Add scripted_expression helper function

Author: carson-katri

api/node_mapper.py

@@ -30,6 +30,8 @@ def build(_primary_arg=None, **kwargs):
                     value = value.value
                 setattr(node, prop.identifier, value)
         for node_input in (node.inputs[1:] if _primary_arg is not None else node.inputs):
+            if not node_input.enabled:
+                continue
             argname = node_input.name.lower().replace(' ', '_')
             all_with_name = []
             for node_input2 in (node.inputs[1:] if _primary_arg is not None else node.inputs):

api/static/expression.py

@@ -0,0 +1,6 @@
+def scripted_expression(scripted_expression: str) -> 'Type':
+    from geometry_script import Type, State
+    value_node = State.current_node_tree.nodes.new('ShaderNodeValue')
+    fcurve = value_node.outputs[0].driver_add("default_value")
+    fcurve.driver.expression = scripted_expression
+    return Type(value_node.outputs[0])

api/tree.py

@@ -8,6 +8,7 @@
 from .types import *
 from .node_mapper import *
 from .static.input_group import *
+from .static.expression import *
 
 def _as_iterable(x):
     try:

api/types.py

@@ -38,6 +38,8 @@ def __init__(self, socket: bpy.types.NodeSocket = None, value = None):
                 tuple: ('FunctionNodeInputVector', 'vector'),
                 float: ('ShaderNodeValue', None),
             }
+            if type(value) == int:
+                print("Making an integer node?")
             if not type(value) in input_nodes:
                 raise Exception(f"'{value}' cannot be expressed as a node.")
             input_node_info = input_nodes[type(value)]

book/src/SUMMARY.md

@@ -21,6 +21,7 @@
     - [Input Groups](./api/advanced-scripting/input-groups.md)
     - [Attributes](./api/advanced-scripting/attributes.md)
     - [Boolean Math](./api/advanced-scripting/boolean-math.md)
+    - [Drivers](./api/advanced-scripting/drivers.md)
 
 # Tutorials
 

book/src/api/advanced-scripting/drivers.md

@@ -0,0 +1,10 @@
+# Drivers
+
+Drivers can be used with geometry nodes. To create a scripted expression driver, use the `scripted_expression` convenience function.
+
+This can be used to get information like the current frame number in a Geometry Script.
+
+```python
+frame_number = scripted_expression("frame")
+frame_number_doubled = scripted_expression("frame * 2")
+```