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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 "int.h"
20: #include "screen.h"
21: #include "spec512.h"
22: #include "video.h"
23:
1.1.1.2 root 24:
25: CYCLEPALETTE CyclePalettes[(SCANLINES_PER_FRAME+1)*MAX_CYCLEPALETTES_PERLINE]; /* 314k; 1024-bytes per line */
1.1 root 26: CYCLEPALETTE *pCyclePalette;
1.1.1.2 root 27: int nCyclePalettes[(SCANLINES_PER_FRAME+1)]; /* Number of entries in above table for each scanline */
28: int nPalettesAccess[(SCANLINES_PER_FRAME+1)]; /* Number of times accessed palette register 'x' in this scan line */
1.1 root 29: unsigned short int CycleColour;
30: int CycleColourIndex;
31: int nScanLine, ScanLineCycleCount;
32: BOOL bIsSpec512Display;
1.1.1.5 root 33: int nb_spc512lines,last_spc512line;
1.1 root 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) */
1.1.1.5 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;
1.1.1.5 root 67: last_spc512line = -1;
68: nb_spc512lines = 0;
1.1 root 69: }
70:
1.1.1.2 root 71:
72: /*-----------------------------------------------------------------------*/
1.1 root 73: /*
1.1.1.4 root 74: Store color into table 'CyclePalettes[]' for screen conversion according
75: to cycles into frame.
1.1 root 76: */
1.1.1.4 root 77: void Spec512_StoreCyclePalette(unsigned short col, unsigned long addr)
1.1 root 78: {
79: CYCLEPALETTE *pCyclePalette;
80: int FrameCycles,ScanLine;
81:
1.1.1.4 root 82: CycleColour = col;
83: CycleColourIndex = (addr-0xff8240)>>1;
84:
1.1.1.2 root 85: /* Find number of cycles into frame */
1.1 root 86: FrameCycles = Int_FindFrameCycles();
87:
1.1.1.2 root 88: /* Find scan line we are currently on and get index into cycle-palette table */
1.1 root 89: ScanLine = (FrameCycles/CYCLES_PER_LINE);
90: pCyclePalette = &CyclePalettes[ (ScanLine*MAX_CYCLEPALETTES_PERLINE) + nCyclePalettes[ScanLine] ];
1.1.1.2 root 91: /* 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 92: if (nCyclePalettes[ScanLine]>0) {
93: if ((pCyclePalette-1)->LineCycles==(FrameCycles&511))
1.1.1.2 root 94: FrameCycles += 4; /* Colours are staggered by [4,20] when writing a long word! */
1.1 root 95: }
96:
1.1.1.2 root 97: /* Store palette access */
98: pCyclePalette->LineCycles = FrameCycles&511; /* Cycles into scanline */
99: pCyclePalette->Colour = CycleColour&0x777; /* Store ST colour RGB */
100: pCyclePalette->Index = CycleColourIndex; /* And Index (0...15) */
101: /* Increment count(this can never overflow as you cannot write to the palette more than 'MAX_CYCLEPALETTES_PERLINE' times per scanline) */
1.1 root 102: nCyclePalettes[ScanLine]++;
103:
1.1.1.2 root 104: /* Check if program wrote to certain palette entry multiple times on a single scan-line */
105: /* If we did then we must be using a Spectrum512 image or some kind of colour cycling... */
1.1 root 106: nPalettesAccess[ScanLine]++;
1.1.1.5 root 107: if (nPalettesAccess[ScanLine]>=32) {
108: /* This code has obviously something wrong. It detects the grav44 disk
109: demo as a spc512 image because the scroller at the bottom of the screen
110: uses more than 1 palette... But doing so, it ruins the colours of the
111: rest of the screen. I should review all this code, but later.
112: For now, I just make sure it chosses this mode only when most of the
113: screen is a spc512 screen (at least 150 lines ! */
114: if (last_spc512line != ScanLine) {
115: last_spc512line = ScanLine;
116: nb_spc512lines++;
117: if (nb_spc512lines >= 150)
118: bIsSpec512Display = TRUE;
119: }
120: }
1.1 root 121: }
122:
1.1.1.2 root 123:
124: /*-----------------------------------------------------------------------*/
1.1 root 125: /*
1.1.1.5 root 126: Begin palette calculation for Spectrum 512 style images,
1.1 root 127: */
128: void Spec512_StartFrame(void)
129: {
130: int i;
131:
1.1.1.2 root 132: /* Set so screen gets full-update when returns from Spectrum 512 display */
1.1 root 133: Screen_SetFullUpdate();
134:
1.1.1.2 root 135: /* Set terminators on each line, so when scan during conversion we know when to stop */
1.1.1.4 root 136: for(i=0; i<(SCANLINES_PER_FRAME+1); i++)
137: {
1.1 root 138: pCyclePalette = &CyclePalettes[ (i*MAX_CYCLEPALETTES_PERLINE) + nCyclePalettes[i] ];
1.1.1.2 root 139: pCyclePalette->LineCycles = -1; /* Term */
1.1 root 140: }
141:
1.1.1.2 root 142: /* Copy first line palette, kept in 'HBLPalettes' and store to 'STRGBPalette' */
1.1 root 143: for(i=0; i<16; i++)
1.1.1.4 root 144: {
145: #if SDL_BYTEORDER == SDL_BIG_ENDIAN
1.1.1.5 root 146: STRGBPalette[STRGBPalEndianTable[i]] = ST2RGB[pHBLPalettes[i]&0x777];
1.1.1.4 root 147: #else
1.1.1.5 root 148: STRGBPalette[i] = ST2RGB[pHBLPalettes[i]&0x777];
1.1.1.4 root 149: #endif
150: }
1.1 root 151:
1.1.1.2 root 152: /* Ready for first call to 'Spec512_ScanLine' */
1.1 root 153: nScanLine = 0;
1.1.1.5 root 154: if (OverscanMode & OVERSCANMODE_TOP)
155: nScanLine += OVERSCAN_TOP;
1.1 root 156:
1.1.1.2 root 157: /* Skip to first line(where start to draw screen from) */
1.1 root 158: for (i=0; i<(STScreenStartHorizLine+(nStartHBL-OVERSCAN_TOP)); i++)
159: Spec512_ScanWholeLine();
160: }
161:
1.1.1.2 root 162:
163: /*-----------------------------------------------------------------------*/
1.1 root 164: /*
165: Scan whole line and build up palette - need to do this so when get to screen line we have
166: the correct 16 colours set
167: */
168: void Spec512_ScanWholeLine(void)
169: {
1.1.1.2 root 170: /* Store pointer to line of palette cycle writes */
1.1 root 171: pCyclePalette = &CyclePalettes[nScanLine*MAX_CYCLEPALETTES_PERLINE];
1.1.1.2 root 172: /* Ready for next scan line */
1.1 root 173: nScanLine++;
174:
1.1.1.2 root 175: /* Update palette entries until we reach start of displayed screen */
1.1 root 176: ScanLineCycleCount = 0;
1.1.1.2 root 177: Spec512_EndScanLine(); /* Read whole line of palettes and update 'STRGBPalette' */
1.1 root 178: }
179:
1.1.1.2 root 180:
181: /*-----------------------------------------------------------------------*/
1.1 root 182: /*
183: Build up palette for this scan line and store in 'ScanLinePalettes'
184: */
185: void Spec512_StartScanLine(void)
186: {
187: int i;
188:
1.1.1.2 root 189: /* Store pointer to line of palette cycle writes */
1.1 root 190: pCyclePalette = &CyclePalettes[nScanLine*MAX_CYCLEPALETTES_PERLINE];
1.1.1.2 root 191: /* Ready for next scan line */
1.1 root 192: nScanLine++;
193:
1.1.1.2 root 194: /* Update palette entries until we reach start of displayed screen */
1.1 root 195: ScanLineCycleCount = 0;
1.1.1.2 root 196: for(i=0; i<((SCREEN_START_CYCLE-8)/4); i++) /* This '8' is as we've already added in the 'move' instruction timing */
197: Spec512_UpdatePaletteSpan(); /* Update palette for this 4-cycle period */
198: /* And skip for left border is not using overscan display to user */
199: for (i=0; i<(STScreenLeftSkipBytes/2); i++) /* Eg, 16 bytes = 32 pixels or 8 palette periods */
1.1 root 200: Spec512_UpdatePaletteSpan();
201: }
202:
1.1.1.2 root 203:
204: /*-----------------------------------------------------------------------*/
1.1 root 205: /*
206: Run to end of scan line looking up palettes so 'STRGBPalette' is up-to-date
207: */
208: void Spec512_EndScanLine(void)
209: {
1.1.1.2 root 210: /* Continue to reads palette until complete so have correct version for next line */
1.1 root 211: while(ScanLineCycleCount<CYCLES_PER_LINE)
212: Spec512_UpdatePaletteSpan();
213: }
214:
1.1.1.2 root 215:
216: /*-----------------------------------------------------------------------*/
1.1 root 217: /*
218: Update palette for 4-pixels span, storing to 'STRGBPalette'
219: */
220: void Spec512_UpdatePaletteSpan(void)
221: {
1.1.1.2 root 222: if( pCyclePalette->LineCycles == ScanLineCycleCount )
223: {
224: /* Need to update palette with new entry */
1.1.1.4 root 225: #if SDL_BYTEORDER == SDL_BIG_ENDIAN
226: STRGBPalette[STRGBPalEndianTable[pCyclePalette->Index]] = ST2RGB[pCyclePalette->Colour&0x777];
227: #else
1.1.1.2 root 228: STRGBPalette[pCyclePalette->Index] = ST2RGB[pCyclePalette->Colour&0x777];
1.1.1.4 root 229: #endif
1.1.1.2 root 230: pCyclePalette += 1;
231: }
232: ScanLineCycleCount += 4; /* Next 4 cycles */
1.1 root 233: }
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