PluginExample.cpp

This example demonstrates how widgets can be made into plugins.

Screenshot of our minimalistic PluginExample

Plugins are widgets that can be instantiated by a string. They can be loaded dynamically during runtime instead of having to be statically linked in.

In this example, we create a simple custom widget that modulates its background color as a function of time:

  class SampleWidget : public MultiWidgets::Widget
  {
  public:
    SampleWidget() : m_age(0) {}

    // Implement simple color modulation
    virtual void update(const MultiWidgets::FrameInfo & frameInfo) OVERRIDE
    {
      MultiWidgets::Widget::update(frameInfo);
      // Color modulation:
      m_age += frameInfo.dt();
      setBackgroundColor(std::sin(m_age * 1.31f) * 0.5f + 0.5f,
                         std::sin(m_age * 1.53f) * 0.5f + 0.5f,
                         std::cos(m_age * 1.87f) * 0.5f + 0.5f,
                         1.0f);
    }

  private:
    // Age in seconds for color modulation
    float m_age;
  };

To create a plugin from the widget, we just need to use a simple macro:

  WIDGET_PLUGIN(SampleWidget, "Cornerstone.Examples.PluginExample", "PluginExample")

This macro creates the data structures necessary to load the plugin. Basically, it creates a factory function that creates an instance of the SampleWidget when called. This factory function is automatically registered to the MultiWidgets::Plugins class. It can be instantiated with MultiWidgets::createPlugin function.

Full source code for the example is listed below:

/* Copyright (C) 2007-2013 Multi Touch Oy, Finland, http://www.multitaction.com
 *
 * This file is part of MultiTouch Cornerstone.
 *
 * All rights reserved. You may use this file only for purposes for which you
 * have a specific, written permission from Multi Touch Oy.
 *
 */

#include <MultiWidgets/Application.hpp>
#include <MultiWidgets/Plugins.hpp>

namespace Examples
{

  class SampleWidget : public MultiWidgets::Widget
  {
  public:
    SampleWidget() : m_age(0) {}

    // Implement simple color modulation
    virtual void update(const MultiWidgets::FrameInfo & frameInfo) OVERRIDE
    {
      MultiWidgets::Widget::update(frameInfo);
      // Color modulation:
      m_age += frameInfo.dt();
      setBackgroundColor(std::sin(m_age * 1.31f) * 0.5f + 0.5f,
                         std::sin(m_age * 1.53f) * 0.5f + 0.5f,
                         std::cos(m_age * 1.87f) * 0.5f + 0.5f,
                         1.0f);
    }

  private:
    // Age in seconds for color modulation
    float m_age;
  };

  WIDGET_PLUGIN(SampleWidget, "Cornerstone.Examples.PluginExample", "PluginExample")

}

int main(int argc, char** argv)
{
  MultiWidgets::Application app;

  if(!app.init(argc, argv))
    return 1;

  auto w = MultiWidgets::createPlugin("Cornerstone.Examples.PluginExample");

  app.mainLayer()->addChild(w);
  w->setSize(app.mainLayer()->size());

  return app.run();
}