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User Notifications in Hieroglyph 3

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The final big ToDo in my list of Hieroglyph updates that were accumulated while writing our book was to add a better error handling system. There were many occasions where a shader would not compile properly, which basically caused a crash or a null pointer exception. In most cases, data is logged to the debug log and it is easy to figure out what happened, but in general it wasn't the way that it should be done. So I decided to take a look around and decide what to update or modify to give a more graceful exit strategy.

[subheading]Communication Issues[/subheading]

In Hieroglyph 3, there is already a rudimentary event system that can be used to simplify communication between various disparate classes in the engine. For error handling, I wanted to stick with this same mechanism - partially because it was already there and partially because I'm not the most familiar with writing exception based code. In addition, all of the sample applications have already been setup to receive and handle events, so it was really a no brainer to stick with the existing system.

So I created two new event classes, EvtInfoMessage and EvtErrorMessage. The former will simply notify the user of something, while the latter will both inform and then request an end to the application. After a few quick tests, the system was up and running without much more than half an hour, and could gracefully an application without dumping all over itself.


After deciding how the system will indicate that something unexpected has happened, it was time to decide how best to communicate this to the user (i.e. the developer debugging his code). I really have three choices in this regard. Hieroglyph 3 has fairly robust support for multiple windows, so I could simply pop up a new window and give the message. This could be done with raw win32 (as I have done for my Lua console window) or with the built in text rendering system that has been discussed previously. The former is kind of clunky, although almost surely would always be functional. The later depends on the engine itself, which may or may not be functioning properly in an error situation.

This led me to choose the third option - to use the good old windows MessagBox function. It will more or less always be functional, but is significantly easier to use than a raw win32 window. This also lets me use different icons for an error or an info message, and automatically handles the addition of buttons to the window too (I'm not using the buttons for anything now, but I could in the future...). This results in the following style messages for when a shader fails to load instead of an exception:


With the general system now being operational, it is just a matter of going through the engine and adding the creation and launching of one of the new events in each error situation. This may seem like a small step forward, but it already has sped up the development of an application. As always, the code is available to check out at the Hieroglyph 3 codeplex repository.

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