Add-on: use the 'eval' description in the 'eval now' button as well

In the tooltip of the 'evaluate now' button (the one with the Python
icon), include the description provided by the job type in its
`evalInfo.description` field. This makes it explicit what the button
will do when pressed.

addon/flamenco/gui.py

@@ -126,6 +126,7 @@ class FLAMENCO_PT_job_submission(bpy.types.Panel):
         props = layout.operator("flamenco.eval_setting", text="", icon="SCRIPTPLUGINS")
         props.setting_key = setting.key
         props.setting_eval = setting_eval
+        props.eval_description = job_types.eval_description(setting)
 
     def draw_setting_readonly(
         self,

addon/flamenco/job_types.py

@@ -91,6 +91,17 @@ def show_eval_on_submit_button(setting: _AvailableJobSetting) -> bool:
     return show_button
 
 
+def eval_description(setting: _AvailableJobSetting) -> str:
+    """Return the 'eval description' of this setting, or an empty string if not found."""
+
+    eval_info = setting.get("eval_info", None)
+    if not eval_info:
+        return ""
+
+    description: str = eval_info.get("description", "")
+    return description
+
+
 def setting_autoeval_propname(setting: _AvailableJobSetting) -> str:
     """Return the property name of the 'auto-eval' state for this setting."""
     return f"autoeval_{setting.key}"

addon/flamenco/operators.py

@@ -143,6 +143,14 @@ class FLAMENCO_OT_eval_setting(FlamencoOpMixin, bpy.types.Operator):
     setting_key: bpy.props.StringProperty(name="Setting Key")  # type: ignore
     setting_eval: bpy.props.StringProperty(name="Python Expression")  # type: ignore
 
+    eval_description: bpy.props.StringProperty(name="Description", options={"HIDDEN"})
+
+    @classmethod
+    def description(cls, context, properties):
+        if not properties.eval_description:
+            return ""  # Causes bl_description to be shown.
+        return f"Set value to: {properties.eval_description}"
+
     def execute(self, context: bpy.types.Context) -> set[str]:
         job = job_submission.job_for_scene(context.scene)
         if job is None: