1 files changed, 76 insertions, 0 deletions
diff --git a/backends/PalmOS/Src/arm/renderparallax.cpp b/backends/PalmOS/Src/arm/renderparallax.cpp
new file mode 100755
index 0000000000..8c710d7c2e
--- /dev/null
+++ b/backends/PalmOS/Src/arm/renderparallax.cpp
@@ -0,0 +1,76 @@
+#include "native.h"
+#include "endianutils.h"
+
+#define MAIN_TYPE	ParallaxType
+#include "macros.h"
+
+#define READ_LE_UINT32(ptr)	*(const uint32 *)(ptr)
+
+UInt32 Screen_renderParallax(void *userData68KP) {
+// import variables
+	SETPTR	(UInt8 *	,data		);
+	SETPTR	(UInt32 *	,lineIndexes);
+	SETPTR	(UInt8 *	,_screenBuf	);
+	SET16	(UInt16,	_scrnSizeX	);
+	SET16	(UInt16,	scrnScrlX	);
+	SET16	(UInt16,	scrnScrlY	);
+	SET16	(UInt16,	paraScrlX	);
+	SET16	(UInt16,	paraScrlY	);
+	SET16	(UInt16,	scrnWidth	);
+	SET16	(UInt16,	scrnHeight	);
+// end of import
+
+	for (uint16 cnty = 0; cnty < scrnHeight; cnty++) {
+		uint8 *src = data + READ_LE_UINT32(lineIndexes + cnty + paraScrlY);
+		uint8 *dest = _screenBuf + scrnScrlX + (cnty + scrnScrlY) * _scrnSizeX;
+		uint16 remain = paraScrlX;
+		uint16 xPos = 0;
+		bool copyFirst = false;
+		while (remain) { // skip past the first part of the parallax to get to the right scrolling position
+			uint8 doSkip = *src++;
+			if (doSkip <= remain)
+				remain -= doSkip;
+			else {
+				xPos = doSkip - remain;
+				dest += xPos;
+				remain = 0;
+			}
+			if (remain) {
+				uint8 doCopy = *src++;
+				if (doCopy <= remain) {
+					remain -= doCopy;
+					src += doCopy;
+				} else {
+					uint16 remCopy = doCopy - remain;
+					MemMove(dest, src + remain, remCopy);
+					dest += remCopy;
+					src += doCopy;
+					xPos = remCopy;
+					remain = 0;
+				}
+			} else
+				copyFirst = true;
+		}
+		while (xPos < scrnWidth) {
+			if (!copyFirst) {
+				if (uint8 skip = *src++) {
+					dest += skip;
+					xPos += skip;
+				}
+			} else
+				copyFirst = false;
+			if (xPos < scrnWidth) {
+				if (uint8 doCopy = *src++) {
+					if (xPos + doCopy > scrnWidth)
+						doCopy = scrnWidth - xPos;
+					MemMove(dest, src, doCopy);
+					dest += doCopy;
+					xPos += doCopy;
+					src += doCopy;
+				}
+			}
+		}
+	}
+	
+	return 0;
+}