ae-mixin-developer

name: ae-mixin-developer description: Add methods to existing mixins or create new mixins for the After Effects automation client

AE Mixin Developer

This skill covers adding methods to the mixin-based Client architecture and creating new mixins. The Client class in ae_automation/__init__.py composes six mixins via multiple inheritance.

Mixin Composition

The Client is assembled in ae_automation/__init__.py:

class Client(
    afterEffectMixin,       # ae_automation/mixins/afterEffect.py
    ToolsMixin,             # ae_automation/mixins/tools.py
    botMixin,               # ae_automation/mixins/bot.py
    VideoEditorAppMixin,    # ae_automation/mixins/VideoEditorApp.py
    TemplateGeneratorMixin, # ae_automation/mixins/templateGenerator.py
    ProcessManagerMixin,    # ae_automation/mixins/processManager.py
):
    JS_FRAMEWORK = ""

    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        # Loads settings, creates cache folder, reads json2.js + framework.js
        # Replaces {CACHE_FOLDER} in framework.js with actual path (forward slashes)

Methods from any mixin are accessible as self.methodName() on the Client instance. All mixins share self state.

The runScript() Pattern

The core bridge between Python and AE. Located in afterEffect.py:

def runScript(self, fileName, _remplacements=None, debug=False):

Replacement Dict Rules

Keys must include braces. Values must be strings (it's string replacement, not formatting):

self.runScript("my_script.jsx", {
    "{comp_name}": str(comp_name),
    "{layer_name}": str(layer_name),
    "{startTime}": str(start_time),
    "{duration}": str(duration),
    "{value}": str(value),
})

Common mistake: Forgetting braces in keys.

# WRONG -- placeholder won't be found
{"comp_name": str(comp_name)}

# CORRECT
{"{comp_name}": str(comp_name)}

What runScript() Does

1. Reads the JSX file from settings.JS_DIR
2. Applies all replacements from the dict
3. Prepends minified JS_FRAMEWORK (json2.js + framework.js)
4. Wraps in try { ... } catch(e) { ... } outputLogs(_error);
5. Writes composed script to settings.CACHE_FOLDER
6. Sends to AE via the file-based queue system
7. Returns a UUID string (useful for reading log output)

Text Sanitization

Always call self.sanitize_text_for_ae() on any user-facing text before passing it to JSX. This method:

• Converts HTML <br> tags (all variants) to AE carriage returns (\r)
• Preserves straight quotes to avoid UTF-8 encoding issues

def myMethod(self, comp_name, layer_name, text):
    sanitized = self.sanitize_text_for_ae(text)
    self.runScript("my_script.jsx", {
        "{comp_name}": str(comp_name),
        "{layer_name}": str(layer_name),
        "{value}": str(sanitized),
    })

When to call it: Any time the value comes from user input or config and might contain HTML or special characters. The existing editComp() and editLayerAtKey() methods call it automatically.

Path Handling

JavaScript/ExtendScript requires forward slashes in file paths. When constructing paths for JSX:

# Convert backslashes to forward slashes for JS
js_path = path.replace("\\", "/")

self.runScript("import_file.jsx", {
    "{filePath}": js_path,
})

The settings module handles this for CACHE_FOLDER already (see __init__.py constructor), but any new paths you construct must be converted manually.

Color Handling

self.hexToRGBA() converts hex color strings to AE's normalized RGBA format:

color = self.hexToRGBA("#FF0000")
# Returns: "1.0,0.0,0.0,1"

The returned string is comma-separated with values in 0.0-1.0 range, with alpha always 1. This is the format AE expects for color properties.

In parseCustomActions(), this conversion happens automatically when property_type == "color":

if "property_type" in custom_edit:
    if custom_edit["property_type"] == "color":
        custom_edit["value"] = self.hexToRGBA(custom_edit["value"])

Method Naming Conventions

The codebase uses mixed conventions. Follow the convention of the mixin you're modifying:

When creating a new mixin, prefer snake_case (the modern convention used in ProcessManagerMixin).

Wait Patterns

After calling runScript(), you need to wait for AE to execute the script. The wait time depends on operation complexity:

# Simple property change
self.runScript("update_properties.jsx", replacements)
time.sleep(1)

# File import or composition creation
self.runScript("add_resource.jsx", replacements)
time.sleep(2)

# Complex operation (duplication, rendering setup)
self.runScript("duplicate_comp_2.jsx", replacements)
time.sleep(3)

# Very complex (full project creation)
self.runScript("create_new_project.jsx", replacements)
time.sleep(5)

The base runScript() already has a time.sleep(1) at the end. Additional sleeps in your method are on top of that.

For more reliable waiting, use the ProcessManagerMixin pattern:

self.safe_script_execution("my_script.jsx", replacements, wait_time=3)

Reading Data Back from AE

JSX scripts can write data files that Python reads:

JSX side (in your .jsx file):

var result = { items: [] };
// ... populate result ...
saveFile("my_output.json", JSON.stringify(result));

Python side (in your mixin method):

import json
from ae_automation import settings

def getMyData(self, comp_name):
    self.runScript("my_data_script.jsx", {
        "{comp_name}": str(comp_name),
    })
    time.sleep(2)  # wait for AE to write the file

    output_path = os.path.join(settings.CACHE_FOLDER, "my_output.json")
    with open(output_path, "r", encoding="utf-8") as f:
        return json.load(f)

Creating a New Mixin

1. Create the mixin file

ae_automation/mixins/my_feature.py:

"""
My Feature Mixin
Provides functionality for [description]
"""
import os
import time
from ae_automation import settings


class MyFeatureMixin:
    """Mixin that adds [feature] capabilities to the Client."""

    def do_something(self, comp_name, value):
        """
        Description of what this method does.

        Args:
            comp_name: Name of the target composition
            value: The value to set
        """
        sanitized_value = self.sanitize_text_for_ae(value)

        self.runScript("my_script.jsx", {
            "{comp_name}": str(comp_name),
            "{value}": str(sanitized_value),
        })
        time.sleep(2)

    def get_data(self):
        """Retrieve data from AE."""
        self.runScript("get_data.jsx")
        time.sleep(2)

        output_path = os.path.join(settings.CACHE_FOLDER, "data_output.json")
        import json
        with open(output_path, "r", encoding="utf-8") as f:
            return json.load(f)

2. Register the mixin in __init__.py

Add the import and include it in the Client class:

from ae_automation.mixins.my_feature import MyFeatureMixin

class Client(
    afterEffectMixin,
    ToolsMixin,
    botMixin,
    VideoEditorAppMixin,
    TemplateGeneratorMixin,
    ProcessManagerMixin,
    MyFeatureMixin,          # Add here
):

3. Create corresponding JSX scripts

Place them in ae_automation/mixins/js/ following the patterns in the jsx-script-creator skill.

Settings Module Constants

Available via from ae_automation import settings:

Adding a New change_type

To add a new action type to the config system:

1. Add the handler in parseCustomActions()

In ae_automation/mixins/afterEffect.py, add a new if block:

def parseCustomActions(self, custom_edit, scene_folder, itemTimeline, data):
    # ... existing handlers ...

    if custom_edit["change_type"] == "my_new_action":
        self.myNewAction(
            self.slug(scene_folder) + "_" + custom_edit["comp_name"],
            custom_edit["other_field"],
        )

Note the self.slug() prefix pattern: Scene-specific compositions are named {scene_slug}_{template_comp}. The slug() method (from ToolsMixin) creates a URL-safe version of the scene folder name.

2. Implement the method

def myNewAction(self, comp_name, other_field):
    self.runScript("my_new_action.jsx", {
        "{comp_name}": str(comp_name),
        "{other_field}": str(other_field),
    })
    time.sleep(2)

3. Create the JSX script

ae_automation/mixins/js/my_new_action.jsx -- see the jsx-script-creator skill.

4. Document in config schema

Add the new change_type to the config-schema reference.

Complete Example: Adding a Layer Visibility Toggle

JSX script (ae_automation/mixins/js/toggle_layer_visibility.jsx):

//
// Toggle Layer Visibility
// ------------------------------------------------------------
// Language: javascript
//

function toggleLayerVisibility(compName, layerName, visible) {
    var comp = FindItemByName(compName);
    if (!comp) {
        print("Composition not found: " + compName);
        return;
    }
    var layer = FindLayerByComp(compName, layerName);
    if (!layer) {
        print("Layer not found: " + layerName);
        return;
    }
    layer.enabled = visible;
    print("Set " + layerName + " visibility to " + visible);
}

toggleLayerVisibility("{comp_name}", "{layer_name}", {visible});

Python method (in afterEffect.py or a new mixin):

def toggleLayerVisibility(self, comp_name, layer_name, visible):
    self.runScript("toggle_layer_visibility.jsx", {
        "{comp_name}": str(comp_name),
        "{layer_name}": str(layer_name),
        "{visible}": "true" if visible else "false",
    })
    time.sleep(1)

Config integration (in parseCustomActions()):

if custom_edit["change_type"] == "toggle_visibility":
    self.toggleLayerVisibility(
        self.slug(scene_folder) + "_" + custom_edit["comp_name"],
        custom_edit["layer_name"],
        custom_edit.get("visible", True),
    )

Config usage:

{
  "change_type": "toggle_visibility",
  "comp_name": "IntroTemplate",
  "layer_name": "Watermark",
  "visible": false
}