KXL_ClearFrameRect -- Rectangles with an arbitrary frame are cleared.
It clears by the color set up by KXL_SetDrawColor.
For the compatibility of 1.1.4 or earlier.

void KXL_ClearFrame(KXL_Rect rect);

#include <KXL.h>

int main(void)
{
  KXL_Rect rect = {0, 0, 100, 100};

  KXL_CreateWindow(rect.Width, rect.Height, "sample", 0);
  KXL_SetDrawColor(0xff, 0x00, 0x00);
  KXL_DrawRectangle(30, 30, 30, 30, True);
  KXL_UpDateRect(rect);
  getchar();
  KXL_ClearFrame(rect);
  KXL_UpDateRect(rect);
  getchar();
  KXL_DeleteWindow();
  return 0;
}