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Display @ symbols on startup
There's actually a lot going on here to make the @ symbol display happen. The @ symbols are the visual representation of NUL-character bytes. They are inverse video, as dictated by the Apple //e technical reference. As part of the bootup sequence, those bytes are overwritten with space characters. As part of the work, we now have a table of rows and columns that map to display buffer addresses.
This commit is contained in:
Peter Evans
parent
1a6d8b6ced
commit
7edf0c5dbd
@ -99,10 +99,6 @@ apple2_draw_40col(apple2 *mach)
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vm_screen_prepare(mach->screen);
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for (addr = 0x400; addr < 0x800; addr++) {
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if ((addr & 0xFF) == 0x39) {
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addr += 0x40;
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}
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apple2_text_draw(mach, addr);
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}
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}
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@ -14,6 +14,151 @@
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#include "apple2.text.h"
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/*
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* This table maps display buffer addresses for 40-column text to the
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* corresponding row on-screen (given a 40x24 grid). A negative column
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* indicates that the address is not displayable.
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*/
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static int buffer_rows[] = {
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// 0 1 2 3 4 5 6 7 8 9 A B C D E F
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // $400
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // $410
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0, 0, 0, 0, 0, 0, 0, 0, 8, 8, 8, 8, 8, 8, 8, 8, // $420
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8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, // $430
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8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, // $440
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16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, // $450
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16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, // $460
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16, 16, 16, 16, 16, 16, 16, 16, -1, -1, -1, -1, -1, -1, -1, -1, // $470
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // $480
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // $490
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1, 1, 1, 1, 1, 1, 1, 1, 9, 9, 9, 9, 9, 9, 9, 9, // $4A0
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9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, // $4B0
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9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, // $4C0
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17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, // $4D0
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17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, // $4E0
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17, 17, 17, 17, 17, 17, 17, 17, -1, -1, -1, -1, -1, -1, -1, -1, // $4F0
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2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, // $500
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2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, // $510
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2, 2, 2, 2, 2, 2, 2, 2, 10, 10, 10, 10, 10, 10, 10, 10, // $520
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10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, // $530
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10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, // $540
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18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, // $550
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18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, // $560
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18, 18, 18, 18, 18, 18, 18, 18, -1, -1, -1, -1, -1, -1, -1, -1, // $570
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3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, // $580
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3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, // $590
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3, 3, 3, 3, 3, 3, 3, 3, 11, 11, 11, 11, 11, 11, 11, 11, // $5A0
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11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, // $5B0
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11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, // $5C0
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19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, // $5D0
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19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, // $5E0
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19, 19, 19, 19, 19, 19, 19, 19, -1, -1, -1, -1, -1, -1, -1, -1, // $5F0
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4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, // $600
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4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, // $610
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4, 4, 4, 4, 4, 4, 4, 4, 12, 12, 12, 12, 12, 12, 12, 12, // $620
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12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, // $630
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12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, // $640
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20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, // $650
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20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, // $660
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20, 20, 20, 20, 20, 20, 20, 20, -1, -1, -1, -1, -1, -1, -1, -1, // $670
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5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, // $680
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5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, // $690
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5, 5, 5, 5, 5, 5, 5, 5, 13, 13, 13, 13, 13, 13, 13, 13, // $6A0
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13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, // $6B0
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13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, // $6C0
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21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, // $6D0
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21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, // $6E0
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21, 21, 21, 21, 21, 21, 21, 21, -1, -1, -1, -1, -1, -1, -1, -1, // $6F0
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6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, // $700
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6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, // $710
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6, 6, 6, 6, 6, 6, 6, 6, 14, 14, 14, 14, 14, 14, 14, 14, // $720
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14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, // $730
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14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, // $740
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22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, // $750
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22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, // $760
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22, 22, 22, 22, 22, 22, 22, 22, -1, -1, -1, -1, -1, -1, -1, -1, // $770
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7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, // $780
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7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, // $790
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7, 7, 7, 7, 7, 7, 7, 7, 15, 15, 15, 15, 15, 15, 15, 15, // $7A0
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15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, // $7B0
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15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, // $7C0
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23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, // $7D0
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23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, // $7E0
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23, 23, 23, 23, 23, 23, 23, 23, -1, -1, -1, -1, -1, -1, -1, -1, // $7F0
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};
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/*
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* Similar to buffer_rows, this table defines the column numbers for
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* buffer display addresses.
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*/
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static int buffer_cols[] = {
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// 0 1 2 3 4 5 6 7 8 9 A B C D E F
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, // $400
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16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, // $410
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32, 33, 34, 35, 36, 37, 38, 39, 0, 1, 2, 3, 4, 5, 6, 7, // $420
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8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, // $430
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24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, // $440
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, // $450
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16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, // $460
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32, 33, 34, 35, 36, 37, 38, 39, -1, -1, -1, -1, -1, -1, -1, -1, // $470
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, // $480
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16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, // $490
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32, 33, 34, 35, 36, 37, 38, 39, 0, 1, 2, 3, 4, 5, 6, 7, // $4A0
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8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, // $4B0
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24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, // $4C0
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, // $4D0
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16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, // $4E0
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32, 33, 34, 35, 36, 37, 38, 39, -1, -1, -1, -1, -1, -1, -1, -1, // $4F0
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, // $500
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16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, // $510
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32, 33, 34, 35, 36, 37, 38, 39, 0, 1, 2, 3, 4, 5, 6, 7, // $520
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8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, // $530
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24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, // $540
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, // $550
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16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, // $560
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32, 33, 34, 35, 36, 37, 38, 39, -1, -1, -1, -1, -1, -1, -1, -1, // $570
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, // $580
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16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, // $590
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32, 33, 34, 35, 36, 37, 38, 39, 0, 1, 2, 3, 4, 5, 6, 7, // $5A0
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8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, // $5B0
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24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, // $5C0
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, // $5D0
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16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, // $5E0
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32, 33, 34, 35, 36, 37, 38, 39, -1, -1, -1, -1, -1, -1, -1, -1, // $5F0
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, // $600
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16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, // $610
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32, 33, 34, 35, 36, 37, 38, 39, 0, 1, 2, 3, 4, 5, 6, 7, // $620
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8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, // $630
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24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, // $640
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, // $650
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16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, // $660
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32, 33, 34, 35, 36, 37, 38, 39, -1, -1, -1, -1, -1, -1, -1, -1, // $670
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, // $680
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16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, // $690
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32, 33, 34, 35, 36, 37, 38, 39, 0, 1, 2, 3, 4, 5, 6, 7, // $6A0
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8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, // $6B0
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24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, // $6C0
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, // $6D0
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16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, // $6E0
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32, 33, 34, 35, 36, 37, 38, 39, -1, -1, -1, -1, -1, -1, -1, -1, // $6F0
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, // $700
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16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, // $710
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32, 33, 34, 35, 36, 37, 38, 39, 0, 1, 2, 3, 4, 5, 6, 7, // $720
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8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, // $730
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24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, // $740
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, // $750
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16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, // $760
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32, 33, 34, 35, 36, 37, 38, 39, -1, -1, -1, -1, -1, -1, -1, -1, // $770
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, // $780
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16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, // $790
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32, 33, 34, 35, 36, 37, 38, 39, 0, 1, 2, 3, 4, 5, 6, 7, // $7A0
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8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, // $7B0
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24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, // $7C0
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, // $7D0
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16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, // $7E0
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32, 33, 34, 35, 36, 37, 38, 39, -1, -1, -1, -1, -1, -1, -1, -1, // $7F0
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};
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/*
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* This is the primary character set of display symbols. The order of
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* characters generally follows ASCII order, but doesn't map to ASCII
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@ -98,7 +243,7 @@ apple2_text_alternate(char ch)
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void
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apple2_text_draw(apple2 *mach, size_t addr)
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{
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int err;
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int err, row;
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bool inverse, flashing;
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vm_8bit ch;
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vm_area dest;
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@ -117,6 +262,12 @@ apple2_text_draw(apple2 *mach, size_t addr)
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// Default
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font = mach->sysfont;
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// This is actually not a byte that is displayable, so let's get out
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row = buffer_rows[addr - 0x400];
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if (row == -1) {
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return;
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}
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err = apple2_text_area(&dest, font, addr);
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if (err != OK) {
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return;
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@ -158,9 +309,6 @@ apple2_text_draw(apple2 *mach, size_t addr)
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int
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apple2_text_area(vm_area *area, vm_bitfont *font, size_t addr)
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{
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vm_8bit lsb;
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int page_base;
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// The text display buffers are located at "Page 1" and "Page 2",
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// which are at byte 1024-2047 (0x0400-0x07FF) and byte 2048-3071
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// (0x0800-0x0BFF) respectively. If the given address is not in
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@ -175,37 +323,17 @@ apple2_text_area(vm_area *area, vm_bitfont *font, size_t addr)
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// address indicates the place on the grid where text should go. We
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// don't care how it got there. Let's figure out that position
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// on-screen.
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lsb = addr & 0xff; // column
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// Regardless of which page we're rendering into, we can only use 40
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// cells on the grid (that is, 0-39 from whatever value the msb is).
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// It's possible to have an lsb greater than that, but if so, it's
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// not anything we can render to the screen.
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if (lsb > 0x39) {
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return 0;
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}
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if ((addr & 0xff80) % 128 != 0) {
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return 0;
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}
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// By default, we assume we're in text page 1. If the address ends
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// up being greater than 0x07FF, then we must be in page 2.
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page_base = 0x0400;
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if (addr > 0x07FF) {
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page_base = 0x0800;
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}
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// The absolute column position will be the font width times the
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// lsb.
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area->xoff = lsb * font->width;
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area->xoff = buffer_cols[addr - 0x400] * font->width;
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// The absolute row position will be the font height times the msb
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// minus the page base (because the height is the same regardless of
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// what page we're in). So if we're msb $0400, then we're starting
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// on pixel row 0; but if we're msb $0480, then we are starting on
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// pixel row 8 (where the font height is 8); etc.
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area->yoff = ((addr & 0xff80) - page_base) * font->height;
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area->yoff = buffer_rows[addr - 0x400] * font->height;
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// Our width and height must be that of the font.
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area->width = font->width;
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