Merge 5330efee94e37e98c0e363b724d5fc1168bc6660 into 2b8f0c7960e9553acea6d579a740713066da5e13

block.go

@@ -27,6 +27,8 @@ type Block struct {
 	Title      string
 	TitleStyle Style
 
+	ANSIString string
+
 	sync.Mutex
 }
 
@@ -103,3 +105,8 @@ func (self *Block) SetRect(x1, y1, x2, y2 int) {
 func (self *Block) GetRect() image.Rectangle {
 	return self.Rectangle
 }
+
+// GetANSIString implements the Drawable interface.
+func (self *Block) GetANSIString() string {
+	return self.ANSIString
+}

render.go

@@ -5,6 +5,7 @@
 package termui
 
 import (
+	"fmt"
 	"image"
 	"sync"
 
@@ -16,10 +17,44 @@ type Drawable interface {
 	SetRect(int, int, int, int)
 	Draw(*Buffer)
 	sync.Locker
+	GetANSIString() string
 }
 
 func Render(items ...Drawable) {
+	// draw background, etc for items with ANSI escape strings
 	for _, item := range items {
+		if len(item.GetANSIString()) > 0 {
+			continue
+		}
+		buf := NewBuffer(item.GetRect())
+		item.Lock()
+		item.Draw(buf)
+		item.Unlock()
+		for point, cell := range buf.CellMap {
+			if point.In(buf.Rectangle) {
+				tb.SetCell(
+					point.X, point.Y,
+					cell.Rune,
+					tb.Attribute(cell.Style.Fg+1)|tb.Attribute(cell.Style.Modifier), tb.Attribute(cell.Style.Bg+1),
+				)
+			}
+		}
+	}
+	tb.Flush()
+
+	// draw images, etc over the already filled cells with ANSI escape strings (sixel, ...)
+	for _, item := range items {
+		if ansiString := item.GetANSIString(); len(ansiString) > 0 {
+			fmt.Printf("%s", ansiString)
+			continue
+		}
+	}
+
+	// draw items without ANSI strings last in case the ANSI escape strings ended messed up
+	for _, item := range items {
+		if len(item.GetANSIString()) == 0 {
+			continue
+		}
 		buf := NewBuffer(item.GetRect())
 		item.Lock()
 		item.Draw(buf)

widgets/exp/HACKING.md

@@ -0,0 +1,19 @@
+possible enhancements:
+
+kitty https://sw.kovidgoyal.net/kitty/graphics-protocol.html
+
+Terminology (from Enlightenment) https://www.enlightenment.org/docs/apps/terminology.md#tycat https://github.com/billiob/terminology
+
+urxvt pixbuf / ...
+
+Tektronix 4014
+
+ReGis
+
+reimplement 23imgdisplay:
+
+check for X11 and not Alacritty (https://github.com/jwilm/alacritty/issues/1021)
+
+---
+
+if i remember correctly xterm has a size limit for sixel images - pixel width???

widgets/exp/aaa_init.go

@@ -0,0 +1,36 @@
+// <Copyright> 2018,2019 Simon Robin Lehn. All rights reserved.
+// Use of this source code is governed by a MIT license that can
+// be found in the LICENSE file.
+
+package exp
+
+import (
+	. "github.com/gizak/termui/v3"
+	"github.com/gizak/termui/v3/widgets"
+)
+
+// the file name should appear at the top when alphabetically sorted (start with "aaa")
+// because the init() functions are executed in alphabetic file order
+func init() {
+	scanTerminal()
+	var drawFallback func(*widgets.Image, *Buffer) (error)
+	if drbl, ok := widgets.GetDrawers()["block"]; ok {
+		drawFallback = drbl.Draw
+	}
+	widgets.RegisterDrawer(
+		"block",
+		widgets.Drawer{
+			Remote:         true,
+			IsEscapeString: false,
+			Available:      func() bool {return true},
+			Draw:           func(img *widgets.Image, buf *Buffer) (err error) {
+				// possible reattachments of the terminal multiplexer?
+				if isMuxed {
+					scanTerminal()
+				}
+
+				return drawFallback(img, buf)
+			},
+		},
+	)
+}

widgets/exp/drawer_iterm2.go

@@ -0,0 +1,60 @@
+// <Copyright> 2019 Simon Robin Lehn. All rights reserved.
+// Use of this source code is governed by a MIT license that can
+// be found in the LICENSE file.
+
+package exp
+
+import (
+	"fmt"
+	"bytes"
+	"encoding/base64"
+	"errors"
+	"image/png"
+
+	. "github.com/gizak/termui/v3"
+	"github.com/gizak/termui/v3/widgets"
+)
+
+
+func init() {
+	widgets.RegisterDrawer(
+		"iterm2",
+		widgets.Drawer{
+			Remote:         true,
+			IsEscapeString: true,
+			Available:      func() bool {return isIterm2 || isMacTerm},
+			Draw:           drawITerm2,
+		},
+	)
+}
+
+func drawITerm2(wdgt *widgets.Image, buf *Buffer) (err error) {
+	wdgt.Block.Draw(buf)
+
+	img, changed, err := resizeImage(wdgt, buf)
+	if !changed || err != nil {
+		return err
+	}
+
+	imageDimensions := wdgt.GetVisibleArea()
+
+	// https://www.iterm2.com/documentation-images.html
+	if isIterm2 || isMacTerm {
+		buf := new(bytes.Buffer)
+		if err = png.Encode(buf, img); err != nil {
+			goto skipIterm2
+		}
+		imgBase64 := base64.StdEncoding.EncodeToString(buf.Bytes())
+		nameBase64 := base64.StdEncoding.EncodeToString([]byte(wdgt.Block.Title))
+		// 0 for stretching - 1 for no stretching
+		noStretch := 0
+		iterm2String := wrap(fmt.Sprintf("\033]1337;File=name=%s;inline=1;height=%d;width=%d;preserveAspectRatio=%d:%s\a", nameBase64, imageDimensions.Max.Y, nameBase64, imageDimensions.Max.X, noStretch, imgBase64))
+		// for width, height:   "auto"   ||   N: N character cells   ||   Npx: N pixels   ||   N%: N percent of terminal width/height
+		wdgt.Block.ANSIString = fmt.Sprintf("\033[%d;%dH%s", imageDimensions.Min.Y, imageDimensions.Min.X, iterm2String)
+
+		return nil
+	}
+	skipIterm2:
+
+	return errors.New("no method applied for ANSI drawing")
+}

widgets/exp/drawer_kitty.go

@@ -0,0 +1,102 @@
+// <Copyright> 2019 Simon Robin Lehn. All rights reserved.
+// Use of this source code is governed by a MIT license that can
+// be found in the LICENSE file.
+
+package exp
+
+import (
+	"fmt"
+	"errors"
+	"bytes"
+	"encoding/base64"
+	"image/png"
+
+	. "github.com/gizak/termui/v3"
+	"github.com/gizak/termui/v3/widgets"
+)
+
+const (
+	kittyLimit = 4096
+)
+
+var (
+	// TODO: for numbering of ids
+	kittyImageCount int
+)
+
+func init() {
+	widgets.RegisterDrawer(
+		"kitty",
+		widgets.Drawer{
+			Remote:         true,
+			IsEscapeString: true,
+			Available:      func() bool {return isKitty},
+			Draw:           drawKitty,
+		},
+	)
+}
+
+func drawKitty(wdgt *widgets.Image, buf *Buffer) (err error) {
+	if !isKitty {
+		return errors.New("method not supported for this terminal type")
+	}
+
+	wdgt.Block.Draw(buf)
+
+	//  TODO: FIX THIS
+	termWidth, termHeight := getTermSizeInChars(true)
+	var _ = termWidth
+	/*
+	if termWidth == 0 || termHeight == 0 {
+		return errors.New("could not query terminal dimensions")
+	}
+	*/
+
+	img, changed, err := resizeImage(wdgt, buf)
+	if !changed || err != nil {
+		return err
+	}
+
+	var imgHeight int
+	imageDimensions := wdgt.GetVisibleArea()
+	if wdgt.Inner.Max.Y < termHeight {
+		imgHeight = wdgt.Inner.Dy()
+	} else {
+		imgHeight = termHeight-1
+	}
+	imgHeight = wdgt.Inner.Dy()   // TODO: REMOVE THIS CRUTCH
+
+	// https://sw.kovidgoyal.net/kitty/graphics-protocol.html#remote-client
+	// https://sw.kovidgoyal.net/kitty/graphics-protocol.html#png-data
+	// https://sw.kovidgoyal.net/kitty/graphics-protocol.html#controlling-displayed-image-layout
+	bytBuf := new(bytes.Buffer)
+	if err = png.Encode(bytBuf, img); err != nil {
+		return err
+	}
+	imgBase64 := base64.StdEncoding.EncodeToString(bytBuf.Bytes())
+	lenImgB64 := len([]byte(imgBase64))
+	// a=T           action
+	// t=d           payload is (base64 encoded) data itself not a file location
+	// f=100         format: 100 = PNG payload
+	// o=z           data compression
+	// X=...,Y=,,,   Upper left image corner in cell coordinates (starting with 1, 1)
+	// c=...,r=...   image size in cell columns and rows
+	// w=...,h=...   width & height (in pixels) of the image area to display   // TODO: Use this to let Kitty handle cropping!
+	// z=0           z-index vertical stacking order of the image
+	// m=[01]        0 last escape code chunk - 1 for all except the last
+	var kittyString string
+	var zIndex = 2   // draw over text
+	settings := fmt.Sprintf("a=T,t=d,f=100,X=%d,Y=%d,c=%d,r=%d,z=%d,", imageDimensions.Min.X, imageDimensions.Min.Y, wdgt.Inner.Dx(), imgHeight, zIndex)
+	i := 0
+	for ; i < (lenImgB64-1)/kittyLimit; i++ {
+		kittyString += wrap(fmt.Sprintf("\033_G%sm=1;%s\033\\", settings, imgBase64[i*kittyLimit:(i+1)*kittyLimit]))
+		settings = ""
+	}
+	kittyString += wrap(fmt.Sprintf("\033_G%sm=0;%s\033\\", settings, imgBase64[i*kittyLimit:lenImgB64]))
+
+	wdgt.Block.ANSIString = fmt.Sprintf("\033[%d;%dH%s", imageDimensions.Min.Y, imageDimensions.Min.X, kittyString)
+	return nil
+}
+
+// TODO:
+// store images with ids in Kitty

widgets/exp/drawer_sixel.go

@@ -0,0 +1,63 @@
+// <Copyright> 2018,2019 Simon Robin Lehn. All rights reserved.
+// Use of this source code is governed by a MIT license that can
+// be found in the LICENSE file.
+
+package exp
+
+import (
+	"fmt"
+	"bytes"
+	"errors"
+
+	"github.com/mattn/go-sixel"
+
+	. "github.com/gizak/termui/v3"
+	"github.com/gizak/termui/v3/widgets"
+)
+
+
+func init() {
+	widgets.RegisterDrawer(
+		"sixel",
+		widgets.Drawer{
+			Remote:         true,
+			IsEscapeString: true,
+			Available:      func() bool {return sixelCapable},
+			Draw:           drawSixel,
+		},
+	)
+}
+
+func drawSixel(wdgt *widgets.Image, buf *Buffer) (err error) {
+	wdgt.Block.Draw(buf)
+
+	img, changed, err := resizeImage(wdgt, buf)
+	if !changed || err != nil {
+		return err
+	}
+
+	// sixel
+	// https://vt100.net/docs/vt3xx-gp/chapter14.html
+	if sixelCapable {
+		byteBuf := new(bytes.Buffer)
+		enc := sixel.NewEncoder(byteBuf)
+		enc.Dither = true
+		if err := enc.Encode(img); err != nil {
+			return err
+		}
+		sixelString := wrap("\033[?8452h" + byteBuf.String())
+		// position where the image should appear (upper left corner) + sixel
+		// https://github.com/mintty/mintty/wiki/CtrlSeqs#sixel-graphics-end-position
+		// "\033[?8452h" sets the cursor next right to the bottom of the image instead of below
+		// this prevents vertical scrolling when the image fills the last line.
+		// horizontal scrolling because of this did not happen in my test cases.
+		// "\033[?80l" disables sixel scrolling if it isn't already.
+		wdgt.Block.ANSIString = fmt.Sprintf("\033[%d;%dH%s", wdgt.Inner.Min.Y + 1, wdgt.Inner.Min.X + 1, sixelString)
+		// test string "HI"
+		// wdgt.Block.ANSIString = fmt.Sprintf("\033[%d;%dH\033[?8452h%s", wdgt.Inner.Min.Y+1, wdgt.Inner.Min.X+1, "\033Pq#0;2;0;0;0#1;2;100;100;0#2;2;0;100;0#1~~@@vv@@~~@@~~$#2??}}GG}}??}}??-#1!14@\033\\")
+
+		return nil
+	}
+
+	return errors.New("no method applied for ANSI drawing")
+}

widgets/exp/drawer_urxvt.go

@@ -0,0 +1,90 @@
+// <Copyright> 2019 Simon Robin Lehn. All rights reserved.
+// Use of this source code is governed by a MIT license that can
+// be found in the LICENSE file.
+
+package exp
+
+import (
+	"fmt"
+	"bytes"
+	"errors"
+	"image/png"
+	"crypto/md5"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+
+	. "github.com/gizak/termui/v3"
+	"github.com/gizak/termui/v3/widgets"
+)
+
+
+var (
+	tempdir string
+)
+
+func init() {
+	widgets.RegisterDrawer(
+		"urxvt",
+		widgets.Drawer{
+			Remote:         false,
+			IsEscapeString: true,
+			Available:      func() bool {return isUrxvt},
+			Draw:           drawUrxvt,
+		},
+	)
+}
+
+func drawUrxvt(wdgt *widgets.Image, buf *Buffer) (err error) {
+	if !isUrxvt {
+		return errors.New("method not supported for this terminal type")
+	}
+
+	// wdgt.Block.Draw(buf)
+
+	var widthPercentage, heightPercentage, CenterPosXPercentage, CenterPosYPercentage int
+	termWidth, termHeight := getTermSizeInChars(true)
+	if termWidth == 0 || termHeight == 0 {
+		return errors.New("could not query terminal dimensions")
+	}
+
+	widthPercentage  = (100*wdgt.Inner.Dx())/termWidth
+	heightPercentage = (100*wdgt.Inner.Dy())/termHeight
+	maxX := wdgt.Inner.Max.X
+	maxY := wdgt.Inner.Max.Y
+	if termWidth < maxX {
+		maxX = termWidth
+	}
+	if termHeight < maxY {
+		maxY = termHeight
+	}
+	CenterPosXPercentage = 50*(wdgt.Inner.Min.X+maxX)/termWidth
+	CenterPosYPercentage = 50*(wdgt.Inner.Min.Y+maxY)/termHeight
+
+	img, changed, err := resizeImage(wdgt, buf)
+	if !changed || err != nil {
+		return err
+	}
+
+	bytBuf := new(bytes.Buffer)
+	if err = png.Encode(bytBuf, img); err != nil {
+		return errors.New("image encoding failed")
+	}
+
+	if fi, err := os.Stat(tempdir); err != nil || !fi.IsDir() {
+		if tempdir, err = ioutil.TempDir("", "termui."); err != nil {
+			return err
+		}
+	}
+
+	// defer os.RemoveAll(dir) // clean up
+
+	filename := filepath.Join(tempdir, fmt.Sprintf("urxvt-%x", md5.Sum(bytBuf.Bytes())) + ".png")
+	if err := ioutil.WriteFile(filename, bytBuf.Bytes(), 0644); err != nil {
+		return err
+	}
+
+	// "op=keep-aspect" maintains the image aspect ratio when scaling
+	wdgt.Block.ANSIString = wrap(fmt.Sprintf("\033]20;%s;%dx%d+%d+%d:op=keep-aspect\a", filename, widthPercentage, heightPercentage, CenterPosXPercentage, CenterPosYPercentage))
+	return nil
+}

widgets/exp/image.go

@@ -0,0 +1,107 @@
+// <Copyright> 2018,2019 Simon Robin Lehn. All rights reserved.
+// Use of this source code is governed by a MIT license that can
+// be found in the LICENSE file.
+
+package exp
+
+import (
+	"fmt"
+	"errors"
+	"image"
+
+	"github.com/disintegration/imaging"
+
+	. "github.com/gizak/termui/v3"
+	"github.com/gizak/termui/v3/widgets"
+)
+
+var (
+	charBoxWidthInPixels, charBoxHeightInPixels   float64
+	charBoxWidthColumns,  charBoxHeightRows       int
+)
+
+
+func resizeImage(wdgt *widgets.Image, buf *Buffer) (img image.Image, changed bool, err error) {
+	img = wdgt.Image
+	// img = image.NRGBA{}
+
+	// get dimensions //
+	// terminal size measured in cells
+	imageWidthInColumns := wdgt.Inner.Dx()
+	imageHeightInRows   := wdgt.Inner.Dy()
+
+	// terminal size in cells and pixels and calculated terminal character box size in pixels
+	var termWidthInColumns, termHeightInRows int
+	var charBoxWidthInPixelsTemp, charBoxHeightInPixelsTemp float64
+	termWidthInColumns, termHeightInRows, _, _, charBoxWidthInPixelsTemp, charBoxHeightInPixelsTemp, err = getTermSize()
+	if err != nil {
+		return img, true, err
+	}
+	// update if value is more precise
+	if termWidthInColumns > charBoxWidthColumns {
+		charBoxWidthInPixels = charBoxWidthInPixelsTemp
+	}
+	if termHeightInRows > charBoxHeightRows {
+		charBoxHeightInPixels = charBoxHeightInPixelsTemp
+	}
+if isTmux {charBoxWidthInPixels, charBoxHeightInPixels = 10, 19}   // mlterm settings (temporary)
+
+	// calculate image size in pixels
+	// subtract 1 pixel for small deviations from char box size (float64)
+	imageWidthInPixels  := int(float64(imageWidthInColumns) * charBoxWidthInPixels)  - 1
+	imageHeightInPixels := int(float64(imageHeightInRows)   * charBoxHeightInPixels) - 1
+	if imageWidthInPixels == 0 || imageHeightInPixels == 0 {
+		return img, true, errors.New("could not calculate the image size in pixels")
+	}
+
+	// handle only partially displayed image
+	// otherwise we get scrolling
+	var needsCropX, needsCropY bool
+	var imgCroppedWidth, imgCroppedHeight int
+	imgCroppedWidth  = imageWidthInPixels
+	imgCroppedHeight = imageHeightInPixels
+	if wdgt.Max.Y >= int(termHeightInRows) {
+		var scrollExtraRows int
+		// remove last 2 rows for xterm when cropped vertically to prevent scrolling
+		if isXterm {
+			scrollExtraRows = 2
+		}
+		/*
+		if isKitty {
+			scrollExtraRows = 1
+		}
+		*/
+		// subtract 1 pixel for small deviations from char box size (float64)
+		imgCroppedHeight = int(float64(int(termHeightInRows) - wdgt.Inner.Min.Y - scrollExtraRows) * charBoxHeightInPixels) - 1
+		needsCropY = true
+	}
+	if wdgt.Max.X >= int(termWidthInColumns) {
+		var scrollExtraColumns int
+		imgCroppedWidth = int(float64(int(termWidthInColumns) - wdgt.Inner.Min.X - scrollExtraColumns) * charBoxWidthInPixels) - 1
+		needsCropX = true
+	}
+
+	lastImageDimensions := wdgt.GetVisibleArea()
+	// this is meant for comparison and for positioning in the ANSI string
+	// the Min values are in cells while the Max values are in pixels
+	// imageDimensions := image.Rectangle{Min: image.Point{X: 0, Y: 0}, Max: image.Point{X: imgCroppedWidth, Y: imgCroppedHeight}}
+	imageDimensions := image.Rectangle{Min: image.Point{X: wdgt.Inner.Min.X + 1, Y: wdgt.Inner.Min.Y + 1}, Max: image.Point{X: imgCroppedWidth, Y: imgCroppedHeight}}
+	wdgt.SetVisibleArea(imageDimensions)
+	// print saved ANSI string if image size and position didn't change
+	if imageDimensions.Min.X == lastImageDimensions.Min.X && imageDimensions.Min.Y == lastImageDimensions.Min.Y && imageDimensions.Max.X == lastImageDimensions.Max.X && imageDimensions.Max.Y == lastImageDimensions.Max.Y {
+		// reuse last encoded image because of unchanged image dimensions
+		return img, false, nil
+	}
+	lastImageDimensions = imageDimensions
+
+	// resize and crop the image //
+	img = imaging.Resize(wdgt.Image, imageWidthInPixels, imageHeightInPixels, imaging.Lanczos)
+	if needsCropX || needsCropY {
+		img = imaging.Crop(img, image.Rectangle{Min: image.Point{X: 0, Y: 0}, Max: image.Point{X: imgCroppedWidth, Y: imgCroppedHeight}})
+	}
+	if img.Bounds().Dx() == 0 || img.Bounds().Dy() == 0 {
+		return img, true, fmt.Errorf("image size in pixels is 0")
+	}
+	
+	return img, true, err
+}

widgets/exp/multiplexer.go

@@ -0,0 +1,28 @@
+// <Copyright> 2019 Simon Robin Lehn. All rights reserved.
+// Use of this source code is governed by a MIT license that can
+// be found in the LICENSE file.
+
+package exp
+
+import (
+	"strings"
+)
+
+func wrap(s string) string {
+	if !isMuxed {
+		return s
+	}
+	if isTmux {
+		return tmuxWrap(s)
+	}
+	return s
+}
+
+func tmuxWrap(s string) string {
+	return "\033Ptmux;" + strings.Replace(s, "\033", "\033\033", -1) + "\033\\"
+}
+
+/*
+// https://savannah.gnu.org/bugs/index.php?56063
+func screenWrap(s string) string {}
+*/

widgets/exp/terminal_query.go

@@ -0,0 +1,177 @@
+// <Copyright> 2018,2019 Simon Robin Lehn. All rights reserved.
+// Use of this source code is governed by a MIT license that can
+// be found in the LICENSE file.
+
+package exp
+
+import (
+	"fmt"
+	"strconv"
+	"time"
+
+	"github.com/mattn/go-tty"
+)
+
+func getTermSize() (termWidthInColumns, termHeightInRows, termWidthInPixels, termHeightInPixels int, charBoxWidthInPixels, charBoxHeightInPixels float64, err error) {
+	// this uses a combination of TIOCGWINSZ and \033[14t , \033[18t
+	// the syscall to TIOCGWINSZ only works locally
+
+	var cx, cy, px, py int
+	err = nil
+
+	t, err := tty.Open()
+	defer t.Close()
+
+	cx, cy, px, py, err = t.SizePixel()
+	// if isMuxed {
+	if false {   // temporary
+		// in case of split view it is better to query from the same source
+		/*if cx <= 0 || cy <= 0 || px <= 0 || py <= 0 {
+			cx, cy = getTermSizeInChars(true)
+			px, py = getTermSizeInPixels(true)
+			if cx <= 0 || cy <= 0 || px <= 0 || py <= 0 {
+				cx, cy = getTermSizeInChars(false)
+				px, py = getTermSizeInPixels(false)
+				if cx <= 0 || cy <= 0 || px <= 0 || py <= 0 {
+					return
+				}	
+			}	
+		}*/	
+	} else if err == nil {
+		if cx > 0 && cy > 0 {
+			if px <= 0 || py <= 0 {
+				px, py = getTermSizeInPixels(true)
+			}
+		} else {
+			if cx, cy = getTermSizeInChars(true); cx != 0 && cy != 0 {
+				if px <= 0 || py <= 0 {
+					px, py = getTermSizeInPixels(true)
+				}
+			} else {
+				return
+			}
+		}
+	}
+
+	termWidthInColumns    = cx
+	termHeightInRows      = cy
+	termWidthInPixels     = px
+	termHeightInPixels    = py
+	charBoxWidthInPixels  = float64(px) / float64(cx)
+	charBoxHeightInPixels = float64(py) / float64(cy)
+	return
+}
+
+func getTermSizeInChars(needsWrap bool) (x, y int) {
+	// query terminal size in character boxes
+	// answer: <termHeightInRows>;<termWidthInColumns>t
+	s := "\033[18t"
+	if needsWrap {
+		s = wrap(s)
+	}
+	q := queryTerm(s)
+	if len(q) != 3 {
+		return
+	}
+
+	if yy, err := strconv.Atoi(string(q[1])); err == nil {
+		if xx, err := strconv.Atoi(string(q[2])); err == nil {
+			x = xx
+			y = yy
+		} else {
+			return
+		}
+	} else {
+		return
+	}
+
+	return
+}
+
+func getTermSizeInPixels(needsWrap bool) (x, y int) {
+	// query terminal size in pixels
+	// answer: <termHeightInPixels>;<termWidthInPixels>t
+	s := "\033[14t"
+	if needsWrap {
+		s = wrap(s)
+	}
+	q := queryTerm(s)
+
+	if len(q) != 3 {
+		return
+	}
+
+	if yy, err := strconv.Atoi(string(q[1])); err == nil {
+		if xx, err := strconv.Atoi(string(q[2])); err == nil {
+			x = xx
+			y = yy
+		} else {
+			return
+		}
+	} else {
+		return
+	}
+
+	return
+}
+
+func queryTerm(qs string) (ret [][]rune) {
+	// temporary fix for xterm - not completely sure if still needed
+	// otherwise TUI wouldn't react to any further events
+	// resizing still works though
+	if isXterm && qs != "\033[0c" && qs != wrap("\033[0c") {
+		return
+	}
+
+	var b []rune
+
+	t, err := tty.Open()
+	if err != nil {
+		return
+	}
+
+	ch := make(chan bool, 1)
+
+	go func() {
+		defer t.Close()
+		// query terminal
+		fmt.Printf(qs)
+
+		for {
+			r, err := t.ReadRune()
+			if err != nil {
+				return
+			}
+			// handle key event
+			switch r {
+			case 'c', 't':
+				ret = append(ret, b)
+				goto afterLoop
+			case '?', ';':
+				ret = append(ret, b)
+				b = []rune{}
+			default:
+				b = append(b, r)
+			}
+		}
+	afterLoop:
+		ch <- true
+	}()
+
+	var timer *time.Timer
+	if isTmux {
+		// tmux needs a bit more time
+		timer = time.NewTimer(50000 * time.Microsecond)
+	} else {
+		// on my system the terminals mlterm, xterm need at least around 100 microseconds
+		timer = time.NewTimer(500 * time.Microsecond)
+	}
+	defer timer.Stop()
+
+	select {
+	case <-ch:
+		defer close(ch)
+	case <-timer.C:
+	}
+	return
+}

widgets/exp/terminal_scan.go

@@ -0,0 +1,51 @@
+// <Copyright> 2018,2019 Simon Robin Lehn. All rights reserved.
+// Use of this source code is governed by a MIT license that can
+// be found in the LICENSE file.
+
+package exp
+
+import (
+	"os"
+	"strings"
+)
+
+var (
+	sixelCapable, isXterm, isMlterm, isMintty, isIterm2, isUrxvt, isAlacritty, isYaft, isKitty, isMacTerm, isTmux, isScreen, isMuxed   bool
+)
+
+func scanTerminal() {
+	if len(os.Getenv("XTERM_VERSION")) > 0                                          { isXterm     = true } else { isXterm     = false }
+	if os.Getenv("TERM_PROGRAM") == "iTerm.app"                                     { isIterm2    = true } else { isIterm2    = false }   // https://superuser.com/a/683971
+	if os.Getenv("TERM_PROGRAM") == "MacTerm"                                       { isMacTerm   = true } else { isMacTerm   = false }   // https://github.com/kmgrant/macterm/issues/3#issuecomment-458387953
+	if strings.HasPrefix(os.Getenv("TERM"), "rxvt-unicode")                         { isUrxvt     = true } else { isUrxvt     = false }
+	if os.Getenv("TERM") == "xterm-kitty" ||len(os.Getenv("KITTY_WINDOW_ID")) > 0   { isKitty     = true } else { isKitty     = false }
+	if len(os.Getenv("MLTERM")) > 0                                                 { isMlterm    = true } else { isMlterm    = false }
+	if len(os.Getenv("MINTTY_SHORTCUT")) > 0                                        { isMintty    = true } else { isMintty    = false }
+	if len(os.Getenv("ALACRITTY_LOG")) > 0                                          { isAlacritty = true } else { isAlacritty = false }
+	if os.Getenv("TERM") == "yaft-256color"                                         { isYaft      = true } else { isYaft      = false }   // https://github.com/uobikiemukot/yaft/blob/21b69124a2907ad6ede8f45ca96c390615e3dc0c/conf.h#L26
+	if  strings.HasPrefix(os.Getenv("TERM"), "screen") && len(os.Getenv("STY")) > 0 { isScreen    = true } else { isScreen    = false }
+	if (strings.HasPrefix(os.Getenv("TERM"), "screen") || strings.HasPrefix(os.Getenv("TERM"), "tmux")) &&
+	   len(os.Getenv("TMUX")) > 0 || len(os.Getenv("TMUX_PANE")) > 0                { isTmux      = true } else { isTmux      = false }
+	if isTmux || isScreen                                                           { isMuxed     = true } else { isMuxed     = false }
+
+	if isYaft {
+		sixelCapable = true
+	} else {
+		sixelCapable = false
+	}
+	// example query: "\033[0c"
+	// possible answer from the terminal (here xterm): "\033[[?63;1;2;4;6;9;15;22c", vte(?): ...62,9;c
+	// the "4" signals that the terminal is capable of sixel
+	// conhost.exe knows this sequence.
+	if !sixelCapable {
+		termCapabilities := queryTerm(wrap("\033[0c"))
+		for i, cap := range termCapabilities {
+			if i == 0 || i == len(termCapabilities) - 1 {
+				continue
+			}
+			if string(cap) == `4` {
+				sixelCapable = true
+			}
+		}
+	}
+}

widgets/image.go

@@ -7,39 +7,107 @@ package widgets
 import (
 	"image"
 	"image/color"
+	"sync"
+	"sync/atomic"
 
 	. "github.com/gizak/termui/v3"
 )
 
+type Drawer struct {
+	Remote         bool   // if the drawer can be used for remote terminals
+	IsEscapeString bool
+	Available      func() (bool)
+	Draw           func(*Image, *Buffer) (error)
+}
+
+var (
+	drawersMu     sync.Mutex
+	atomicDrawers atomic.Value
+)
+
+// from https://golang.org/src/image/format.go?s=1069:1193#L31
+func RegisterDrawer(nameNew string, drawerNew Drawer) {
+	drawersMu.Lock()
+	// drawers, _ := atomicDrawers.Load().([]Drawer)
+	// atomicDrawers.Store(append(drawers, dr))
+	drawers, _ := atomicDrawers.Load().(map[string]Drawer)
+	drawersNew := make(map[string]Drawer)
+	for name, drawer := range drawers {
+		drawersNew[name] = drawer
+	}
+	drawersNew[nameNew] = drawerNew
+	atomicDrawers.Store(drawersNew)
+	drawersMu.Unlock()
+}
+
+func GetDrawers() map[string]Drawer {
+	if drawers, ok := atomicDrawers.Load().(map[string]Drawer); ok {
+		return drawers
+	}
+	return map[string]Drawer{}
+}
+
+func init() {
+	RegisterDrawer(
+		"block",
+		Drawer{
+			Remote:         true,
+			IsEscapeString: false,
+			Available:      func() bool {return true},
+			Draw:           drawBlocks,
+		},
+	)
+}
+
 type Image struct {
 	Block
-	Image               image.Image
+	Image                   image.Image
-	Monochrome          bool
+	Monochrome              bool
-	MonochromeThreshold uint8
+	MonochromeThreshold     uint8
-	MonochromeInvert    bool
+	MonochromeInvert        bool
+	visibleSubImagePixels   image.Rectangle
 }
 
 func NewImage(img image.Image) *Image {
 	return &Image{
-		Block:               *NewBlock(),
+		Block:                 *NewBlock(),
-		MonochromeThreshold: 128,
+		MonochromeThreshold:   128,
-		Image:               img,
+		Image:                 img,
+		visibleSubImagePixels: image.Rectangle{},
 	}
 }
 
 func (self *Image) Draw(buf *Buffer) {
-	self.Block.Draw(buf)
+	drawers := GetDrawers()
 
-	if self.Image == nil {
+	// fall back - draw with box characters atomicDrawers.Load().(map[string]Drawer)]["blocks"]
+	// possible enhancement: make use of further box characters like chafa:
+	// https://hpjansson.org/chafa/
+	// https://github.com/hpjansson/chafa/
+	if drbl, ok := drawers["block"]; ok {
+		drbl.Draw(self, buf)
+	}
+
+	for name, dr := range drawers {
+		if name != "block" && dr.Available() {
+			dr.Draw(self, buf)
+		}
+	}
+}
+
+func drawBlocks(img *Image, buf *Buffer) (err error) {
+	img.Block.Draw(buf)
+
+	if img.Image == nil {
 		return
 	}
 
-	bufWidth := self.Inner.Dx()
+	bufWidth := img.Inner.Dx()
-	bufHeight := self.Inner.Dy()
+	bufHeight := img.Inner.Dy()
-	imageWidth := self.Image.Bounds().Dx()
+	imageWidth := img.Image.Bounds().Dx()
-	imageHeight := self.Image.Bounds().Dy()
+	imageHeight := img.Image.Bounds().Dy()
 
-	if self.Monochrome {
+	if img.Monochrome {
 		if bufWidth > imageWidth/2 {
 			bufWidth = imageWidth / 2
 		}
@@ -48,33 +116,33 @@ func (self *Image) Draw(buf *Buffer) {
 		}
 		for bx := 0; bx < bufWidth; bx++ {
 			for by := 0; by < bufHeight; by++ {
-				ul := self.colorAverage(
+				ul := img.colorAverage(
 					2*bx*imageWidth/bufWidth/2,
 					(2*bx+1)*imageWidth/bufWidth/2,
 					2*by*imageHeight/bufHeight/2,
 					(2*by+1)*imageHeight/bufHeight/2,
 				)
-				ur := self.colorAverage(
+				ur := img.colorAverage(
 					(2*bx+1)*imageWidth/bufWidth/2,
 					(2*bx+2)*imageWidth/bufWidth/2,
 					2*by*imageHeight/bufHeight/2,
 					(2*by+1)*imageHeight/bufHeight/2,
 				)
-				ll := self.colorAverage(
+				ll := img.colorAverage(
 					2*bx*imageWidth/bufWidth/2,
 					(2*bx+1)*imageWidth/bufWidth/2,
 					(2*by+1)*imageHeight/bufHeight/2,
 					(2*by+2)*imageHeight/bufHeight/2,
 				)
-				lr := self.colorAverage(
+				lr := img.colorAverage(
 					(2*bx+1)*imageWidth/bufWidth/2,
 					(2*bx+2)*imageWidth/bufWidth/2,
 					(2*by+1)*imageHeight/bufHeight/2,
 					(2*by+2)*imageHeight/bufHeight/2,
 				)
 				buf.SetCell(
-					NewCell(blocksChar(ul, ur, ll, lr, self.MonochromeThreshold, self.MonochromeInvert)),
+					NewCell(blocksChar(ul, ur, ll, lr, img.MonochromeThreshold, img.MonochromeInvert)),
-					image.Pt(self.Inner.Min.X+bx, self.Inner.Min.Y+by),
+					image.Pt(img.Inner.Min.X+bx, img.Inner.Min.Y+by),
 				)
 			}
 		}
@@ -87,7 +155,7 @@ func (self *Image) Draw(buf *Buffer) {
 		}
 		for bx := 0; bx < bufWidth; bx++ {
 			for by := 0; by < bufHeight; by++ {
-				c := self.colorAverage(
+				c := img.colorAverage(
 					bx*imageWidth/bufWidth,
 					(bx+1)*imageWidth/bufWidth,
 					by*imageHeight/bufHeight,
@@ -95,11 +163,22 @@ func (self *Image) Draw(buf *Buffer) {
 				)
 				buf.SetCell(
 					NewCell(c.ch(), NewStyle(c.fgColor(), ColorBlack)),
-					image.Pt(self.Inner.Min.X+bx, self.Inner.Min.Y+by),
+					image.Pt(img.Inner.Min.X+bx, img.Inner.Min.Y+by),
 				)
 			}
 		}
 	}
+	return
+}
+
+// measured in pixels
+func (self *Image) SetVisibleArea(area image.Rectangle) {
+	self.visibleSubImagePixels = area
+}
+
+// measured in pixels
+func (self *Image) GetVisibleArea() image.Rectangle {
+	return self.visibleSubImagePixels
 }
 
 func (self *Image) colorAverage(x0, x1, y0, y1 int) colorAverager {