Accessing files dropped onto the application window

Cinder applications can respond to files dropped onto the application window through the callback, fileDrop . This method takes a ci::app::FileDropEvent object as a parameter with information about the event.

Getting ready

Your application must implement a fileDrop method which takes a ci::app::FileDropEvent object as a parameter.

Add the following method to the application's class declaration:

void fileDrop( FileDropEvent event );

How to do it…

We will learn how to work with the ci::app::FileDropEvent object to work with file drop events. Perform the following steps to do so:

1. In the method implementation you can use the ci::app::FileDropEvent parameter to access the list of files dropped onto the application by calling the getFiles method. This method returns a conststd::vector container with fs::path objects:

   const vector<fs::path >& files = event.getFiles();

2. The position where the files were dropped onto the window can be accessed through the following callback methods:

   • To get a ci::Vec2i object with the position of the files dropped, type in the following line of code:

     Vec2i dropPosition = event.getPos();

   • To get the x and y coordinates separately, you can use the getX and getY methods, for example:

     int pOS X = event.getX();
     int posY = event.getY();

3. You can find the number of dropped files by using the getNumFiles method:

   int numFiles = event.getNumFiles();

4. To access a specific file, if you already know its index, you can use the getFile method and pass the index as a parameter.

   For example, to access the file with an index of 2, you can use the following line of code:

   const fs::path& file = event.getFile( 2 );

How it works…

A Cinder application will respond to the system's native event for file drops. It will then create a ci::app::FileDropEvent object with information about the event and call the fileDrop callback in our application. This way Cinder creates a uniform way of responding to file drop events across the Windows and OS X platforms.

There's more…

Cinder uses ci::fs::path objects to define paths. These are typedef instances of boost::filesystem::path objects and allow for much greater flexibility when working with paths. To learn more about the fs::path objects, please refer to the boost::filesystem library reference, available at http://www.boost.org/doc/libs/1_50_0/libs/filesystem/doc/index.htm.