Editor scripts

You can create custom menu items and editor lifecycle hooks using Lua files with special extension: .editor_script. Using this system, you can tweak editor to enhance your development workflow.

Editor script runtime

Editor scripts run inside an editor, in a Lua VM emulated by Java VM. All scripts share the same single environment, which means they can interact with each other. You can require Lua modules, just as with .script files, but Lua version that is running inside the editor is different, so make sure your shared code is compatible. Editor uses Lua version 5.2.x, more specifically luaj runtime, which is currently the only viable solution to run Lua on JVM. Besides that, there are some restrictions:

  • there is no debug and coroutine packages;
  • there is no os.execute — we provide a more user-friendly and secure way to execute shell scripts in actions section;
  • there is no os.tmpname and io.tmpfile — currently editor scripts can access files only inside the project directory;
  • there is currently no os.rename, although we want to add it;
  • there is no os.exit and os.setlocale.

All editor extensions defined in editor scripts are loaded when you open a project. When you fetch libraries, extensions are reloaded, since there might be new editor scripts in a libraries you depend on. During this reload, no changes in your own editor scripts are picked up, since you might be in the middle of changing them. To reload them as well, you should run Project → Reload Editor Scripts command.

Anatomy of .editor_script

Every editor script should return a module, like that:

local M = {}

function M.get_commands()
  -- TODO
end

return M

Editor then collects all editor scripts defined in project and libraries, loads them into single Lua VM and calls into them when needed (more on that in commands and lifecycle hooks sections).

Editor API

You can interact with the editor using editor package that defines this API:

  • editor.platform — a string, either "x86_64-win32" for Windows, "x86_64-darwin" for macOS or "x86_64-linux" for Linux.
  • editor.get(node_id, property) — get a value of some node inside the editor. Nodes in the editor are various entities, such as script or collection files, game objects inside collections, json files loaded as resources, etc. node_id is a userdata that is passed to the editor script by the editor. Alternatively, you can pass resource path instead of node id, for example "/main/game.script". property is a string. Currently these properties are supported:
    • "path" — file path from the project folder for resources — entities that exist as files. Example of returned value: "/main/game.script"
    • "text" — text content of a resource editable as text (such as script files or json). Example of returned value: "function init(self)\nend". Please note that this is not the same as reading file with io.open(), because you can edit a file without saving it, and these edits are available only when accessing "text" property.
    • some properties that are shown in the Properties view when you have selected something in the Outline view. These types of outline properties supported:
      • strings
      • booleans
      • numbers
      • vec2/vec3/vec4
      • resources

      Please note that some of these properties might be read-only, and some might be unavailable in different contexts, so you should use editor.can_get before reading them and editor.can_set before making editor set them. Hover over property name in Properties view to see a tooltip with information about how this property is named in editor scripts. You can set resource properties to nil by supplying "" value.

  • editor.can_get(node_id, property) — check if you can get this property so editor.get() won’t throw an error
  • editor.can_set(node_id, property) — check if "set" action with this property won’t throw an error

Commands

If editor script module defines function get_commands, it will be called on extension reload, and returned commands will be available for use inside the editor in menu bar or in context menus in Assets and Outline panes. Example:

local M = {}

function M.get_commands()
  return {
    {
      label = "Remove Comments",
      locations = {"Edit", "Assets"},
      query = {
        selection = {type = "resource", cardinality = "one"}
      },
      active = function(opts)
        local path = editor.get(opts.selection, "path")
        return ends_with(path, ".lua") or ends_with(path, ".script")
      end,
      run = function(opts)
        local text = editor.get(opts.selection, "text")
        return {
          {
            action = "set",
            node_id = opts.selection,
            property = "text",
            value = strip_comments(text)
          }
        }
      end
    },
    {
      label = "Minify JSON"
      locations = {"Assets"},
      query = {
        selection = {type = "resource", cardinality = "one"}
      },
      active = function(opts)
        return ends_with(editor.get(opts.selection, "path"), ".json")
      end,
      run = function(opts)
        local path = editor.get(opts.selection, "path")
        return {
          {
            action = "shell",
            command = {"./scripts/minify-json.sh", path:sub(2)}
          }
        }
      end
    }
  }
end

return M

Editor expects get_commands() to return an array of tables, each describing a separate command. Command description consists of:

  • label (required) — text on a menu item that will be displayed to the user
  • locations (required) — an array of either "Edit", "View", "Assets" or "Outline", describes a place where this command should be available. "Edit" and "View" mean menu bar at the top, "Assets" means context menu in Assets pane, and "Outline" means context menu in Outline pane.
  • query — a way for command to ask editor for relevant information and define what data it operates on. For every key in query table there will be corresponding key in opts table that active and run callbacks receive as argument. Supported keys:
    • selection means this command is valid when there is something selected, and it operates on this selection.
      • type is a type of selected nodes command is interested in, currently these types are allowed:
        • "resource" — in Assets and Outline, resource is selected item that has a corresponding file. In menu bar (Edit or View), resource is a currently open file;
        • "outline" — something that can be shown in the Outline. In Outline it’s a selected item, in menu bar it’s a currently open file;
      • cardinality defines how many selected items there should be. If "one", selection passed to command callback will be a single node id. If "many", selection passed to command callback will be an array of one or more node ids.
  • active - a callback that is executed to check that command is active, expected to return boolean. If locations include "Assets" or "Outline", active will be called when showing context menu. If locations include "Edit" or "View", active will be called on every user interaction, such as typing on keyboard or clicking with mouse, so be sure that active is relatively fast.
  • run - a callback that is executed when user selects menu item, expected to return an array of actions.

Actions

Action is a table describing what editor should do. Every action has an action key. Actions come in 2 flavors: undoable and non-undoable.

Undoable actions

Undoable action can be undone after it is executed. If a command returns multiple undoable actions, they are performed together, and get undone together. You should use undoable actions if you can. Their downside is that they are more limited.

Existing undoable actions:

  • "set" — set a property of a node in the editor to some value. Example:
    {
      action = "set",
      node_id = opts.selection,
      property = "text",
      value = "current time is " .. os.date()
    }
    

    "set" action requires these keys:

    • node_id — node id userdata. Alternatively, you can use resource path here instead of node id you received from the editor, for example "/main/game.script";
    • property — a property of a node to set, currently only "text" is supported;
    • value — new value for a property. For "text" property it should be a string.

Non-undoable actions

Non-undoable action clears undo history, so if you want to undo such action, you will have to use other means, such as version control.

Existing non-undoable actions:

  • "shell" — execute a shell script. Example:
    {
      action = "shell",
      command = {
        "./scripts/minify-json.sh",
        editor.get(opts.selection, "path"):sub(2) -- trim leading "/"
      }
    }
    

    "shell" action requires command key, which is an array of command and it’s arguments. Main difference with os.execute is that since this is a potentially dangerous operation, editor will show a confirmation dialog asking user if they want to execute this command. It will remember each command that user already allowed.

Mixing actions and side effects

You can mix undoable and non-undoable actions. Actions are executed sequentially, hence depending on an order of actions you will end up losing ability to undo parts of that command.

Instead of returning actions from functions that expect them, you can just read and write to files directly using io.open(). This will trigger a resource reload that will clear undo history.

Lifecycle hooks

There is a specially treated editor script file: hooks.editor_script, located in a root of your project, in the same directory as game.project. This and only this editor script will receive lifecycle events from the editor. Example of such file:

local M = {}

function M.on_build_started(opts)
  local file = io.open("assets/build.json", "w")
  file:write("{\"build_time\": \"".. os.date() .."\"}")
  file:close()
end

return M

We decided to limit lifecycle hooks to single editor script file because order in which build hooks happen is more important than how easy it is to add another build step. Commands are independent from each other, so it does not really matter in what order they are shown in the menu, in the end user executes a particular command they selected. If it was possible to specify build hooks in different editor scripts, it would create a problem: in which order do hooks execute? You probably want to create a checksums of content after you compress it… And having a single file that establishes order of build steps by calling each step function explicitly is a way to solve this problem.

Every lifecycle hook can return actions or write to files in project directory.

Existing lifecycle hooks that /hooks.editor_script may specify:

  • on_build_started(opts) — executed when game is Built to run locally or on some remote target. Your changes, be it returned actions or updated file contents, will appear in a built game. Raising an error from this hook will abort a build. opts is a table that contains following keys:
    • platform — a string in %arch%-%os% format describing what platform it’s built for, currently always the same value as in editor.platform.
  • on_build_finished(opts) — executed when build is finished, be at successful or failed. opts is a table with following keys:
    • platform — same as in on_build_started
    • success — whether build is successful, either true or false
  • on_bundle_started(opts) — executed when you create a bundle or Build HTML5 version of a game. As with on_build_started, changes triggered by this hook will appear in a bundle, and errors will abort a bundle. opts will have these keys:
    • output_directory — a file path pointing to a directory with bundle output, for example "/path/to/project/build/default/__htmlLaunchDir"
    • platform — platform the game is bundled for. See a list of possible platform values in Bob manual.
    • variant — bundle variant, either "debug", "release" or "headless"
  • on_bundle_finished(opts) — executed when bundle is finished, be it successful or not. opts is a table with the same data as opts in on_bundle_started, plus success key indicating whether build is successful.
  • on_target_launched(opts) — executed when user launched a game and it successfully started. opts contains an url key pointing to a launched engine service, for example, "http://127.0.0.1:35405"
  • on_target_terminated(opts) — executed when launched game is closed, has same opts as on_target_launched

Please note that lifecycle hooks currently are an editor-only feature, and they are not executed by Bob when bundling from command line.

Editor scripts in libraries

You can publish libraries for other people to use that contain commands, and they will be automatically picked up by editor. Hooks, on the other hand, can’t be picked up automatically, since they have to be defined in a file that is in a root folder of a project, but libraries expose only subfolders. This is intended to give more control over build process: you still can create lifecycle hooks as simple functions in .lua files, so users of your library can require and use them in their /hooks.editor_script.

Also note that although dependencies are shown in Assets view, they do not exist as files (they are entries in a zip archive), so there is currently no easy way to execute a shell script you provide in a dependency. If you absolutely need it, you’ll have to extract provided scripts by getting their text using editor.get() and then writing them somewhere with file:write(), for example in a build/editor-scripts/your-extension-name folder.