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Source code editor in pure Go.
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Source code editor in pure Go.






  • This is a know-what-you're-doing 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 (uses guru and/or gopls query if installed).
    • 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).

Installation and usage

go get -u
cd $GOPATH/src/
go build 
# windows 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)
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,extensions,network{tcp,tcpclient,stdio},cmd,optional{stderr}
    	go,.go,tcp,"gopls serve -listen={{.Addr}}"
    	go,.go,stdio,"gopls serve"
    	c++,".c .h .cpp .hpp",stdio,clangd
  -plugins string
    	comma separated string of plugin filenames
    	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)
  -wraplinerune int
    	code for wrap line rune, can be set to zero (default 8592)

Since the editor has no configuration file, it is suggested you use it within a script with your preferences (example

exec ~/code/jmigpin/editor/editor \
--dpi=143 \
--fontsize=9 \
--colortheme=acme \
--commentscolor=0x008b00 \
--stringscolor=0x8b3100 \
--lsproto=go,.go,tcp,"gopls serve -listen={{.Addr}}" \
--lsproto=c++,".c .h .cpp .hpp",stdio,clangd,stderr \

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 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 $edPosOffset -to abc Usage of external command with active row position as argument. gorename godoc, go tools.
  • guru -scope fmt callers $edPosOffset 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).


Top 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

Row toolbar commands

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

  • 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: 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.
  • XdgOpenDir: calls xdg-open to open the row directory with the preferred external application (ex: 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.
  • GoRename <new-name>: calls gorename to rename 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.
  • GoDebug <command> [arguments]: debugger utility for go programs (more at commands:godebug)

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

	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)
	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=:8080 main.go
	GoDebug connect -addr=:8080
  • Annotate files

    • By default, the current directory will be annotated. Other files/directories can be added with the -dirs and -files command line options, but it is also possible to annotate by inserting one of the following comments in the code (notice the lack of space):
      The annotator will detect these comments and annotate the block/file/package/module. 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:
       func fn(){
       	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
  • Limitations:

    • String methods are not annotated to avoid endless loops (the annotation would recursively call the String method again).
    • 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()) // myfunc1 returns 2 arguments (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.
  • Notes:

    • The annotated executable pauses if a client is not connected. In other words, it stops sending debug messages until a client connects.
    • use esc key to stop the debug session. Check related shortcuts at the key/buttons shortcuts section.
    • Supports remote debugging (check help usage).
      • 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

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>: 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: when set on a row toolbar, filters terminal escape sequences. Currently only the clear escape sequence esc[J is interpreted to clear the textarea. Other escape sequences are removed from the output.

Environment variables set available to external commands

  • $edName: row name.
  • $edDir: row directory.
  • $edPosOffset: filename with offset position from active row cursor. Ex: "filename:#123".
  • $edLine: line from active row cursor. Ex: "12".

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
  • 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+f: warp pointer to "Find" cmd in row toolbar
  • buttonLeft on square-button: close row
  • on top border:
    • 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
  • 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 + text area cmd
    • 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+down: move line down
    • ctrl+alt+shift+down: duplicate lines
    • ctrl+d: comment lines
    • ctrl+shift+d: uncomment lines
  • godebug
    • ctrl+buttonLeft: select annotation
    • ctrl+buttonRight: over an annotation: print the annotation value.
    • ctrl+buttonWheelUp:
      • on textarea: show previous debug step
      • over an annotation: show line previous annotation
    • ctrl+buttonWheelDown:
      • on textarea: show next debug step
      • over an annotation: show line next annotation
    • ctrl+f5:
      • on textarea: show last debug step
    • ctrl+f9:
      • on textarea: clear debug messages (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, a mod-key+tab can be pressed (ex: ctrl, alt, ...).

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


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