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1.1 root 1: /*
2: Hatari
3:
4: Handle storing of writes to ST palette using clock-cycle counts. We can use this to accurately any form
5: of Spectrum512 style images - even down to the way the screen colours change on decompression routines in menus!
6:
7: As the 68000 has a 4-clock cycle increment we can only change palette every 4 cycles. This means that on one
8: scanline(512 cycles) we have just 512/4=128 places where palette writes can take place. We keep track of
9: this in a table(storing on each scanline and colour writes and the cycles on the scanline where they happen).
10: When we draw the screen we simply keep a cycle-count on the line and check this with our table and update
11: the 16-colour palette with each change. As the table is already ordered this makes things very simple. Speed
12: is a problem, though, as the palette can change once every 4 pixels - that's a lot of processing.
13: */
14:
1.1.1.4 ! root 15: #include <SDL_byteorder.h>
! 16:
1.1 root 17: #include "main.h"
18: #include "debug.h"
19: #include "decode.h"
20: #include "int.h"
21: #include "screen.h"
22: #include "spec512.h"
23: #include "video.h"
24:
1.1.1.2 root 25:
26: CYCLEPALETTE CyclePalettes[(SCANLINES_PER_FRAME+1)*MAX_CYCLEPALETTES_PERLINE]; /* 314k; 1024-bytes per line */
1.1 root 27: CYCLEPALETTE *pCyclePalette;
1.1.1.2 root 28: int nCyclePalettes[(SCANLINES_PER_FRAME+1)]; /* Number of entries in above table for each scanline */
29: int nPalettesAccess[(SCANLINES_PER_FRAME+1)]; /* Number of times accessed palette register 'x' in this scan line */
1.1 root 30: unsigned short int CycleColour;
31: int CycleColourIndex;
32: int nScanLine, ScanLineCycleCount;
33: BOOL bIsSpec512Display;
34:
1.1.1.4 ! root 35: #if SDL_BYTEORDER == SDL_BIG_ENDIAN
! 36: static const int STRGBPalEndianTable[16] = {0,2,1,3,8,10,9,11,4,6,5,7,12,14,13,15};
! 37: #endif
! 38:
1.1.1.2 root 39:
40: /*-----------------------------------------------------------------------*/
1.1 root 41: /*
42: Return TRUE if this frame is a Spectrum 512 style image(MUST be low res/non-mix)
43: */
44: BOOL Spec512_IsImage(void)
45: {
1.1.1.2 root 46: /* Normal Low res screen? */
1.1 root 47: if ( (STRes==ST_LOW_RES) && (bIsSpec512Display) )
48: return(TRUE);
49:
50: return(FALSE);
51: }
52:
1.1.1.2 root 53:
54: /*-----------------------------------------------------------------------*/
1.1 root 55: /*
56: We store every palette access in a table to perform Spectrum 512 colour effects
57: This is cleared on each VBL
58: */
59: void Spec512_StartVBL(void)
60: {
1.1.1.2 root 61: /* Clear number of cycle palettes on each frame */
1.1 root 62: memset(nCyclePalettes,0x0,(SCANLINES_PER_FRAME+1)*sizeof(int));
1.1.1.2 root 63: /* Clear number of times accessed on entry in palette (used to check if is true Spectrum 512 image) */
1.1 root 64: memset(nPalettesAccess,0x0,(SCANLINES_PER_FRAME+1)*sizeof(int));
1.1.1.2 root 65: /* Set as not Spectrum 512 displayed image */
1.1 root 66: bIsSpec512Display = FALSE;
67: }
68:
1.1.1.2 root 69:
70: /*-----------------------------------------------------------------------*/
1.1 root 71: /*
1.1.1.4 ! root 72: Store color into table 'CyclePalettes[]' for screen conversion according
! 73: to cycles into frame.
1.1 root 74: */
1.1.1.4 ! root 75: void Spec512_StoreCyclePalette(unsigned short col, unsigned long addr)
1.1 root 76: {
77: CYCLEPALETTE *pCyclePalette;
78: int FrameCycles,ScanLine;
79:
1.1.1.4 ! root 80: CycleColour = col;
! 81: CycleColourIndex = (addr-0xff8240)>>1;
! 82:
1.1.1.2 root 83: /* Find number of cycles into frame */
1.1 root 84: FrameCycles = Int_FindFrameCycles();
85:
1.1.1.2 root 86: /* Find scan line we are currently on and get index into cycle-palette table */
1.1 root 87: ScanLine = (FrameCycles/CYCLES_PER_LINE);
88: pCyclePalette = &CyclePalettes[ (ScanLine*MAX_CYCLEPALETTES_PERLINE) + nCyclePalettes[ScanLine] ];
1.1.1.2 root 89: /* Do we have a previous entry at the same cycles? If so, 68000 have used a 'move.l' instruction so stagger writes */
1.1 root 90: if (nCyclePalettes[ScanLine]>0) {
91: if ((pCyclePalette-1)->LineCycles==(FrameCycles&511))
1.1.1.2 root 92: FrameCycles += 4; /* Colours are staggered by [4,20] when writing a long word! */
1.1 root 93: }
94:
1.1.1.2 root 95: /* Store palette access */
96: pCyclePalette->LineCycles = FrameCycles&511; /* Cycles into scanline */
97: pCyclePalette->Colour = CycleColour&0x777; /* Store ST colour RGB */
98: pCyclePalette->Index = CycleColourIndex; /* And Index (0...15) */
99: /* Increment count(this can never overflow as you cannot write to the palette more than 'MAX_CYCLEPALETTES_PERLINE' times per scanline) */
1.1 root 100: nCyclePalettes[ScanLine]++;
101:
1.1.1.2 root 102: /* Check if program wrote to certain palette entry multiple times on a single scan-line */
103: /* If we did then we must be using a Spectrum512 image or some kind of colour cycling... */
1.1 root 104: nPalettesAccess[ScanLine]++;
105: if (nPalettesAccess[ScanLine]>=32)
106: bIsSpec512Display = TRUE;
107: }
108:
1.1.1.2 root 109:
110: /*-----------------------------------------------------------------------*/
1.1 root 111: /*
112: Begin palette calculation for Spectrum 512 style images,
113: */
114: void Spec512_StartFrame(void)
115: {
116: int i;
117:
1.1.1.2 root 118: /* Set so screen gets full-update when returns from Spectrum 512 display */
1.1 root 119: Screen_SetFullUpdate();
120:
1.1.1.2 root 121: /* Set terminators on each line, so when scan during conversion we know when to stop */
1.1.1.4 ! root 122: for(i=0; i<(SCANLINES_PER_FRAME+1); i++)
! 123: {
1.1 root 124: pCyclePalette = &CyclePalettes[ (i*MAX_CYCLEPALETTES_PERLINE) + nCyclePalettes[i] ];
1.1.1.2 root 125: pCyclePalette->LineCycles = -1; /* Term */
1.1 root 126: }
127:
1.1.1.2 root 128: /* Copy first line palette, kept in 'HBLPalettes' and store to 'STRGBPalette' */
1.1 root 129: for(i=0; i<16; i++)
1.1.1.4 ! root 130: {
! 131: #if SDL_BYTEORDER == SDL_BIG_ENDIAN
! 132: STRGBPalette[STRGBPalEndianTable[i]] = ST2RGB[HBLPalettes[i]&0x777];
! 133: #else
1.1 root 134: STRGBPalette[i] = ST2RGB[HBLPalettes[i]&0x777];
1.1.1.4 ! root 135: #endif
! 136: }
1.1 root 137:
1.1.1.2 root 138: /* Ready for first call to 'Spec512_ScanLine' */
1.1 root 139: nScanLine = 0;
140:
1.1.1.2 root 141: /* Skip to first line(where start to draw screen from) */
1.1 root 142: for (i=0; i<(STScreenStartHorizLine+(nStartHBL-OVERSCAN_TOP)); i++)
143: Spec512_ScanWholeLine();
144: }
145:
1.1.1.2 root 146:
147: /*-----------------------------------------------------------------------*/
1.1 root 148: /*
149: Scan whole line and build up palette - need to do this so when get to screen line we have
150: the correct 16 colours set
151: */
152: void Spec512_ScanWholeLine(void)
153: {
1.1.1.2 root 154: /* Store pointer to line of palette cycle writes */
1.1 root 155: pCyclePalette = &CyclePalettes[nScanLine*MAX_CYCLEPALETTES_PERLINE];
1.1.1.2 root 156: /* Ready for next scan line */
1.1 root 157: nScanLine++;
158:
1.1.1.2 root 159: /* Update palette entries until we reach start of displayed screen */
1.1 root 160: ScanLineCycleCount = 0;
1.1.1.2 root 161: Spec512_EndScanLine(); /* Read whole line of palettes and update 'STRGBPalette' */
1.1 root 162: }
163:
1.1.1.2 root 164:
165: /*-----------------------------------------------------------------------*/
1.1 root 166: /*
167: Build up palette for this scan line and store in 'ScanLinePalettes'
168: */
169: void Spec512_StartScanLine(void)
170: {
171: int i;
172:
1.1.1.2 root 173: /* Store pointer to line of palette cycle writes */
1.1 root 174: pCyclePalette = &CyclePalettes[nScanLine*MAX_CYCLEPALETTES_PERLINE];
1.1.1.2 root 175: /* Ready for next scan line */
1.1 root 176: nScanLine++;
177:
1.1.1.2 root 178: /* Update palette entries until we reach start of displayed screen */
1.1 root 179: ScanLineCycleCount = 0;
1.1.1.2 root 180: for(i=0; i<((SCREEN_START_CYCLE-8)/4); i++) /* This '8' is as we've already added in the 'move' instruction timing */
181: Spec512_UpdatePaletteSpan(); /* Update palette for this 4-cycle period */
182: /* And skip for left border is not using overscan display to user */
183: for (i=0; i<(STScreenLeftSkipBytes/2); i++) /* Eg, 16 bytes = 32 pixels or 8 palette periods */
1.1 root 184: Spec512_UpdatePaletteSpan();
185: }
186:
1.1.1.2 root 187:
188: /*-----------------------------------------------------------------------*/
1.1 root 189: /*
190: Run to end of scan line looking up palettes so 'STRGBPalette' is up-to-date
191: */
192: void Spec512_EndScanLine(void)
193: {
1.1.1.2 root 194: /* Continue to reads palette until complete so have correct version for next line */
1.1 root 195: while(ScanLineCycleCount<CYCLES_PER_LINE)
196: Spec512_UpdatePaletteSpan();
197: }
198:
1.1.1.2 root 199:
200: /*-----------------------------------------------------------------------*/
1.1 root 201: /*
202: Update palette for 4-pixels span, storing to 'STRGBPalette'
203: */
204: void Spec512_UpdatePaletteSpan(void)
205: {
1.1.1.2 root 206: if( pCyclePalette->LineCycles == ScanLineCycleCount )
207: {
208: /* Need to update palette with new entry */
1.1.1.4 ! root 209: #if SDL_BYTEORDER == SDL_BIG_ENDIAN
! 210: STRGBPalette[STRGBPalEndianTable[pCyclePalette->Index]] = ST2RGB[pCyclePalette->Colour&0x777];
! 211: #else
1.1.1.2 root 212: STRGBPalette[pCyclePalette->Index] = ST2RGB[pCyclePalette->Colour&0x777];
1.1.1.4 ! root 213: #endif
1.1.1.2 root 214: pCyclePalette += 1;
215: }
216: ScanLineCycleCount += 4; /* Next 4 cycles */
1.1 root 217: }
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