all repos — mgba @ 61a4cc5d230bef3da151ef04c824558d8345b710

mGBA Game Boy Advance Emulator

src/ds/gx/software.c (view raw)

  1/* Copyright (c) 2013-2017 Jeffrey Pfau
  2 *
  3 * This Source Code Form is subject to the terms of the Mozilla Public
  4 * License, v. 2.0. If a copy of the MPL was not distributed with this
  5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
  6#include <mgba/internal/ds/gx/software.h>
  7
  8#include <mgba-util/memory.h>
  9#include "gba/renderers/software-private.h"
 10
 11#define SCREEN_SIZE (DS_VIDEO_VERTICAL_PIXELS << 12)
 12
 13DEFINE_VECTOR(DSGXSoftwarePolygonList, struct DSGXSoftwarePolygon);
 14DEFINE_VECTOR(DSGXSoftwareEdgeList, struct DSGXSoftwareEdge);
 15DEFINE_VECTOR(DSGXSoftwareSpanList, struct DSGXSoftwareSpan);
 16
 17static void DSGXSoftwareRendererInit(struct DSGXRenderer* renderer);
 18static void DSGXSoftwareRendererReset(struct DSGXRenderer* renderer);
 19static void DSGXSoftwareRendererDeinit(struct DSGXRenderer* renderer);
 20static void DSGXSoftwareRendererInvalidateTex(struct DSGXRenderer* renderer, int slot);
 21static void DSGXSoftwareRendererSetRAM(struct DSGXRenderer* renderer, struct DSGXVertex* verts, struct DSGXPolygon* polys, unsigned polyCount);
 22static void DSGXSoftwareRendererDrawScanline(struct DSGXRenderer* renderer, int y);
 23static void DSGXSoftwareRendererGetScanline(struct DSGXRenderer* renderer, int y, color_t** output);
 24
 25static void _expandColor(uint16_t c15, uint8_t* r, uint8_t* g, uint8_t* b) {
 26	*r = ((c15 << 1) & 0x3E) | 1;
 27	*g = ((c15 >> 4) & 0x3E) | 1;
 28	*b = ((c15 >> 9) & 0x3E) | 1;
 29}
 30
 31static color_t _finishColor(uint8_t r, uint8_t g, uint8_t b) {
 32#ifndef COLOR_16_BIT
 33	color_t rgb = (r << 2) & 0xF8;
 34	rgb |= (g << 10) & 0xF800;
 35	rgb |= (b << 18) & 0xF80000;
 36	return rgb;
 37#else
 38#error Unsupported color depth
 39#endif
 40}
 41
 42static color_t _lookupColor(struct DSGXSoftwareEndpoint* ep, struct DSGXSoftwarePolygon* poly) {
 43	// TODO: Optimize
 44	uint16_t texel;
 45
 46	int16_t s = ep->s >> 4;
 47	int16_t t = ep->t >> 4;
 48	if (!DSGXTexParamsIsSRepeat(poly->poly->texParams)) {
 49		if (s < 0) {
 50			s = 0;
 51		} else if (s >= poly->texW) {
 52			s = poly->texW - 1;
 53		}
 54	} else if (DSGXTexParamsIsSMirror(poly->poly->texParams)) {
 55		if (s & poly->texW) {
 56			s = poly->texW - s;
 57		}
 58		s &= poly->texW - 1;
 59	} else {
 60		s &= poly->texW - 1;
 61	}
 62	if (!DSGXTexParamsIsTRepeat(poly->poly->texParams)) {
 63		if (t < 0) {
 64			t = 0;
 65		} else if (t >= poly->texH) {
 66			t = poly->texW - 1;
 67		}
 68	} else if (DSGXTexParamsIsTMirror(poly->poly->texParams)) {
 69		if (t & poly->texH) {
 70			t = poly->texH - t;
 71		}
 72		t &= poly->texH - 1;
 73	} else {
 74		t &= poly->texH - 1;
 75	}
 76
 77	uint16_t texelCoord = s + t * poly->texW;
 78	switch (poly->texFormat) {
 79	case 0:
 80	default:
 81		return _finishColor(ep->cr, ep->cg, ep->cb);
 82	case 1:
 83		return _finishColor(0, 0, 0x3F);
 84	case 2:
 85		texel = ((uint8_t*) poly->texBase)[texelCoord >> 2];
 86		if (texelCoord & 0x3) {
 87			texel >>= 2 * texel & 3;
 88		}
 89		texel &= 0x3;
 90		break;
 91	case 3:
 92		texel = ((uint8_t*) poly->texBase)[texelCoord >> 1];
 93		if (texelCoord & 0x1) {
 94			texel >>= 4;
 95		}
 96		texel &= 0xF;
 97		break;
 98	case 4:
 99		texel = ((uint8_t*) poly->texBase)[texelCoord];
100		break;
101	case 5:
102		return _finishColor(0x3F, 0, 0x3F);
103	case 6:
104		return _finishColor(0x3F, 0x3F, 0);
105	case 7:
106		return _finishColor(0x3F, 0x3F, 0x3F);
107	}
108	if (DSGXTexParamsIs0Transparent(poly->poly->texParams) && !texel) {
109		return FLAG_UNWRITTEN;
110	}
111	uint8_t r, g, b;
112	texel = poly->palBase[texel];
113	_expandColor(texel, &r, &g, &b);
114	return _finishColor(r, g, b);
115}
116
117static int _edgeSort(const void* a, const void* b) {
118	const struct DSGXSoftwareEdge* ea = a;
119	const struct DSGXSoftwareEdge* eb = b;
120
121	// Sort upside down
122	if (ea->y0 < eb->y0) {
123		return 1;
124	}
125	if (ea->y0 > eb->y0) {
126		return -1;
127	}
128	if (ea->y1 < eb->y1) {
129		return 1;
130	}
131	if (ea->y1 > eb->y1) {
132		return -1;
133	}
134	return 0;
135}
136
137static bool _edgeToSpan(struct DSGXSoftwareSpan* span, const struct DSGXSoftwareEdge* edge, int index, int32_t y) {
138	int32_t height = edge->y1 - edge->y0;
139	int64_t yw = (y << 12) - edge->y0;
140	if (!height) {
141		return false;
142	}
143	// Clamp to bounds
144	if (yw < 0) {
145		yw = 0;
146	} else if (yw > height) {
147		yw = height;
148	}
149	int64_t heightRecip = 0x100000000LL / height;
150	span->ep[index].x = ((((int64_t) (edge->x1 - edge->x0) * yw) * heightRecip) >> 32) + edge->x0;
151	if (index && span->ep[0].x > span->ep[index].x) {
152		int32_t temp = span->ep[index].x;
153		span->ep[index] = span->ep[0];
154		span->ep[0].x = temp;
155		index = 0;
156	}
157	int32_t w = ((((int64_t) (edge->w1 - edge->w0) * yw) * heightRecip) >> 32) + edge->w0;
158	int64_t wRecip = 0x1000000000000LL / w;
159	span->ep[index].w = w;
160	span->ep[index].cr = ((((((int32_t) (edge->cr1 * edge->w1 - edge->cr0 * edge->w0) * yw) * heightRecip) >> 32) + edge->cr0 * edge->w0) * wRecip) >> 48;
161	span->ep[index].cg = ((((((int32_t) (edge->cg1 * edge->w1 - edge->cg0 * edge->w0) * yw) * heightRecip) >> 32) + edge->cg0 * edge->w0) * wRecip) >> 48;
162	span->ep[index].cb = ((((((int32_t) (edge->cb1 * edge->w1 - edge->cb0 * edge->w0) * yw) * heightRecip) >> 32) + edge->cb0 * edge->w0) * wRecip) >> 48;
163	span->ep[index].s = ((((((int32_t) (edge->s1 * edge->w1 - edge->s0 * edge->w0) * yw) * heightRecip) >> 32) + edge->s0 * edge->w0) * wRecip) >> 48;
164	span->ep[index].t = ((((((int32_t) (edge->t1 * edge->w1 - edge->t0 * edge->w0) * yw) * heightRecip) >> 32) + edge->t0 * edge->w0) * wRecip) >> 48;
165
166	return true;
167}
168
169static int _spanSort(const void* a, const void* b) {
170	const struct DSGXSoftwareSpan* sa = a;
171	const struct DSGXSoftwareSpan* sb = b;
172
173	// Sort backwards
174	if (sa->ep[0].x < sb->ep[0].x) {
175		return 1;
176	}
177	if (sa->ep[0].x > sb->ep[0].x) {
178		return -1;
179	}
180	if (sa->ep[0].w < sb->ep[0].w) {
181		return 1;
182	}
183	if (sa->ep[0].w > sb->ep[0].w) {
184		return -1;
185	}
186	return 0;
187}
188
189static void _lerpEndpoint(const struct DSGXSoftwareSpan* span, struct DSGXSoftwareEndpoint* ep, unsigned x) {
190	int64_t width = span->ep[1].x - span->ep[0].x;
191	int64_t xw = ((uint64_t) x << 12) - span->ep[0].x;
192	if (!width) {
193		return; // TODO?
194	}
195	// Clamp to bounds
196	if (xw < 0) {
197		xw = 0;
198	} else if (xw > width) {
199		xw = width;
200	}
201	int32_t w0 = span->ep[0].w;
202	int32_t w1 = span->ep[1].w;
203	int64_t widthRecip = 0x100000000LL / width;
204	int32_t w = ((((int64_t) (w1 - w0) * xw) * widthRecip) >> 32) + w0;
205	ep->w = w;
206	int64_t wRecip = 0x1000000000000LL / w;
207
208	uint64_t r = ((((span->ep[1].cr * (int64_t) w1 - span->ep[0].cr * (int64_t) w0) * xw) * widthRecip) >> 32) + span->ep[0].cr * (int64_t) w0;
209	uint64_t g = ((((span->ep[1].cg * (int64_t) w1 - span->ep[0].cg * (int64_t) w0) * xw) * widthRecip) >> 32) + span->ep[0].cg * (int64_t) w0;
210	uint64_t b = ((((span->ep[1].cb * (int64_t) w1 - span->ep[0].cb * (int64_t) w0) * xw) * widthRecip) >> 32) + span->ep[0].cb * (int64_t) w0;
211	ep->cr = (r * wRecip) >> 48;
212	ep->cg = (g * wRecip) >> 48;
213	ep->cb = (b * wRecip) >> 48;
214
215	int32_t s = ((((span->ep[1].s * (int64_t) w1 - span->ep[0].s * (int64_t) w0) * xw) * widthRecip) >> 32) + span->ep[0].s * (int64_t) w0;
216	int32_t t = ((((span->ep[1].t * (int64_t) w1 - span->ep[0].t * (int64_t) w0) * xw) * widthRecip) >> 32) + span->ep[0].t * (int64_t) w0;
217	ep->s = (s * wRecip) >> 48;
218	ep->t = (t * wRecip) >> 48;
219}
220
221void DSGXSoftwareRendererCreate(struct DSGXSoftwareRenderer* renderer) {
222	renderer->d.init = DSGXSoftwareRendererInit;
223	renderer->d.reset = DSGXSoftwareRendererReset;
224	renderer->d.deinit = DSGXSoftwareRendererDeinit;
225	renderer->d.invalidateTex = DSGXSoftwareRendererInvalidateTex;
226	renderer->d.setRAM = DSGXSoftwareRendererSetRAM;
227	renderer->d.drawScanline = DSGXSoftwareRendererDrawScanline;
228	renderer->d.getScanline = DSGXSoftwareRendererGetScanline;
229}
230
231static void DSGXSoftwareRendererInit(struct DSGXRenderer* renderer) {
232	struct DSGXSoftwareRenderer* softwareRenderer = (struct DSGXSoftwareRenderer*) renderer;
233	DSGXSoftwarePolygonListInit(&softwareRenderer->activePolys, DS_GX_POLYGON_BUFFER_SIZE / 4);
234	DSGXSoftwareEdgeListInit(&softwareRenderer->activeEdges, DS_GX_POLYGON_BUFFER_SIZE);
235	DSGXSoftwareSpanListInit(&softwareRenderer->activeSpans, DS_GX_POLYGON_BUFFER_SIZE / 2);
236	softwareRenderer->bucket = anonymousMemoryMap(sizeof(*softwareRenderer->bucket) * DS_GX_POLYGON_BUFFER_SIZE);
237	softwareRenderer->scanlineCache = anonymousMemoryMap(sizeof(color_t) * DS_VIDEO_VERTICAL_PIXELS * DS_VIDEO_HORIZONTAL_PIXELS);
238}
239
240static void DSGXSoftwareRendererReset(struct DSGXRenderer* renderer) {
241	struct DSGXSoftwareRenderer* softwareRenderer = (struct DSGXSoftwareRenderer*) renderer;
242	softwareRenderer->flushPending = false;
243}
244
245static void DSGXSoftwareRendererDeinit(struct DSGXRenderer* renderer) {
246	struct DSGXSoftwareRenderer* softwareRenderer = (struct DSGXSoftwareRenderer*) renderer;
247	DSGXSoftwarePolygonListDeinit(&softwareRenderer->activePolys);
248	DSGXSoftwareEdgeListDeinit(&softwareRenderer->activeEdges);	
249	DSGXSoftwareSpanListDeinit(&softwareRenderer->activeSpans);
250	mappedMemoryFree(softwareRenderer->bucket, sizeof(*softwareRenderer->bucket) * DS_GX_POLYGON_BUFFER_SIZE);
251	mappedMemoryFree(softwareRenderer->scanlineCache, sizeof(color_t) * DS_VIDEO_VERTICAL_PIXELS * DS_VIDEO_HORIZONTAL_PIXELS);
252}
253
254static void DSGXSoftwareRendererInvalidateTex(struct DSGXRenderer* renderer, int slot) {
255	struct DSGXSoftwareRenderer* softwareRenderer = (struct DSGXSoftwareRenderer*) renderer;
256	// TODO
257}
258
259static void DSGXSoftwareRendererSetRAM(struct DSGXRenderer* renderer, struct DSGXVertex* verts, struct DSGXPolygon* polys, unsigned polyCount) {
260	struct DSGXSoftwareRenderer* softwareRenderer = (struct DSGXSoftwareRenderer*) renderer;
261
262	softwareRenderer->flushPending = true;
263	softwareRenderer->verts = verts;
264	DSGXSoftwarePolygonListClear(&softwareRenderer->activePolys);
265	DSGXSoftwareEdgeListClear(&softwareRenderer->activeEdges);
266	unsigned i;
267	for (i = 0; i < polyCount; ++i) {
268		struct DSGXSoftwarePolygon* poly = DSGXSoftwarePolygonListAppend(&softwareRenderer->activePolys);
269		struct DSGXSoftwareEdge* edge = DSGXSoftwareEdgeListAppend(&softwareRenderer->activeEdges);
270		poly->poly = &polys[i];
271		poly->texFormat = DSGXTexParamsGetFormat(poly->poly->texParams);
272		poly->texW = 8 << DSGXTexParamsGetSSize(poly->poly->texParams);
273		poly->texH = 8 << DSGXTexParamsGetTSize(poly->poly->texParams);
274		switch (poly->texFormat) {
275		case 0:
276		case 7:
277			poly->texBase = NULL;
278			poly->palBase = NULL;
279			break;
280		case 2:
281			poly->texBase = &renderer->tex[DSGXTexParamsGetVRAMBase(poly->poly->texParams) >> VRAM_BLOCK_OFFSET][(DSGXTexParamsGetVRAMBase(poly->poly->texParams) << 2) & 0xFFFF];
282			poly->palBase = &renderer->texPal[poly->poly->palBase >> 12][(poly->poly->palBase << 2) & 0x1FFF];
283			break;
284		default:
285			poly->texBase = &renderer->tex[DSGXTexParamsGetVRAMBase(poly->poly->texParams) >> VRAM_BLOCK_OFFSET][(DSGXTexParamsGetVRAMBase(poly->poly->texParams) << 2) & 0xFFFF];
286			poly->palBase = &renderer->texPal[poly->poly->palBase >> 11][(poly->poly->palBase << 3) & 0x1FFF];
287			break;
288		}
289		edge->polyId = i;
290
291		struct DSGXVertex* v0 = &verts[poly->poly->vertIds[0]];
292		struct DSGXVertex* v1;
293
294		int v;
295		for (v = 1; v < poly->poly->verts; ++v) {
296			v1 = &verts[poly->poly->vertIds[v]];
297			if (v0->vy >= v1->vy) {
298				edge->y0 = SCREEN_SIZE - v0->vy;
299				edge->x0 = v0->vx;
300				edge->w0 = v0->vw;
301				_expandColor(v0->color, &edge->cr0, &edge->cg0, &edge->cb0);
302				edge->s0 = v0->vs;
303				edge->t0 = v0->vt;
304
305				edge->y1 = SCREEN_SIZE - v1->vy;
306				edge->x1 = v1->vx;
307				edge->w1 = v1->vw;
308				_expandColor(v1->color, &edge->cr1, &edge->cg1, &edge->cb1);
309				edge->s1 = v1->vs;
310				edge->t1 = v1->vt;
311			} else {
312				edge->y0 = SCREEN_SIZE - v1->vy;
313				edge->x0 = v1->vx;
314				edge->w0 = v1->vw;
315				_expandColor(v1->color, &edge->cr0, &edge->cg0, &edge->cb0);
316				edge->s0 = v1->vs;
317				edge->t0 = v1->vt;
318
319				edge->y1 = SCREEN_SIZE - v0->vy;
320				edge->x1 = v0->vx;
321				edge->w1 = v0->vw;
322				_expandColor(v0->color, &edge->cr1, &edge->cg1, &edge->cb1);
323				edge->s1 = v0->vs;
324				edge->t1 = v0->vt;
325			}
326
327			edge = DSGXSoftwareEdgeListAppend(&softwareRenderer->activeEdges);
328			edge->polyId = i;
329			v0 = v1;
330		}
331
332		v1 = &verts[poly->poly->vertIds[0]];
333		if (v0->vy >= v1->vy) {
334			edge->y0 = SCREEN_SIZE - v0->vy;
335			edge->x0 = v0->vx;
336			edge->w0 = v0->vw;
337			_expandColor(v0->color, &edge->cr0, &edge->cg0, &edge->cb0);
338			edge->s0 = v0->vs;
339			edge->t0 = v0->vt;
340
341			edge->y1 = SCREEN_SIZE - v1->vy;
342			edge->x1 = v1->vx;
343			edge->w1 = v1->vw;
344			_expandColor(v1->color, &edge->cr1, &edge->cg1, &edge->cb1);
345			edge->s1 = v1->vs;
346			edge->t1 = v1->vt;
347		} else {
348			edge->y0 = SCREEN_SIZE - v1->vy;
349			edge->x0 = v1->vx;
350			edge->w0 = v1->vw;
351			_expandColor(v1->color, &edge->cr0, &edge->cg0, &edge->cb0);
352			edge->s0 = v1->vs;
353			edge->t0 = v1->vt;
354
355			edge->y1 = SCREEN_SIZE - v0->vy;
356			edge->x1 = v0->vx;
357			edge->w1 = v0->vw;
358			_expandColor(v0->color, &edge->cr1, &edge->cg1, &edge->cb1);
359			edge->s1 = v0->vs;
360			edge->t1 = v0->vt;
361		}
362	}
363	qsort(DSGXSoftwareEdgeListGetPointer(&softwareRenderer->activeEdges, 0), DSGXSoftwareEdgeListSize(&softwareRenderer->activeEdges), sizeof(struct DSGXSoftwareEdge), _edgeSort);
364}
365
366static void DSGXSoftwareRendererDrawScanline(struct DSGXRenderer* renderer, int y) {
367	struct DSGXSoftwareRenderer* softwareRenderer = (struct DSGXSoftwareRenderer*) renderer;
368	if (!softwareRenderer->flushPending) {
369		return;
370	}
371	DSGXSoftwareSpanListClear(&softwareRenderer->activeSpans);
372	memset(softwareRenderer->bucket, 0, sizeof(*softwareRenderer->bucket) * DS_GX_POLYGON_BUFFER_SIZE);
373	int i;
374	for (i = DSGXSoftwareEdgeListSize(&softwareRenderer->activeEdges); i; --i) {
375		size_t idx = i - 1;
376		struct DSGXSoftwareEdge* edge = DSGXSoftwareEdgeListGetPointer(&softwareRenderer->activeEdges, idx);
377		if (edge->y1 >> 12 < y) {
378			DSGXSoftwareEdgeListShift(&softwareRenderer->activeEdges, idx, 1);
379			continue;
380		} else if (edge->y0 >> 12 > y) {
381			continue;
382		}
383
384		unsigned poly = edge->polyId;
385		struct DSGXSoftwareSpan* span = softwareRenderer->bucket[poly];
386		if (span && !span->ep[1].w) {
387			_edgeToSpan(span, edge, 1, y);
388			softwareRenderer->bucket[poly] = NULL;
389		} else if (!span) {
390			span = DSGXSoftwareSpanListAppend(&softwareRenderer->activeSpans);
391			memset(&span->ep[1], 0, sizeof(span->ep[1]));
392			span->poly = DSGXSoftwarePolygonListGetPointer(&softwareRenderer->activePolys, poly);
393			if (!_edgeToSpan(span, edge, 0, y)) {
394				// Horizontal line
395				DSGXSoftwareSpanListShift(&softwareRenderer->activeSpans, DSGXSoftwareSpanListSize(&softwareRenderer->activeSpans) - 1, 1);
396			} else {
397				softwareRenderer->bucket[poly] = span;
398			}
399		}
400	}
401	qsort(DSGXSoftwareSpanListGetPointer(&softwareRenderer->activeSpans, 0), DSGXSoftwareSpanListSize(&softwareRenderer->activeSpans), sizeof(struct DSGXSoftwareSpan), _spanSort);
402
403	color_t* scanline = &softwareRenderer->scanlineCache[DS_VIDEO_HORIZONTAL_PIXELS * y];
404
405	int nextSpanX = DS_VIDEO_HORIZONTAL_PIXELS;
406	if (DSGXSoftwareSpanListSize(&softwareRenderer->activeSpans)) {
407		nextSpanX = DSGXSoftwareSpanListGetPointer(&softwareRenderer->activeSpans, DSGXSoftwareSpanListSize(&softwareRenderer->activeSpans) - 1)->ep[0].x;
408		nextSpanX >>= 12;
409	}
410	for (i = 0; i < DS_VIDEO_HORIZONTAL_PIXELS; ++i) {
411		struct DSGXSoftwareSpan* span = NULL;
412		struct DSGXSoftwareEndpoint ep;
413		int32_t depth = INT32_MIN;
414		scanline[i] = FLAG_UNWRITTEN;
415		if (i >= nextSpanX) {
416			size_t nextSpanId = DSGXSoftwareSpanListSize(&softwareRenderer->activeSpans);
417			span = DSGXSoftwareSpanListGetPointer(&softwareRenderer->activeSpans, nextSpanId - 1);
418			while (i > (span->ep[1].x >> 12) || !span->ep[1].x) {
419				DSGXSoftwareSpanListShift(&softwareRenderer->activeSpans, nextSpanId - 1, 1);
420				--nextSpanId;
421				if (!nextSpanId) {
422					nextSpanX = DS_VIDEO_HORIZONTAL_PIXELS;
423					span = NULL;
424					break;
425				}
426				span = DSGXSoftwareSpanListGetPointer(&softwareRenderer->activeSpans, nextSpanId - 1);
427				nextSpanX = span->ep[0].x >> 12;
428			}
429			if (i < nextSpanX) {
430				span = NULL;
431			} else {
432				struct DSGXSoftwareSpan* testSpan = DSGXSoftwareSpanListGetPointer(&softwareRenderer->activeSpans, nextSpanId - 1);
433				while (i > (testSpan->ep[0].x >> 12)) {
434					if (i <= (testSpan->ep[1].x >> 12)) {
435						_lerpEndpoint(testSpan, &ep, i);
436						color_t color = _lookupColor(&ep, testSpan->poly);
437						if (scanline[i] == FLAG_UNWRITTEN) {
438							scanline[i] = color;
439						}
440						if (ep.w >= depth) {
441							depth = ep.w;
442							span = testSpan;
443							if (color != FLAG_UNWRITTEN) {
444								scanline[i] = color;
445							}
446						}
447					}
448					--nextSpanId;
449					if (!nextSpanId) {
450						break;
451					}
452					testSpan = DSGXSoftwareSpanListGetPointer(&softwareRenderer->activeSpans, nextSpanId - 1);
453				}
454			}
455		}
456	}
457	if (y == DS_VIDEO_VERTICAL_PIXELS - 1) {
458		softwareRenderer->flushPending = false;
459	}
460}
461
462static void DSGXSoftwareRendererGetScanline(struct DSGXRenderer* renderer, int y, color_t** output) {
463	struct DSGXSoftwareRenderer* softwareRenderer = (struct DSGXSoftwareRenderer*) renderer;
464	*output = &softwareRenderer->scanlineCache[DS_VIDEO_HORIZONTAL_PIXELS * y];
465}