Media files cannot be selected or drag-and-dropped

[JakobKallin]

At present, image and sound files can only be used in adventures by specifying their URL or file path. This is due to several factors:

• <input type="file"> is notoriously difficult to style, making it inflexible to build a user interface around.
• Selected and drag-and-dropped files can only be referenced by their file data, not their URL or file path. This makes caching difficult, and it vastly increases the size of saved adventure files. The Filesystem API, which can solve these issues, is not widely supported.
• Basing the user interface on file selection or drag-and-drop makes it more difficult to allow URLs, especially since there is not a native HTML control that allows for selecting both files and URLs.
• Creating adventure files that link to files using relative paths becomes impossible if only the file data is read. This makes it impossible to store a standalone adventure on a USB stick, unless all the media data can be stored in the adventure file.

[JakobKallin]

This could also be solved using IndexedDB, which is supported in Chrome, Firefox, and (reportedly) IE10. Since the URLs are only valid for the current session, there is no risk of old files lying around. If support for manually defining paths and URLs is dropped, this could make file selection and drag-and-drop possible in current browsers.

[JakobKallin]

On second thought, the fact that IndexedDB URLs are not persisted over sessions means that auto-saving adventures is not possible, unlike a solution with local file paths or filesystem:// URLs.

[JakobKallin]

It turns out that the data inside the IndexedDB is actually persisted over sessions; it's the object URLs that are cleared when the window closes. This means that auto-saving adventures is indeed possible using IndexedDB.