[common] rects: refactor rect buffer copy code to common module

This also fixes a bug of accidentally multiplying the stride by 4 when
the stride is already in bytes and not pixels.

common/include/common/rects.h

@@ -0,0 +1,45 @@
+/**
+ * Looking Glass
+ * Copyright © 2017-2021 The Looking Glass Authors
+ * https://looking-glass.io
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc., 59
+ * Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#ifndef _LG_COMMON_RECTS_H_
+#define _LG_COMMON_RECTS_H_
+
+#include <stdint.h>
+#include <string.h>
+
+#include "common/framebuffer.h"
+#include "common/types.h"
+
+inline static void rectCopyUnaligned(uint8_t * dest, const uint8_t * src,
+    int ystart, int yend, int dx, int dstStride, int srcStride, int width)
+{
+  for (int i = ystart; i < yend; ++i)
+  {
+    unsigned int srcOffset = i * srcStride + dx;
+    unsigned int dstOffset = i * dstStride + dx;
+    memcpy(dest + dstOffset, src + srcOffset, width);
+  }
+}
+
+void rectsBufferToFramebuffer(FrameDamageRect * rects, int count,
+  FrameBuffer * frame, int dstStride, int height,
+  const uint8_t * src, int srcStride);
+
+#endif