M include/mgba/internal/gba/renderers/video-software.h → include/mgba/internal/gba/renderers/video-software.h

@@ -15,6 +15,9 @@ #include <mgba/gba/interface.h>
 #include <mgba/internal/gba/io.h>
 #include <mgba/internal/gba/renderers/common.h>
 #include <mgba/internal/gba/video.h>
+#ifdef M_CORE_DS
+#include <mgba/internal/ds/video.h>
+#endif
 
 struct GBAVideoSoftwareBackground {
 	unsigned index;
@@ -158,7 +161,11 @@ uint16_t nextIo[REG_SOUND1CNT_LO >> 1];
 	struct ScanlineCache {
 		uint16_t io[REG_SOUND1CNT_LO >> 1];
 		int32_t scale[2][2];
+#ifdef M_CORE_DS
+	} cache[DS_VIDEO_VERTICAL_PIXELS];
+#else
 	} cache[GBA_VIDEO_VERTICAL_PIXELS];
+#endif
 	int nextY;
 
 	int start;

M src/ds/renderers/software.c → src/ds/renderers/software.c

@@ -378,6 +378,18 @@
 static void DSVideoSoftwareRendererDrawGBAScanline(struct GBAVideoRenderer* renderer, struct DSGX* gx, int y) {
 	struct GBAVideoSoftwareRenderer* softwareRenderer = (struct GBAVideoSoftwareRenderer*) renderer;
 
+	if (y == DS_VIDEO_VERTICAL_PIXELS - 1) {
+		softwareRenderer->nextY = 0;
+	} else {
+		softwareRenderer->nextY = y + 1;
+	}
+
+	bool dirty = softwareRenderer->scanlineDirty[y >> 5] & (1 << (y & 0x1F));
+	if (memcmp(softwareRenderer->nextIo, softwareRenderer->cache[y].io, sizeof(softwareRenderer->nextIo))) {
+		memcpy(softwareRenderer->cache[y].io, softwareRenderer->nextIo, sizeof(softwareRenderer->nextIo));
+		dirty = true;
+	}
+
 	int x;
 	color_t* row = &softwareRenderer->outputBuffer[softwareRenderer->outputBufferStride * y];
 	if (GBARegisterDISPCNTIsForcedBlank(softwareRenderer->dispcnt)) {