Izzatbek Mukhanov edited this page Jul 22, 2016 · 8 revisions

Libpointing

An open-source cross-platform library to get raw events from pointing devices and master transfer functions.

Overview

Libpointing is an open-source cross-platform library that provides direct access to HID pointing devices and supports the design of pointing transfer functions.

The library

  • runs on Windows, Mac OS X and Linux,
  • makes it easy to choose the devices at run-time through the use of URIs,
  • provides raw information from input devices,
  • provides resolution and frequency information for the available pointing and display devices,
  • supports hot-plugging
  • allows to bypass the system's transfer functions to receive raw asynchronous events from one or more pointing devices.
  • replicates as faithfully as possible the transfer functions used by Microsoft Windows, Apple OS X and Xorg (the X.Org Foundation server).
  • running on these three platforms, it makes it possible to compare the replicated functions to the genuine ones as well as custom ones.
  • provides the functionality to use existing transfer functions, custom ones or even build your own functions.
  • supports subpixel interaction.
  • Java, Python, Node.js bindings are available.

Minimalistic example

Once you correctly installed libpointing and linked it to your project, simply write #include <pointing/pointing.h> and start coding. Here is the console example which applies system specific transfer function to an input device and outputs the results to console:

#include <iostream>
#include <pointing/pointing.h>

using namespace pointing;

TransferFunction *func = 0;

// context is user data, timestamp is a moment at which the event was received
// input_dx, input_dy are displacements in horizontal and vertical directions
// buttons is a variable indicating which buttons of the pointing device were pressed.
void pointingCallback(void *, TimeStamp::inttime timestamp, int input_dx, int input_dy, int buttons)
{
    if (!func) return;

    int output_dx = 0, output_dy = 0;
    // In order to use a particular transfer function, its applyi method must be called.
    func->applyi(input_dx, input_dy, &output_dx, &output_dy, timestamp);

    std::cout << "Displacements in x and y: " << input_dx << " " << input_dy << std::endl;
    std::cout << "Corresponding pixel displacements: " << output_dx << " " << output_dy << std::endl;
}

int main()
{
    // Basically, to start using main functionality of libpointing
    // one needs to create objects of PointingDevice, DisplayDevice classes,
    // connect them passing to TransferFunction class object.

    // Any available pointing and display devices
    // if debugLevel > 0, the list of available devices
    // and extended information will be output.
    PointingDevice *input = PointingDevice::create("any:?debugLevel=1");
    DisplayDevice *output = DisplayDevice::create("any:?debugLevel=1");

    func = TransferFunction::create("sigmoid:?debugLevel=2", input, output);

    // To receive events from PointingDevice object, a callback function must be set.
    input->setPointingCallback(pointingCallback);
    while (1)
        PointingDevice::idle(100); // milliseconds

    delete input;
    delete output;
    delete func;

    return 0;
}

A more extended example can be found here.

That is it, in this manner you can apply any available transfer function on the chosen input. Enjoy!

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