Freon Documentation (version 0.5.0)

Writing Actions in TypeScript

When you have created your own custom projection, this projection is exactly that: a projection. Other than the built-in default behavior (held in the file ~/picode/editor/<yourLanguageName>DefaultActions.ts), there are no actions defined yet. Actions are necessary to enable the user to change the model and add elements to it. The projections only describe what you will see in the editor. Actions determine what you can do, how you interact with the editor.

As a convenience, the file ~/picode/editor/Custom<yourLanguageName>Actions.ts is generated, which is a placeholder for your own actions written in TypeScript. This file contains four constants for different kind of actions. What you need to do is to define these constants. Then Freon will merge your actions with the default actions. If a trigger for an action is identical to a default one, your custom actions take precedence.

export const MANUAL_EXPRESSION_CREATORS: PiExpressionCreator[] = [
    // Add your own custom expression creators here

export const MANUAL_BINARY_EXPRESSION_CREATORS: PiBinaryExpressionCreator[] = [
    // Add your own custom binary expression creators here

export const MANUAL_CUSTOM_BEHAVIORS: PiCustomBehavior[] = [
    // Add your own custom behavior here

export const MANUAL_KEYBOARD: KeyboardShortcutBehavior[] = [
    // Add your own custom keyboard shortcuts here

Creation of New Elements

Now, let’s start with adding an element, e.g. adding a new property to an Entity.

From Actions you will have learned that an AliasBox is a predefined box where the user can type text to trigger some action. Thus, we add an AliasBox to the projection of the property list. Note the role of the box: end-of-property-list.

// tutorial-language/editor/CustomEntityProjection.ts#L141-L146

new VerticalListBox(entity,"attributes", => {
        return this.getBox(att);
).addChild(new AliasBox(entity, "end-of-attribute-list",
    "add attribute"))

Then we create the actual action and attach it to the role of the AliasBox. Note that the projection and action are defined in two different files, respectively CustomEntityProjections.ts and CustomEntityActions.ts.

// tutorial-language/editor/CustomEntityActions.ts#L40-L51

        activeInBoxRoles: ["end-of-attribute-list"],                                            // <1>
        trigger: "attribute",                                                                   // <2>
        action: (box: Box, trigger: PiTriggerType, editor: PiEditor): PiElement | null => {     // <3>
            var entity: Entity = box.element as Entity;
            const attribute: AttributeWithLimitedType = new AttributeWithLimitedType();
            return attribute;
        boxRoleToSelect: "Attribute-name"                                                       // <4>

The numbers in the comments indicate what happens here:

  1. The action is attached to each box with the role “end-of-property-list”.
  2. The action will be triggered when the user types "attribute" inside the AliasBox.
  3. The executable code for the action. It creates a new AttributeWithLimitedType and attaches is to entity
  4. The focus of the editor is returned to the Box with the role "Attribute-name" within the entity. This ensures that the user can immediately start typing the name of the entity after it has been created.

There can be many boxes with the same role in the editor, as long as their model element is different. This way, the above action is available for each attribute list in each entity.

Custom Actions

// TODO document other custom actions

Expressions and Binary Expressions

// TODO Advanced expression editing.

Keyboard Shortcuts

// TODO A keyboard shortcut specifies an action that is triggered by special keys, like e.g. Ctrl-A.