Python

Python bindings

Getting started

If you want to use libpointing with Python, you need to compile it yourself (look this page).

Main functionality

Once you compiled the bindings, you can import pylibpointing and start using it.

Or import main classes:

from pylibpointing import PointingDevice, DisplayDevice, TransferFunction
from pylibpointing import PointingDeviceManager, PointingDeviceDescriptor

Working with input

Creating a pointing device:

input = PointingDevice("any:?debugLevel=1") # Any input URI

Start receiving HID events from a device:

def cb_fct(timestamp, dx, dy, button):
    print(dx, dy, timestamp, button)

input.setCallback(cd_fct)

Hot-plugging callback for input devices:

def cb_man(desc, wasAdded):
    print desc
    print "was added" if wasAdded else "was removed"

pm = PointingDeviceManager()
pm.addDeviceUpdateCallback(cb_man)

Enumerating PointingDeviceDescriptors:

for desc in pm:
    print desc

You can access the following properties of a PointingDevice:

• uri
• vendorID
• productID
• vendor
• product
• resolution
• updatefrequency

Working with output

Creating a display device:

output = DisplayDevice("any:");

You can access the following properties of a DisplayDevice:

• uri
• size { width, height }
• bounds { size: { width, height }, origin: { x, y } }
• refreshrate
• resolution { hppi, vppi }

Working with transfer functions

TransferFunction class maps the input counts of a PointingDevice to the pixel coordinates of a DisplayDevice.

Creating a transfer function:

tfunc = TransferFunction("any:", input, output);

List of available methods:

• applyi(dx, dy, timestamp) // Integer output
• applyd(dx, dy, timestamp) // Float output
• clearState()
• setSubPixeling(value) // By default it is turned off
• setHumanResolution(resolution)
• setCardinalitySize(cardinality, size)

List of properties:

• uri
• subPixeling
• cardinality
• widgetSize
• humanResolution

Note that in Python version of libpointing all transfer functions support subpixeling and the uri property returns the original transfer function URI.

Applying a transfer function to the input:

def cb_fct(timestamp, dx, dy, button):
    rx,ry = tfunc.applyd(dx, dy, timestamp)
    print("%s: %d %d %d -> %.2f %.2f"%(str(timestamp), dx, dy, button, rx, ry ))

input.setCallback(cb_fct)