How to bake dynamic paint surfaces headlessly?

Question

I have had a look at Baking smoke on a headless machine, however, I cannot figure out my way from there to bake dynamic paint on a headless machine. This is what I have come up with by now:

import bpy

for scene in bpy.data.scenes:
    for object in scene.objects:
        for modifier in object.modifiers:
            if modifier.type == 'DYNAMIC_PAINT':
                override = {'scene': scene, 'object': object}
                bpy.ops.dpaint.bake(override)
                break

However, I get:

PyContext 'window' not found
PyContext 'window' not found
PyContext 'window' not found
Error: Bake failed: invalid canvas
Error: Bake failed: invalid canvas

Traceback (most recent call last):
  File "/home/horazont/baker.py", line 8, in <module>
    bpy.ops.dpaint.bake(override)
  File "/usr/share/blender/2.69/scripts/modules/bpy/ops.py", line 186, in __call__
    ret = op_call(self.idname_py(), C_dict, kw, C_exec, C_undo)
RuntimeError: Error: Bake failed: invalid canvas


Blender quit

Which parameters do I have to pass to the operator?

Answer 1

import bpy

obj=bpy.data.objects['Cube']
modifier=obj.modifiers['Dynamic Paint']
canvas_surface=modifier.canvas_settings.canvas_surfaces['Surface']
point_cache=canvas_surface.point_cache

context={}
context['blend_data']=bpy.data
context['scene']=bpy.data.scenes['Scene']
context['active_object']=obj
context['point_cache']=point_cache

bpy.ops.ptcache.bake(context,bake=True)

Objects can be both a brush and a canvas. The baking is done by the surfaces of the canvas. So an additional iteration is necessary.

#...
for modifier in obj.modifiers:
    if modifier.type=='DYNAMIC_PAINT':
        #additional iteration
        for canvas_surface in modifier.canvas_settings.canvas_surfaces:
             context['active_object']=obj
             context['point_cache']=canvas_surface.point_cache
             bpy.ops.ptcache.bake(context,bake=True)