term_windows.go

term_windows.go

//go:build windows
// +build windows

package term

import (
	"fmt"
	"unsafe"

	"golang.org/x/sys/windows"
)

const (
	foregroundBlue      = uint16(0x0001)
	foregroundGreen     = uint16(0x0002)
	foregroundRed       = uint16(0x0004)
	foregroundIntensity = uint16(0x0008)
	backgroundBlue      = uint16(0x0010)
	backgroundGreen     = uint16(0x0020)
	backgroundRed       = uint16(0x0040)
	backgroundIntensity = uint16(0x0080)
	underscore          = uint16(0x8000)

	foregroundMask = foregroundBlue | foregroundGreen | foregroundRed | foregroundIntensity
	backgroundMask = backgroundBlue | backgroundGreen | backgroundRed | backgroundIntensity
)

// textAttributes defines attributes of the characters written to a screen buffer.
// https://docs.microsoft.com/en-us/windows/console/console-screen-buffer-info-str
type textAttributes struct {
	foregroundColor     uint16
	backgroundColor     uint16
	foregroundIntensity uint16
	backgroundIntensity uint16
	underscore          uint16
	otherAttributes     uint16
}

// coord defines the coordinates of a character cell in a console screen buffer.
// https://docs.microsoft.com/en-us/windows/console/coord-str
type coord struct {
	X, Y int16
}

// smallRect defines the coordinates of the upper left and lower right corners of a rectangle.
// https://docs.microsoft.com/en-us/windows/console/small-rect-str
type smallRect struct {
	Left, Top, Right, Bottom int16
}

// consoleScreenBufferInfo contains information about a console screen buffer.
// https://docs.microsoft.com/en-us/windows/console/console-screen-buffer-info-str
type consoleScreenBufferInfo struct {
	DwSize              coord
	DwCursorPosition    coord
	WAttributes         uint16
	SrWindow            smallRect
	DwMaximumWindowSize coord
}

var (
	kernel32    = windows.NewLazyDLL("kernel32.dll")
	defaultAttr *textAttributes
)

func init() {
	screenInfo := getConsoleScreenBufferInfo(uintptr(windows.Stdout))
	if screenInfo != nil {
		defaultAttr = &textAttributes{
			foregroundColor:     screenInfo.WAttributes & (foregroundRed | foregroundGreen | foregroundBlue),
			backgroundColor:     screenInfo.WAttributes & (backgroundRed | backgroundGreen | backgroundBlue),
			foregroundIntensity: screenInfo.WAttributes & foregroundIntensity,
			backgroundIntensity: screenInfo.WAttributes & backgroundIntensity,
			underscore:          screenInfo.WAttributes & underscore,
			otherAttributes:     screenInfo.WAttributes &^ (foregroundMask | backgroundMask | underscore),
		}
	}
}

// getConsoleScreenBufferInfo retrieves information about the specified console screen buffer.
// https://docs.microsoft.com/en-us/windows/console/getconsolescreenbufferinfo
func getConsoleScreenBufferInfo(hConsoleOutput uintptr) *consoleScreenBufferInfo {
	var csbi consoleScreenBufferInfo
	ret, _, _ := kernel32.NewProc("GetConsoleScreenBufferInfo").Call(
		hConsoleOutput,
		uintptr(unsafe.Pointer(&csbi)))
	if ret == 0 {
		return nil
	}
	return &csbi
}