sixel preview (gokcehan#1211)

* Sixel patch (gokcehan#1)

* new struct type sixel

* add sixel detection logic in printReg

* new ShowSixels that prints sixels to the screen

* placeholder function UnshowSixels

* run `ui.ShowSixels` after `ui.screen.Sync`

* fix sixel placed on wrong coordinates

* change sixel termination sequence to prevent other escape sequence being run inside it

* process multi-line sixel sequence

* fixed bug where string before sixel image is not printed

* add sixelDimPx and pxToCells

* add getTermPixels for unix

* remove unused method UnshowSixels

* fix: remove unneeded ShowSixels

* add new fields sixel.wPx,hPx and reg.sixels

* modify sixel processing logic

detecting sixels in preview script now fills corresponding area with braille blank `\u2800` and saves sixel to reg.sixels

* modify sixel processing logic

printReg doesn't process sixels directly anymore

* reset sixels buffer at the start of `draw`

* rename `ui.ShowSixels` to `showSixels`

* add constants `gSixelBegin` and `gSixelTerminate`

* add check to prevent arbitrary escape code being passed to stdin

* fix cursor out of place in command line mode

* fix bug where sixel in drawn at old location after horizontal resize

* add ui.wPx and ui.hPx

* buffer sixel sequences before printing

* add check for valid terminal size(px) before previewing sixel

* clean up

* placeholder function getTermPixels for windows

* function sixelDimPx now considers image size given in the optional raster attributes field

* change sixel image alignment to emulate behavior of a terminal
- images used to always draw on a new line
- images is now placed where it starts:
```
printf 'abc <sixel sequence> xyz'
```
would result in:
```
abc +------+
    | img  |
    | here |
    +------+
xyz
```

old behavior:
```
abc
+------+
| img  |
| here |
+------+
xyz
```

* fix bug where raster attributes are wrongly parsed in sixelDimPx

* prevent drawing sixels while menu is active

* introduce sixelScreen struct and refactor screen width,height in px to use new struct

* fix prevent nested sixel sequences

* fix bug where rejected sixels cause indexing error

* add "alternating filler" to trick tcell into redrawing when switching between different images

* fix filler string wrongly indented

* add comment

* replace pxToCells() with sixelScreen.pxToCells()

* add trim sixel height during preview

* add tests for trimSixelHeight

* prevent sixel redrawing during input prompts

* change sixel filler to braille space

* clean up

* use strings.Index instead of regex for simple search

* fix comment

* refactor: remove nested if-block

* refactor: move sixel related stuff into sixel.go

* remove unused function

* allow long lines from previewer

* rework preview to accept only single-line sixels

- multi-line support removed for simplicity in the code base

* add new option `sixel`

* add eval logic and completion of `sixel` option

* doc: new option 'sixel'

* refactor: use newSixelScreen() for init

* fix bug where image is not always cleared

* refactor: separate sixel tests

* improved error handling

* rename & comments for clarity

* refactor: renderPreviewLine should not use gOpts

* rename for clarity

* fix: filler style changed more than needed

The filler style now only changes when the file in preview is changed

* rename

* fix: forgot to rename this

* increase max line size

* remove unneeded reassignment

* fix position of multiple sixel on same line

* refactor: extract code into function

* update docs

* reorder variable

* remove unneeded var

* avoid unneeded ioctl calls

* fixup! fix typo

* rework/simplify previewing sixels

Remove support for multiple sixels on the same line, and the line must start with 'ESC P' to be considered a sixel.

* separate sixel detection logic from text scanning

* rework: stricter sixel validation and remove trimming

* revert unneeded changes

* strip validation logic

* refactor: use singular sixel instead of slice

multiple sixel preview is no longer supported

* fix: bug where first 2 char of non-sixel is missing

* docs: fix wrong option type

* set sixelScreen.wpx, hpx to 0 on error

* remove terminal px size

* fix: bug where quitting might leave terminal in bold

cleanup

* update docs

* remove unneeded sixel type

* cleanup unused func argument

* cleanup unneeded function

* refactor: more readable

Co-authored-by: Joe Lim <50560759+joelim-work@users.noreply.github.com>

* cleanup unneeded var

* cleanup unneeded constructor

* cleanup unused func arg

---------

Co-authored-by: Joe Lim <50560759+joelim-work@users.noreply.github.com>

complete.go

@@ -179,6 +179,9 @@ var (
 		"reverse!",
 		"ruler",
 		"preserve",
+		"sixel",
+		"nosixel",
+		"sixel!",
 		"smartcase",
 		"nosmartcase",
 		"smartcase!",

doc.go

@@ -164,6 +164,7 @@ The following options can be used to customize the behavior of lf:
 	shell            string    (default 'sh' for Unix and 'cmd' for Windows)
 	shellflag        string    (default '-c' for Unix and '/c' for Windows)
 	shellopts        []string  (default '')
+	sixel            bool      (default false)
 	smartcase        bool      (default true)
 	smartdia         bool      (default false)
 	sortby           string    (default 'natural')
@@ -910,6 +911,10 @@ Command line flag used to pass shell commands.
 
 List of shell options to pass to the shell executable.
 
+	sixel          bool      (default false)
+
+Render sixel images in preview.
+
 	smartcase      bool      (default true)
 
 Override 'ignorecase' option when the pattern contains an uppercase character.

eval.go

@@ -891,6 +891,27 @@ func (e *setExpr) eval(app *app, args []string) {
 			return
 		}
 		gOpts.wrapscroll = !gOpts.wrapscroll
+	case "sixel":
+		if e.val == "" || e.val == "true" {
+			gOpts.sixel = true
+		} else if e.val == "false" {
+			gOpts.sixel = false
+		} else {
+			app.ui.echoerr("sixel: value should be empty, 'true', or 'false'")
+			return
+		}
+	case "nosixel":
+		if e.val != "" {
+			app.ui.echoerrf("nosixel: unexpected value: %s", e.val)
+			return
+		}
+		gOpts.sixel = false
+	case "sixel!":
+		if e.val != "" {
+			app.ui.echoerrf("sixel!: unexpected value: %s", e.val)
+			return
+		}
+		gOpts.sixel = !gOpts.sixel
 	default:
 		// any key with the prefix user_ is accepted as a user defined option
 		if strings.HasPrefix(e.opt, "user_") {

lf.1

@@ -183,6 +183,7 @@ The following options can be used to customize the behavior of lf:
     shell            string    (default 'sh' for Unix and 'cmd' for Windows)
     shellflag        string    (default '-c' for Unix and '/c' for Windows)
     shellopts        []string  (default '')
+    sixel            bool      (default false)
     smartcase        bool      (default true)
     smartdia         bool      (default false)
     sortby           string    (default 'natural')
@@ -1083,6 +1084,12 @@ Command line flag used to pass shell commands.
 .PP
 List of shell options to pass to the shell executable.
 .PP
+.EX
+    sixel          bool      (default false)
+.EE
+.PP
+Render sixel images in preview.
+.PP
 .EX
     smartcase      bool      (default true)
 .EE

nav.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"bufio"
+	"bytes"
 	"errors"
 	"fmt"
 	"io"
@@ -847,6 +848,22 @@ func (nav *nav) preview(path string, win *win) {
 		reader = f
 	}
 
+	prefix := make([]byte, 2)
+	if gOpts.sixel {
+		_, err := reader.Read(prefix)
+		reader = io.MultiReader(bytes.NewReader(prefix), reader)
+
+		if err == nil && string(prefix) == gSixelBegin {
+			b, err := io.ReadAll(reader)
+			if err != nil {
+				log.Printf("loading sixel: %s", err)
+			}
+			str := string(b)
+			reg.sixel = &str
+			return
+		}
+	}
+
 	buf := bufio.NewScanner(reader)
 
 	for i := 0; i < win.h && buf.Scan(); i++ {

opts.go

@@ -49,6 +49,7 @@ var gOpts struct {
 	mouse            bool
 	number           bool
 	preview          bool
+	sixel            bool
 	relativenumber   bool
 	smartcase        bool
 	smartdia         bool
@@ -113,6 +114,7 @@ func init() {
 	gOpts.mouse = false
 	gOpts.number = false
 	gOpts.preview = true
+	gOpts.sixel = false
 	gOpts.relativenumber = false
 	gOpts.smartcase = true
 	gOpts.smartdia = false

sixel.go

@@ -0,0 +1,61 @@
+package main
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/gdamore/tcell/v2"
+)
+
+const (
+	gSixelBegin  = "\033P"
+	gSixelFiller = '\u2800'
+)
+
+type sixelScreen struct {
+	xprev, yprev int
+	sixel        *string
+	altFill      bool
+	lastFile     string // TODO maybe use hash of sixels instead to flip altFill
+}
+
+func (sxs *sixelScreen) fillerStyle(filePath string) tcell.Style {
+	if sxs.lastFile != filePath {
+		sxs.altFill = !sxs.altFill
+	}
+
+	if sxs.altFill {
+		return tcell.StyleDefault.Bold(true)
+	}
+	return tcell.StyleDefault
+}
+
+func (sxs *sixelScreen) showSixels() {
+	if sxs.sixel == nil {
+		return
+	}
+
+	// XXX: workaround for bug where quitting lf might leave the terminal in bold
+	fmt.Print("\033[0m")
+
+	fmt.Print("\0337")                              // Save cursor position
+	fmt.Printf("\033[%d;%dH", sxs.yprev, sxs.xprev) // Move cursor to position
+	fmt.Print(*sxs.sixel)                           //
+	fmt.Print("\0338")                              // Restore cursor position
+}
+
+func (sxs *sixelScreen) printSixel(win *win, screen tcell.Screen, reg *reg) {
+	if reg.sixel == nil {
+		return
+	}
+
+	// HACK: fillers are used to control when tcell redraws the region where a sixel image is drawn.
+	// alternating between bold and regular is to clear the image before drawing a new one.
+	st := sxs.fillerStyle(reg.path)
+	for y := 0; y < win.h; y++ {
+		st = win.print(screen, 0, y, st, strings.Repeat(string(gSixelFiller), win.w))
+	}
+
+	sxs.xprev, sxs.yprev = win.x+1, win.y+1
+	sxs.sixel = reg.sixel
+}

ui.go

@@ -252,7 +252,7 @@ func (win *win) printRight(screen tcell.Screen, y int, st tcell.Style, s string)
 	win.print(screen, win.w-printLength(s), y, st, s)
 }
 
-func (win *win) printReg(screen tcell.Screen, reg *reg, previewLoading bool) {
+func (win *win) printReg(screen tcell.Screen, reg *reg, previewLoading bool, sxs *sixelScreen) {
 	if reg == nil {
 		return
 	}
@@ -274,6 +274,8 @@ func (win *win) printReg(screen tcell.Screen, reg *reg, previewLoading bool) {
 
 		st = win.print(screen, 2, i, st, l)
 	}
+
+	sxs.printSixel(win, screen, reg)
 }
 
 var gThisYear = time.Now().Year()
@@ -558,6 +560,7 @@ func getWins(screen tcell.Screen) []*win {
 
 type ui struct {
 	screen      tcell.Screen
+	sxScreen    sixelScreen
 	polling     bool
 	wins        []*win
 	promptWin   *win
@@ -600,6 +603,7 @@ func newUI(screen tcell.Screen) *ui {
 		styles:      parseStyles(),
 		icons:       parseIcons(),
 		currentFile: "",
+		sxScreen:    sixelScreen{},
 	}
 
 	go ui.pollEvents()
@@ -679,6 +683,7 @@ type reg struct {
 	loadTime time.Time
 	path     string
 	lines    []string
+	sixel    *string
 }
 
 func (ui *ui) loadFile(app *app, volatile bool) {
@@ -955,6 +960,7 @@ func (ui *ui) draw(nav *nav) {
 			ui.screen.SetContent(i, j, ' ', nil, st)
 		}
 	}
+	ui.sxScreen.sixel = nil
 
 	ui.drawPromptLine(nav)
 
@@ -1003,7 +1009,7 @@ func (ui *ui) draw(nav *nav) {
 					&dirStyle{colors: ui.styles, icons: ui.icons, role: Preview},
 					nav.previewLoading)
 			} else if curr.Mode().IsRegular() {
-				preview.printReg(ui.screen, ui.regPrev, nav.previewLoading)
+				preview.printReg(ui.screen, ui.regPrev, nav.previewLoading, &ui.sxScreen)
 			}
 		}
 	}
@@ -1033,6 +1039,11 @@ func (ui *ui) draw(nav *nav) {
 	}
 
 	ui.screen.Show()
+	if ui.menuBuf == nil && ui.cmdPrefix == "" && ui.sxScreen.sixel != nil {
+		ui.sxScreen.lastFile = ui.regPrev.path
+		ui.sxScreen.showSixels()
+	}
+
 }
 
 func findBinds(keys map[string]expr, prefix string) (binds map[string]expr, ok bool) {