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)}
}

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 (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 (c *Canvas) fontHeight(font *Font) (height int, err error) {
	err = c.withFontAndTextColor(font, 0, func() error {
		var size win.SIZE
		if !win.GetTextExtentPoint32(c.hdc, gM, 2, &size) {
			return newError("GetTextExtentPoint32 failed")
		}

		height = int(size.CY)
		if height == 0 {
			return newError("invalid font height")
		}

		return nil
	})

	return
}