dashData + &80 * 14) - 1
 EQUB dashData15 - (dashData + &80 * 15) - 1
 EQUB dashData16 - (dashData + &80 * 16) - 1
 EQUB dashData17 - (dashData + &80 * 17) - 1
 EQUB dashData18 - (dashData + &80 * 18) - 1
 EQUB dashData19 - (dashData + &80 * 19) - 1
 EQUB dashData20 - (dashData + &80 * 20) - 1
 EQUB dashData21 - (dashData + &80 * 21) - 1
 EQUB dashData22 - (dashData + &80 * 22) - 1
 EQUB dashData23 - (dashData + &80 * 23) - 1
 EQUB dashData24 - (dashData + &80 * 24) - 1

                                                \ dashData25 skipped as block 26
                                                \ is larger than block 25

 EQUB dashData26 - (dashData + &80 * 26) - 1    \ These match dashDataOffset
 EQUB dashData27 - (dashData + &80 * 27) - 1
 EQUB dashData28 - (dashData + &80 * 28) - 1
 EQUB dashData29 - (dashData + &80 * 29) - 1
 EQUB dashData30 - (dashData + &80 * 30) - 1
 EQUB dashData31 - (dashData + &80 * 31) - 1
 EQUB dashData32 - (dashData + &80 * 32) - 1
 EQUB dashData33 - (dashData + &80 * 33) - 1
 EQUB dashData34 - (dashData + &80 * 34) - 1

 EQUB dashData34 - (dashData + &80 * 34) - 1    \ dashData34 repeated, as block
                                                \ 35 is smaller than block 34

 EQUB dashData35 - (dashData + &80 * 35) - 1    \ These are out by one, so the
 EQUB dashData36 - (dashData + &80 * 36) - 1    \ X-th entry is the offset for
                                                \ block X - 1

                                                \ dashData37 skipped as block 38
                                                \ is larger than block 37

 EQUB dashData38 - (dashData + &80 * 38) - 1    \ These match dashDataOffset
 EQUB dashData39 - (dashData + &80 * 39) - 1

 EQUB dashData40 - (dashData + &80 * 40) - 1    \ Not used for the screen buffer

 EQUB &20, &20          \ These bytes appear to be unused
 EQUB &20, &42
 EQUB &65, &68
 EQUB &69