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Source code editor in pure Go.






  • This is a simple but advanced source code editor
  • As the editor is being developed, the rules of how the UI interacts will become more well defined.
  • Primarily developed and tested in Linux.
  • Works in MS Windows (native or xserver) and MacOS (xserver).


  • Auto-indentation of wrapped lines.
  • No code coloring (except comments and strings).
  • Many TextArea utilities: undo/redo, replace, comment, ...
  • Handles big files.
  • Start external processes from the toolbar with a click, capturing the output to a row.
  • Drag and drop files/directories to the editor.
  • Detects if files opened are changed outside the editor.
  • Plugin support
    • examples such as gotodefinition and autocomplete below.
  • Golang specific:
    • Calls goimports if available when saving a .go file.
    • Clicking on .go files identifiers will jump to the identifier definition (needs gopls).
    • Debug utility for go programs (GoDebug cmd).
      • allows to go back and forth in time to consult code values.
  • Language Server Protocol (LSP) (code analysis):
    • -lsproto cmd line option
    • basic support for gotodefinition and completion
    • mostly being tested with clangd and gopls
  • Inline complete
    • code completion by hitting the tab key (uses LSP).


Instalation with git

Get with git the latest from the default master branch:

git clone

Build and run:

cd ./editor
go build

Windows platform compilation alternatives:

go build				# shows one console window (will be hidden, but makes a flash)
go build -ldflags -H=windowsgui		# hides the console window, but cmds will popup consoles
go build -tags=xproto 			# (not native, needs an x11 server to run)

Instalation with go tooling to be used as a library

go get -u

Please take care to distinguish between versions and ensure "go get" is actually getting the version you want.

To use a specific commit inside a go.mod, use the commit hash. For example: for the v3.0.0 the hash starts with a08876d10e639487f5. So inside the go.mod goes:

require a08876d10e63

The command go mod tidy will replace that line with:

require v1.y.z-0.20201021185104-a08876d10e63

Note that because the go compiler insists that a project must follow the vX directories, on projects that stopped doing it, it will now show v1.y.z, even though it will be using the inserted commit hash of v3.0.0.


Usage of ./editor:
  -colortheme string
    	available: light, dark, acme (default "light")
  -commentscolor int
    	Colorize comments. Can be set to zero to use a percentage of the font color. Ex: 0=auto, 1=Black, 0xff0000=red.
  -cpuprofile string
    	profile cpu filename
  -dpi float
    	monitor dots per inch (default 72)
  -font string
    	font: regular, medium, mono, or a filename (default "regular")
  -fonthinting string
    	font hinting: none, vertical, full (default "full")
  -fontsize float
    	 (default 12)
  -lsproto value
    	Language-server-protocol register options. Can be specified multiple times.
    	Format: language,fileExtensions,network{tcp,tcpclient,stdio},cmd,optional{stderr}
    		go,.go,stdio,"gopls serve"
    		go,.go,tcp,"gopls serve -listen={{.Addr}}"
    		cpp,".c .h .cpp .hpp .cc",stdio,clangd
  -plugins string
    	comma separated string of plugin filenames
  -presavehook value
    	Run program before saving a file. Uses stdin/stdout. Can be specified multiple times. By default, a "goimports" entry is auto added if no entry is defined for the "go" language.
    	Format: language,fileExtensions,cmd
    		cpp,".c .h .cpp .hpp",clang-format
    	set scrollbars on the left side (default true)
  -scrollbarwidth int
    	Textarea scrollbar width in pixels. A value of 0 takes 3/4 of the font size.
  -sessionname string
    	open existing session
    	shadow effects on some elements (default true)
  -sn string
    	open existing session
  -stringscolor int
    	Colorize strings. Can be set to zero to not colorize. Ex: 0xff0000=red.
  -tabwidth int
    	 (default 8)
    	use multi-key to compose characters (Ex: [multi-key, ~, a] = ã)
    	output version and exit
  -wraplinerune int
    	code for wrap line rune, can be set to zero (default 8592)

The editor has no configuration file. Use it within a script with your preferences (example

exec ~/path/editor \
--dpi=143 \
--fontsize=9 \
--colortheme=acme \
--commentscolor=0x008b00 \
--stringscolor=0x8b3100 \
--lsproto=go,.go,stdio,"gopls serve" \
--lsproto="cpp,\".c .h .cpp .hpp .cc\",stdio,clangd" \
--presavehook=go,.go,goimports \
--presavehook="cpp,\".c .h .cpp .hpp\",\"clang-format --someoption\"" \

Basic Layout

The editor has a top toolbar and columns. Columns have rows. Rows have a toolbar and a textarea.

These row toolbars are also textareas where clicking (buttonRight) on the text will run that text as a command.

The row toolbar has a square showing the state of the row.

Toolbar usage examples

Commands in toolbars are separated by "|" (not to be confused with the shell pipe). If a shell pipe is needed it should be escaped with a backslash.

All internal commands start with an Uppercase letter. Otherwise it tries to run an existent external program.


  • ~/tmp/subdir/file1.txt | ls Clicking at ls will run ls at ~/tmp/subdir
  • ~/tmp/subdir/file1.txt | ls -l \| grep fi Notice how "|" is escaped, allowing to run ls -l | grep fi
  • ~/tmp/subdir/file1.txt Clicking at file1.txt opens a new row to edit the same file. Clicking at ~/tmp opens a new row located at that directory.
  • gorename -offset $edFileOffset -to abc Usage of external command with active row position as argument. gorename godoc, go tools.
  • guru -scope fmt callers $edFileOffset Usage of external command with active row position as argument. guru godoc, go tools.
  • grep -niIR someword Grep results with line positions that are clickable.
  • xdg-open $edDir Open favorite external application with active row directory.
  • xterm Open an xterm at the active row directory.
  • $font=mono Use monospaced font in this row textarea (see more at internal variables).


Toolbar commands

  • ListSessions: lists saved sessions
  • SaveSession <name>: save session to ~/.editor_sessions.json
  • DeleteSession <name>: deletes the session from the sessions file
  • NewColumn: opens new column
  • NewRow: opens new empty row located at the active-row directory, or if there is none, the current directory. Useful to run commands in a directory.
  • ReopenRow: reopen a previously closed row
  • SaveAllFiles: saves all files
  • ReloadAll: reloads all filepaths
  • ReloadAllFiles: reloads all filepaths that are files
  • ColorTheme: cycles through available color themes.
  • FontTheme: cycles through available font themes.
  • Exit: exits the program
  • Version: shows editor version in the messages row

Row toolbar commands

These commands run on a row toolbar, or on the top toolbar with the active-row.

  • NewFile <name>: create (and open) new file at the row directory. Fails it the file already exists.
  • Save: save file
  • Reload: reload content
  • CloseRow: close row
  • CloseColumn: closes row column
  • Find: find string (ignores case)
  • GotoLine <num>: goes to line number
  • Replace <old> <new>: replaces old string with new, respects selections
  • Stop: stops current process (external cmd) running in the row
  • ListDir [-sub] [-hidden]: lists directory
    • -sub: lists directory and sub directories
    • -hidden: lists directory including hidden
  • MaximizeRow: maximize row. Will push other rows up/down.
  • CopyFilePosition: output the cursor file position in the format "file:line:col". Useful to get a clickable text with the file position.
  • RuneCodes: output rune codes of the current row text selection.
  • FontRunes: output the current font runes.
  • OpenFilemanager: open the row directory with the preferred external application (usually a filemanager).
  • LsprotoCloseAll: closes all running lsp client/server connections. Next call will auto start again. Useful to stop a misbehaving server that is not responding.
  • LsprotoRename <new-name>: Renames the identifiers under the text cursor using the loaded lsp instance. Uses the row/active-row filename, and the cursor index as the "offset" argument.
  • GoRename [-all] <new-name>: Renames the identifier under the text cursor. Uses the row/active-row filename, and the cursor index as the "offset" argument. Reloads the calling row at the end if there are no errors.
    • default: calls gopls (limited scope in renaming, but faster).
    • -all: calls gorename to rename across packages (slower).
  • GoDebug <command> [arguments]: debugger utility for go programs (more at commands:godebug)
  • GoDebugFind <string>: find string in current selected annotation. Useful to rewind the annotations to the desired point.

Row name at the toolbar (usually the filename)

  • Clicking on a section of the path of the filename will open a new row with that content. Ex: if a row filename is "/a/b/c.txt" clicking on "/a" will open a new row with that directory listing, while clicking on "/a/b/c.txt" will open another row to edit the same file.

Textarea commands

  • OpenSession <name>: opens previously saved session
  • <url>: opens url in preferred application.
  • <filename(:number?)(:number?)>: opens filename, possibly at line/column (usual output from compilers). Check common locations like $GOROOT and C include directories.
    • If text is selected, only the selection will be considered as the filename to open.
  • <identifier-in-a-.go-file>: opens definition of the identifier. Ex: clicking in Println on fmt.Println will open the file at the line that contains the Println function definition.

Commands: GoDebug

Output of GoDebug -help:

	GoDebug <command> [arguments]
The commands are:
	run		build and run program with godebug data
	test		test packages compiled with godebug data
	build 	build binary with godebug data (allows remote debug)
	connect	connect to a binary built with godebug data (allows remote debug)
Env variables:
	GODEBUG_BUILD_FLAGS	comma separated flags for build
	GoDebug -help
	GoDebug run -help
	GoDebug run main.go -arg1 -arg2
	GoDebug run -dirs=dir1,dir2 -files=f1.go,f2.go main.go -arg1 -arg2
	GoDebug test -help
	GoDebug test
	GoDebug test -run mytest
	GoDebug build -addr=:8008 main.go
	GoDebug connect -addr=:8008
	GoDebug run -env=GODEBUG_BUILD_FLAGS=-tags=xproto main.go

Output of GoDebug run -help:

Usage of GoDebug run:
  -dirs string
    	comma-separated string of directories to annotate
  -env string
    	string with env variables (ex: "GOOS=os:..."'
  -files string
    	comma-separated string of files to annotate
    	Don't send msgs in chunks (slow). Useful to get msgs before a crash.
  -toolexec string
    	execute cmd, useful to run a tool with the output file (ex: wine outputfilename)
    	verbose godebug
    	print workdir and don't cleanup on exit
  • Annotate files
    • By default, the main file will be annotated. Other files/directories can be added with the -dirs and -files command line options, or by inserting one of the following comments in the code (notice the lack of space after "//"):

       //godebug:annotateimport 	# use before an "import" line
       # or specify a target
       //godebug:annotatefile:<file> 	# absolute or relative to the current
       //godebug:annotatemodule:<pkg-path> 	# any pkg path inside will annotate all

      The annotator will detect these comments and annotate accordingly.

      A pkg path can be given to annotatepackage, but beware that pkgs located in $GOROOT are not annotated. Example:


      Higher level //godebug:* comments will override lower ones. To disable annotating for the current code block, insert:


      This is helpful to bypass loops that would become too slow with debug messages being sent. Example:

       //godebug:annotateoff	// don't annotate arg "v1"
       func fn(v1 int){
       	//godebug:annotateblock		// re-enable annotations
       	a:=0 // annotated
       	if a==0{
       		a++ // annotated
       		a+=2 // *not* annotated
       		a+=3 // *not* annotated
       		for i:=0; i<10000;i++{
       			// *not* annotated
       	println(a) // annotated, not part of the disabled block

      Also, to improve on the String() limitation:

       type myint int
       func (v myint) String() string {
       	return f1(v)
       // would cause endless loop with godebug calling t.String() at arg `v`
       // but not if it the annotations are off
       func fn(v myint) string { 
       	return fmt.Sprintf("%d", v) 
  • Limitations:
    • String() and Error() methods are not annotated to avoid endless loops (the annotation would recursively call the method again).
    • fixed Go supports multi-value function assignment. These statements are annotated but give a compilation error later:
       - func myfunc1() (int,int) { return 1, 2}
       - func myfunc2(a int, b int) {}
       - ...
       - myfunc2(myfunc1()) // assumes myfunc1 returns 1 arg (compilation err)
      The annotator assumes myfunc1 returns 1 value. For this to be solved the annotator would have to become substantially slower with type analysis.
    • fixed Constants bigger then int get the int type when assigned to an interface{} Consider the following code that compiles and runs:
       - a:=uint64(0)
       - a=math.MaxUint64
      But, the following gives a compile error:
       - var a interface{}
       - a=math.MaxUint64
       - // compilation err: constant 18446744073709551615 overflows int
      When the code is annotated, there are debug functions that have interface{} arguments. So if an argument is a const bigger then int, it won't work. A solution is to use //godebug:annotateoff before the offending line. For this to be solved, the types need to be analysed but that would become substantially slower (compiles are not cached).
  • Notes:
    • Use esc key to stop the debug session. Check related shortcuts at the key/buttons shortcuts section.
    • Supports remote debugging (check help usage with GoDebug -h).
      • The annotated executable pauses if a client is not connected. In other words, it stops sending debug messages until a client connects.
      • A client can connect/disconnect any number of times, but there can be only one client at a time.
    • Example usage of setting the env var in a godebug session:
       GoDebug run -env=GO111MODULE=off main.go
      The example below builds a binary for windows in another platform, for later remote debug:
       GoDebug build -env=GOOS=windows -addr=:8008 main.go
       ... (copy the binary to the target platform and run it) ...
       GoDebug connect -addr=:8008

Internal variables

  • ~<digit>=path: Replaces long row filenames with the variable. Ex.: a file named /a/b/c/d/e.txt with ~0=/a/b/c defined in the top toolbar will be shortened to ~0/d/e.txt.
  • $font=<name>[,<size>]: sets the row textarea font when set on the row toolbar. Useful when using a proportional font in the editor but a monospaced font is desired for a particular program output running in a row. Ex.: $font=mono.
  • $termFilter: same as $terminal=f
  • $terminal={f,k}: enable terminal features.
    • f: Filter (remove) escape sequences from the output. Currently only the clear display sequence is interpreted in this mode which clears the output (usefull for running programs that want to discard old ouput).
    • k: redirect keyboard input to the running program to enable reading from standard input. Note: typing keys will not be seen in the textarea unless the running program outputs them (exceptions: "\n") .

Environment variables set available to external commands

  • $edName: row name.
  • $edDir: row directory.
  • $edFileOffset: filename with offset position from active row cursor. Ex: "filename:#123".
  • $edFileLine: index line from active row cursor (1-based). Ex: "12".
  • $edFileWord: word at index from active row cursor. Ex: "myvar". Usage ex: use go doc $edFileWord with cursor at a receiver variable.
  • $<name>=<string>: set custom variable in a row toolbar to be set in the environment when running an external command.
    Example row toolbar:
     $myprog="a.out -arg1"
     $myprog -arg2 | echo a${myprog}b
    Clicking on $myprog -arg2 will have the shell run a.out -arg1 -arg2.
    Clicking on echo a${myprog}b will result in echoing aa.out -arg1b.

Row states

  • background colors:
    • blue: row file has been edited.
    • orange: row file doesn't exist.
  • dot colors:
    • black: row currently active. There is only one active row.
    • red: row file was edited outside (changed on disk) and doesn't match last known save. Use Reload cmd to update.
    • blue: there are other rows with the same filename (2 or more).
    • yellow: there are other rows with the same filename (2 or more). Color will change when the pointer is over one of the rows.


Plugins allow extra functionality to be added to the editor without changing the binary.

A plugin can be compiled and run with (will output a *.so):

go build -buildmode=plugin plugin1.go
go build -buildmode=plugin plugin2.go
editor --plugins,

Functions that can be implemented by a plugin are (subject to changes - work-in-progress ):

func OnLoad(ed *core.Editor)
func AutoComplete(ctx context.Context, ed *core.Editor, cfb *ui.ContextFloatBox) (err error, handled bool) // error` is only considered if `handled` is true
func ToolbarCmd(ed *core.Editor, erow *core.ERow, part *toolbarparser.Part) bool

Note that plugins might need to be recompiled everytime there are changes in the libraries provided by the editor.

Editor events currently implemented (subject to changes - work-in-progress ):

PostNewERowEEventId // on erow creation
PostFileSaveEEventId // after a file is saved
PreRowCloseEEventId // before a row is closed
RowStateChangeEEventId // on row state change (duplicate rows also emit).

Plugins located at: ./plugins.

  • gotodefinition_godef.go: plugin that shows how to override the textarea click action and use godef instead of the default.
  • autocomplete_gocode.go: plugin that shows a context with suggestions for .go files (uses gocode).
  • rownames.go: example plugin that shows how to access row names.
  • eevents.go: example plugin on how to access editor events.

Key/button shortcuts

Global key/button shortcuts

  • esc:
    • stop debugging session
    • close context float box
    • cancels any cmds running (content,internal,preSaveHooks,...)
  • f1: toggle context float box
    • triggers call to plugins that implement AutoComplete
    • esc: close context float box

Column key/button shortcuts

  • buttonLeft:
    • on left border: drag to move/resize
    • on square-button: close

Row key/button shortcuts

  • ctrl+s: save file
  • ctrl+w: close row
  • ctrl+f: warp pointer to "Find" cmd in row toolbar
  • ctrl+h: warp pointer to "Replace" cmd in row toolbar
  • ctrl+n: warp pointer to "NewFile" cmd in row toolbar
  • buttonLeft on square-button: close row
  • on top border (or row square):
    • buttonLeft: drag to move/resize row
    • buttonMiddle: close row
    • buttonWheelUp: adjust row vertical position, pushing other rows up
    • buttonWheelDown: adjust row vertical position, pushing other rows down
  • Any button/key press: make row active to layout toolbar commands

Textarea key/button shortcuts

  • basic keyboard navigation
    • left: move cursor left
    • right: move cursor right
    • up: move cursor up
    • down: move cursor down
    • home: start of line
    • end: end of line
    • delete: delete current rune
    • backspace: delete previous rune
    • pageUp: page up
    • pageDown: page down
    • ctrl+left: jump to previous word start
    • ctrl+right: jump to next word end
  • basic mouse navigation
    • buttonLeft: move cursor to point
      • drag: selects text - works as copy making it available for paste (primary selection).
      • double-click: selects word
      • triple-click: selects line
    • shift+buttonLeft: move cursor to point adding to selection
    • buttonRight: move cursor to point + run textarea command
    • buttonWheelUp: scroll up
    • buttonWheelDown: scroll down
    • buttonWheelUp on scrollbar: page up
    • buttonWheelDown on scrollbar: page down
  • selection
    • shift+left: move cursor left adding to selection
    • shift+right: move cursor right adding to selection
    • shift+up: move cursor up adding to selection
    • shift+down: move cursor down adding to selection
    • shift+home: start of string adding to selection
    • shift+end: end of string adding to selection
    • ctrl+a: select all
  • copy/paste
    • ctrl+c: copy to clipboard
    • ctrl+v: paste from clipboard
    • ctrl+x: cut
    • buttonMiddle: paste from primary
  • undo/redo
    • ctrl+z: undo
    • ctrl+shift+z: redo
  • utils
    • tab (if selection is on): insert tab at beginning of lines
    • shift+tab: remove tab from beginning of lines
    • ctrl+k: remove lines
    • ctrl+alt+up: move line(s) up
    • ctrl+alt+down: move line(s) down
    • ctrl+alt+shift+down: duplicate lines
    • ctrl+d: comment lines
    • ctrl+shift+d: uncomment lines
  • godebug
    • ctrl+buttonLeft: select debug step
    • ctrl+buttonRight: over a debug step: print the value.
    • ctrl+buttonRight+shift: over a debug step: print all previous values up to the debug step.
    • ctrl+buttonWheelUp:
      • show previous debug step
      • over a debug step: show line previous debug step
    • ctrl+buttonWheelDown:
      • show next debug step
      • over a debug step: show line next debug step
    • ctrl+f4: show first debug step
    • ctrl+f5: show last debug step
    • ctrl+f9: clear all debug steps (clears memory, continues debugging)
    • esc: stop the debug session.
  • inline complete
    • tab: inline code completion for file extensions registered with LSP.
      • if the previous rune is not a space, it runs code completion. To force tab insertion, press modkey+tab (ex: ctrl, alt, ...).
    • esc: stop inline completion.
    • Changing the cursor position also stops inline completion.

Row placement algorithm

When a new row is created, it is placed either below the current row (measuring available space), or in a "good position".

The "good position" measures the available space between all rows, and uses the position with the most space.

The measuring of space is done as follows:

  1. if the cursor is visible, measure space after visible cursor to the end of the textarea and use it if not smaller than two lines in height, otherwise use 2)
  2. about 2/3 of the textarea



  • 2021/07/27: v3.1.0 (40 commits)
    • Support for go 1.16 default modules mode
    • Version cmd line option
    • Many godebug fixes.
    • Other minor fixes.
  • 2020/10/21: v3.0.0 (11 commits)
    • Changed directory structure (no vX dir for version).
    • Reduce dependencies.
    • Fix lsproto tests.
    • Other minor fixes.
  • 2020/05/06: v2.0.7 (23 commits)
    • fixes towards making the project go-getable with v2.
  • 2020/05/05: v2.0.1 (3 commits)
    • terminal output bug fix (overwrites).
  • 2020/05/01: v2.0.0 (92 commits)
    • Internal API changes/improvements
    • Improvements on godebug stability and added features
    • Improvements on lsproto stability
    • Performance improvements
    • Many bug fixes.
  • 2020/02/22: v1.1.1 (9 commits)
    • lsproto: critial bug fix (#36).
    • windows: critical bug fix (#37).
    • other small bug fixes
  • 2020/02/19: v1.1.0 (133 commits)
    • godebug: adds "//godebug:*" comment directives. Go modules support improved.
    • inline tab complete
    • windows: support case-insensitive filesystem
    • windows: drag and drop improvements.
    • many bug fixes and overall improvements on stability.
  • 2019/12/28: v1.0.0 (1049 commits)
    • first tagged release
    • drawer improvements (handle big files)
    • fs watcher for changed files
    • language server protocol (go to definition, completion, ...)
    • plugins
    • unix: drag and drop
  • 2016/10/11:
    • development start


Source code editor in pure Go.








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