func (wb *WindowBase) calculateTextSizeImpl(text string) Size {
	hdc := win.GetDC(wb.hWnd)
	if hdc == 0 {
		newError("GetDC failed")
		return Size{}
	}
	defer win.ReleaseDC(wb.hWnd, hdc)

	hFontOld := win.SelectObject(hdc, win.HGDIOBJ(wb.window.Font().handleForDPI(0)))
	defer win.SelectObject(hdc, hFontOld)

	var size Size
	lines := strings.Split(text, "\n")

	for _, line := range lines {
		var s win.SIZE
		str := syscall.StringToUTF16(strings.TrimRight(line, "\r "))

		if !win.GetTextExtentPoint32(hdc, &str[0], int32(len(str)-1), &s) {
			newError("GetTextExtentPoint32 failed")
			return Size{}
		}

		size.Width = maxi(size.Width, int(s.CX))
		size.Height += int(s.CY)
	}

	return size
}

func (cb *ComboBox) calculateMaxItemTextWidth() int {
	hdc := win.GetDC(cb.hWnd)
	if hdc == 0 {
		newError("GetDC failed")
		return -1
	}
	defer win.ReleaseDC(cb.hWnd, hdc)

	hFontOld := win.SelectObject(hdc, win.HGDIOBJ(cb.Font().handleForDPI(0)))
	defer win.SelectObject(hdc, hFontOld)

	var maxWidth int

	count := cb.model.ItemCount()
	for i := 0; i < count; i++ {
		var s win.SIZE
		str := syscall.StringToUTF16(cb.itemString(i))

		if !win.GetTextExtentPoint32(hdc, &str[0], int32(len(str)-1), &s) {
			newError("GetTextExtentPoint32 failed")
			return -1
		}

		maxWidth = maxi(maxWidth, int(s.CX))
	}

	return maxWidth
}

func (wb *WindowBase) dialogBaseUnits() Size {
	// The window may use a font different from that in WindowBase,
	// like e.g. NumberEdit does, so we try to use the right one.
	window := windowFromHandle(wb.hWnd)

	hdc := win.GetDC(wb.hWnd)
	defer win.ReleaseDC(wb.hWnd, hdc)

	hFont := window.Font().handleForDPI(0)
	hFontOld := win.SelectObject(hdc, win.HGDIOBJ(hFont))
	defer win.SelectObject(hdc, win.HGDIOBJ(hFontOld))

	var tm win.TEXTMETRIC
	if !win.GetTextMetrics(hdc, &tm) {
		newError("GetTextMetrics failed")
	}

	var size win.SIZE
	if !win.GetTextExtentPoint32(
		hdc,
		dialogBaseUnitsUTF16StringPtr,
		52,
		&size) {
		newError("GetTextExtentPoint32 failed")
	}

	return Size{int((size.CX/26 + 1) / 2), int(tm.TmHeight)}
}

// Screenshot returns an image of the window.
func (wb *WindowBase) Screenshot() (*image.RGBA, error) {
	if hBmp, err := hBitmapFromWindow(wb); err != nil {
		return nil, err
	} else {

		var bi win.BITMAPINFO
		bi.BmiHeader.BiSize = uint32(unsafe.Sizeof(bi.BmiHeader))
		hdc := win.GetDC(0)
		if ret := win.GetDIBits(hdc, hBmp, 0, 0, nil, &bi, win.DIB_RGB_COLORS); ret == 0 {
			return nil, newError("GetDIBits get bitmapinfo failed")
		}

		buf := make([]byte, bi.BmiHeader.BiSizeImage)
		bi.BmiHeader.BiCompression = win.BI_RGB
		if ret := win.GetDIBits(hdc, hBmp, 0, uint32(bi.BmiHeader.BiHeight), &buf[0], &bi, win.DIB_RGB_COLORS); ret == 0 {
			return nil, newError("GetDIBits failed")
		}

		width := int(bi.BmiHeader.BiWidth)
		height := int(bi.BmiHeader.BiHeight)
		im := image.NewRGBA(image.Rect(0, 0, width, height))
		n := 0
		for y := 0; y < height; y++ {
			for x := 0; x < width; x++ {
				r := buf[n+2]
				g := buf[n+1]
				b := buf[n+0]
				n += 4
				im.Set(x, height-y, color.RGBA{r, g, b, 255})
			}
		}
		return im, nil
	}
}

func (le *LineEdit) initCharWidth() {

	font := le.Font()
	if font == le.charWidthFont {
		return
	}
	le.charWidthFont = font
	le.charWidth = 8

	hdc := win.GetDC(le.hWnd)
	if hdc == 0 {
		newError("GetDC failed")
		return
	}
	defer win.ReleaseDC(le.hWnd, hdc)

	defer win.SelectObject(hdc, win.SelectObject(hdc, win.HGDIOBJ(font.handleForDPI(0))))

	buf := []uint16{'M'}

	var s win.SIZE
	if !win.GetTextExtentPoint32(hdc, &buf[0], int32(len(buf)), &s) {
		newError("GetTextExtentPoint32 failed")
		return
	}
	le.charWidth = int(s.CX)
}

func newCanvasFromHWND(hwnd win.HWND) (*Canvas, error) {
	hdc := win.GetDC(hwnd)
	if hdc == 0 {
		return nil, newError("GetDC failed")
	}

	return (&Canvas{hdc: hdc, hwnd: hwnd}).init()
}

func init() {
	// Retrieve screen DPI
	hDC := win.GetDC(0)
	defer win.ReleaseDC(0, hDC)
	screenDPIX = int(win.GetDeviceCaps(hDC, win.LOGPIXELSX))
	screenDPIY = int(win.GetDeviceCaps(hDC, win.LOGPIXELSY))

	// Initialize default font
	var err error
	if defaultFont, err = NewFont("MS Shell Dlg 2", 8, 0); err != nil {
		panic("failed to create default font")
	}
}

func hBitmapFromImage(im image.Image) (win.HBITMAP, error) {
	var bi win.BITMAPV5HEADER
	bi.BiSize = uint32(unsafe.Sizeof(bi))
	bi.BiWidth = int32(im.Bounds().Dx())
	bi.BiHeight = -int32(im.Bounds().Dy())
	bi.BiPlanes = 1
	bi.BiBitCount = 32
	bi.BiCompression = win.BI_BITFIELDS
	// The following mask specification specifies a supported 32 BPP
	// alpha format for Windows XP.
	bi.BV4RedMask = 0x00FF0000
	bi.BV4GreenMask = 0x0000FF00
	bi.BV4BlueMask = 0x000000FF
	bi.BV4AlphaMask = 0xFF000000

	hdc := win.GetDC(0)
	defer win.ReleaseDC(0, hdc)

	var lpBits unsafe.Pointer

	// Create the DIB section with an alpha channel.
	hBitmap := win.CreateDIBSection(hdc, &bi.BITMAPINFOHEADER, win.DIB_RGB_COLORS, &lpBits, 0, 0)
	switch hBitmap {
	case 0, win.ERROR_INVALID_PARAMETER:
		return 0, newError("CreateDIBSection failed")
	}

	// Fill the image
	bitmap_array := (*[1 << 30]byte)(unsafe.Pointer(lpBits))
	i := 0
	for y := im.Bounds().Min.Y; y != im.Bounds().Max.Y; y++ {
		for x := im.Bounds().Min.X; x != im.Bounds().Max.X; x++ {
			r, g, b, a := im.At(x, y).RGBA()
			bitmap_array[i+3] = byte(a >> 8)
			bitmap_array[i+2] = byte(r >> 8)
			bitmap_array[i+1] = byte(g >> 8)
			bitmap_array[i+0] = byte(b >> 8)
			i += 4
		}
	}

	return hBitmap, nil
}

func hBitmapFromWindow(window Window) (win.HBITMAP, error) {
	hdcMem := win.CreateCompatibleDC(0)
	if hdcMem == 0 {
		return 0, newError("CreateCompatibleDC failed")
	}
	defer win.DeleteDC(hdcMem)

	var r win.RECT
	if !win.GetWindowRect(window.Handle(), &r) {
		return 0, newError("GetWindowRect failed")
	}

	hdc := win.GetDC(window.Handle())
	width, height := r.Right-r.Left, r.Bottom-r.Top
	hBmp := win.CreateCompatibleBitmap(hdc, width, height)
	win.ReleaseDC(window.Handle(), hdc)

	hOld := win.SelectObject(hdcMem, win.HGDIOBJ(hBmp))
	flags := win.PRF_CHILDREN | win.PRF_CLIENT | win.PRF_ERASEBKGND | win.PRF_NONCLIENT | win.PRF_OWNED
	window.SendMessage(win.WM_PRINT, uintptr(hdcMem), uintptr(flags))

	win.SelectObject(hdcMem, hOld)
	return hBmp, nil
}