func drawPiece(s *sdl.Surface, col, row int, p c4.Piece) {
	// Load images
	if redImage == nil {
		redImage = sdl.Load("red.png")
	}
	if blackImage == nil {
		blackImage = sdl.Load("black.png")
	}
	if noneImage == nil {
		noneImage = sdl.Load("empty.png")
	}

	// Select image
	var image *sdl.Surface
	if p == c4.Red {
		image = redImage
	} else if p == c4.Black {
		image = blackImage
	} else {
		image = noneImage
	}

	// Draw image
	s.Blit(
		&sdl.Rect{
			int16(SCREEN_WIDTH * col / c4.MaxColumns),
			int16(SCREEN_HEIGHT * (c4.MaxRows - row - 1) / c4.MaxRows),
			0,
			0},
		image,
		nil)
}

func apply_surface(x, y int16, src, dest *sdl.Surface) {
	var offset sdl.Rect

	offset.X = x
	offset.Y = y

	dest.Blit(&offset, src, nil)
}

func undrawColor(ss *sdl.Surface, w, h int32, col uint32) {

	var x, y int32
	for y = 0; y < h; y++ {
		for x = 0; x < w; x++ {
			col := sdlGet(x, y, ss) & (^col)
			sdlSet2(x, y, col, ss)
		}
	}
	ss.Flip()
}

func wrap(cSurface *C.SDL_Surface) *sdl.Surface {
	var s *sdl.Surface

	if cSurface != nil {
		var surface sdl.Surface
		surface.SetCSurface(unsafe.Pointer(cSurface))
		s = &surface
	} else {
		s = nil
	}

	return s
}

func (p *Piece) render(screen *sdl.Surface) {
	if p == nil {
		return
	}
	for i := 0; i < 4; i++ {
		x := p.pos.x + p.tet.position[p.rot][i].x
		y := p.pos.y + p.tet.position[p.rot][i].y
		rect := sdl.Rect{
			int16(x * PixPerBrick),
			int16(y * PixPerBrick),
			uint16(PixPerBrick),
			uint16(PixPerBrick)}
		screen.FillRect(&rect, colorToUint32(colorTable[p.tet.color]))
	}
}

func draw_sdl(o *Object, s *sdl.Surface) {
	var ss *sdl.Surface
	if o.Collides {
		ss = surfaceb
	} else {
		ss = surface
	}

	s.Blit(
		&sdl.Rect{int16(float64(o.Pos.X) * ssw),
			int16(float64(o.Pos.Y) * ssh),
			uint16(float64((o.Pos.X + o.Size.X)) * ssw),
			uint16(float64((o.Pos.Y + o.Size.Y)) * ssh)},
		ss,
		&sdl.Rect{0, 0, uint16(o.Size.X), uint16(o.Size.Y)})
}

// Set distance of nearby points (from point ax,ay -> bx,by) in given dir (0=N,
// 1=S, 2=E, 3=W)
func setDist(ss *sdl.Surface, rmc [][]int32, dist [][][]int32, aX, aY, bX, bY, dir, w, h, r, currBestDist, lastSetX, lastSetY int32, done, found bool, round int) (newDone, newFound bool, newBest int32, setX, setY int32) {

	newDone, newFound, newBest, setX, setY = done, found, currBestDist, lastSetX, lastSetY

	if !inRect(bX, bY, w, h) {
		return
	}

	dA := dist[aX][aY]
	_, best := bestDist(dA)
	best += 4 * (r + 1) * (r + 1)

	if best >= currBestDist { // we alredy have better distance (smaller is better)
		return
	}

	dB := dist[bX][bY]
	rmCount := removeCount(ss, rmc, w, h, bX, bY, r)

	if currBestDist == DistMax && rmCount > 0 && best < DistMax {
		//fmt.Printf("==== found rmCount=%d best=%d bX=%d bY=%d\n", rmCount, best, bX, bY)
		newBest = best
		newFound = true
	}

	//fmt.Printf("setDist aX=%d aY=%d bX=%d bY=%d rmCount=%d\n", aX, aY, bX, bY, rmCount)

	if best < dB[dir] && rmCount != -1 { // part of model would be removed
		if aX&7 == 0 && aY&7 == 0 {
			if round > 20 {
				fmt.Printf("setDist x=%d y=%d value=%d dB[dir]=%d\n", aX, aY, best, dB[dir])
			}
			sdlSet(aX, aY, ColDebug, ss)
			if aX&63 == 0 && aY&63 == 0 {
				ss.Flip()
			}
		}
		dB[dir] = best - rmCount // favourize paths that remove more material
		newDone = false
		setX, setY = bX, bY
	}
	return
}

func (renderer *SDLRenderer) renderLine(pos int, line string) {
	x := renderer.commandLineRect.X
	y := int16(renderer.commandLineRect.Y) - int16(renderer.fontHeight*uint(pos))
	w := renderer.commandLineRect.W
	h := renderer.commandLineRect.H

	renderer.internalSurface.FillRect(&sdl.Rect{x, y, w, h}, 0)

	if len(line) == 0 {
		return
	}

	var textSurface *sdl.Surface
	if renderer.Blended {
		textSurface = ttf.RenderUTF8_Blended(renderer.Font, line, renderer.Color)
	} else {
		textSurface = ttf.RenderUTF8_Solid(renderer.Font, line, renderer.Color)
	}

	if textSurface != nil {
		renderer.internalSurface.Blit(&sdl.Rect{x, y, w, h}, textSurface, nil)
		textSurface.Free()
	}
}

// Find path from cX,cY to tX,tY so that no part of model is removed
func findAndRemove(ss *sdl.Surface, tc *Tco, rmc [][]int32, cX, cY, w, h, r int32) (bool, bool, int32, int32) {

	//fmt.Printf("findPath cX=%d cY=%d tX=%d tY=%d\n", cX, cY, tX, tY)

	// The algorithm is flood-fill like:
	// For earch pixel we remember shortest distance to target point in 4
	// directions (N,S,E,W). Starting at point (tX,tY) all the distances are 0,
	// e.g. for (tX+1,cY) the distnace in W is 1, others are 3 etc..
	//
	//
	//            S=1
	//             T  W=1 W=2
	//            N=1     N=3
	//
	// It works like that: N=3 means if you go N the shortest path to T is 3
	// (after going twice west). From the same point it also implies that W=3
	// (after going WN), S=5 (e.g. after going NNWW), E=5 (after WNWW).
	dist := make([][][]int32, w)
	for x := range dist {
		dist[x] = make([][]int32, h)
		for y := range dist[x] {
			if int32(x) == cX && int32(y) == cY {
				dist[x][y] = []int32{0, 0, 0, 0, 0, 0, 0, 0} // value for each dir + removeCount for given point
			} else {
				dist[x][y] = []int32{DistMax, DistMax, DistMax, DistMax, DistMax, DistMax, DistMax, DistMax}
			}
		}
	}

	undrawDebug(ss, w, h)
	currBestDist := DistMax
	found := false
	lastSetX, lastSetY := cX, cY
	for round := 0; ; round++ {

		done := true
		var centerX, centerY int32

		undrawBlue(ss, w, h)
		//drawLine(ss, rmc, cX, cY, tX, tY)

		if round%8 == 0 {
			centerX, centerY = cX, cY
		} else if round%8 == 0 {
			centerX, centerY = 0, 0
		} else if round%8 == 1 {
			centerX, centerY = 0, w-1
		} else if round%8 == 2 {
			centerX, centerY = 0, h-1
		} else if round%8 == 3 {
			centerX, centerY = w-1, h-1
		} else {
			centerX, centerY = lastSetX, lastSetY
		}

		for x, y, a, ok := nearRectBegin(centerX, centerY, w, h, 0); ok; x, y, a, ok = nearRectNext(centerX, centerY, x, y, a, w, h) {

			/*fmt.Printf(" N  S  E  W  NW NE SE SW|  N  S  E  W  NW NE SE SW|  N  S  E  W  NW NE SE SW|  N  S  E  W  NW NE SE SW|  N  S  E  W  NW NE SE SW\n")
			for i := cY - 3; i <= cY+3; i++ {
				for j := cX - 3; j <= cX+3; j++ {
					if !inRect(i, j, w, h) {
						continue
					}
					dumpDists(dist[j][i])
					fmt.Printf("| ")
				}
				fmt.Println()
			}
			fmt.Printf("x=%d y=%d a=%d done=%t currBestDist=%d\n", x, y, a, done, currBestDist)
			fmt.Scanln()*/

			done, found, currBestDist, lastSetX, lastSetY = setDist(ss, rmc, dist, x, y, x, y+1, dirN, w, h, r, currBestDist, lastSetX, lastSetY, done, found, round)
			done, found, currBestDist, lastSetX, lastSetY = setDist(ss, rmc, dist, x, y, x, y-1, dirS, w, h, r, currBestDist, lastSetX, lastSetY, done, found, round)
			done, found, currBestDist, lastSetX, lastSetY = setDist(ss, rmc, dist, x, y, x-1, y, dirE, w, h, r, currBestDist, lastSetX, lastSetY, done, found, round)
			done, found, currBestDist, lastSetX, lastSetY = setDist(ss, rmc, dist, x, y, x+1, y, dirW, w, h, r, currBestDist, lastSetX, lastSetY, done, found, round)
			done, found, currBestDist, lastSetX, lastSetY = setDist(ss, rmc, dist, x, y, x+1, y+1, dirNW, w, h, r, currBestDist, lastSetX, lastSetY, done, found, round)
			done, found, currBestDist, lastSetX, lastSetY = setDist(ss, rmc, dist, x, y, x-1, y-1, dirSE, w, h, r, currBestDist, lastSetX, lastSetY, done, found, round)
			done, found, currBestDist, lastSetX, lastSetY = setDist(ss, rmc, dist, x, y, x-1, y+1, dirNE, w, h, r, currBestDist, lastSetX, lastSetY, done, found, round)
			done, found, currBestDist, lastSetX, lastSetY = setDist(ss, rmc, dist, x, y, x+1, y-1, dirSW, w, h, r, currBestDist, lastSetX, lastSetY, done, found, round)
		}

		fmt.Printf("round=%d done=%t found=%t currBestDist=%d, lastSetX=%d lastSetY=%d\n", round, done, found, currBestDist, lastSetX, lastSetY)

		if done {
			break
		}
	}

	dstMin := DistMax
	tX, tY := int32(-1), int32(-1)
	removed := false
	for x, y, a, ok := nearRectBegin(cX, cY, w, h, 1); ok; x, y, a, ok = nearRectNext(cX, cY, x, y, a, w, h) {

		if removeCount(ss, rmc, w, h, x, y, r) <= 0 {
			continue
		}
		removed = true
		dst := DistMax
		if found {
//.........这里部分代码省略.........