Tag / C#

by jake

Glide update: Tween overwriting

I’ve just added support for property overwriting to Glide, my Tweening engine for C#. This functionality exists in Actuate (a great Haxe library from which I’ve taken a lot of inspiration) and I’ve wanted it in Glide for a while now because it’s just so darn handy.

Imagine you start a tween off on its way:

// move image to (100, 200) over five seconds
Tweener.Tween(image, new { X = 100, Y = 200 }, 5);

…but then something changes, and now you want your image to travel instead to (X = 500) instead, and it should only take two seconds:

Tweener.Tween(image, new {X = 500}, 2);

At first this will work fine, but when the second tween finishes, suddenly the first one takes precedence again and your image will keep moving towards (X = 100). You could cancel the first tween, but that would also cancel the movement towards (Y = 200).

Now, creating a new Tween on an object that’s already being tweened will cancel the movement of any properties that are currently being tracked. In the example above, the new X tween would overwrite the old one, the original Y tween would keep on working, and there’s no need to manually cancel anything.

The old behavior is still available; just pass false to the overwrite parameter. I’m pretty sure that won’t be necessary in the majority of cases, but it does exist if you want it.

by jake

Glide update: Structs don’t work that way

Glide has seen some modest adoption despite the fact that I’ve barely made any effort to get the word out. A handful of developers have contacted me thanking me for the project and asking for help, which I’m always glad to offer. One issue in particular has come up a few times recently, and it relates to the way .NET handles structs.

Structs are passed and returned by value, not reference. This means that when you assign an instance to a variable, that new variable has no relationship to the original object; any properties set on it will only apply to that variable. This is a problem in Glide, since I have to store a reference to the tween’s target object in order to apply the transformations. Worst of all, while normally this issue would be caught at compile time, it’s impossible to detect when you’re using reflection to set values, and the resulting behavior was that the operation would appear to silently fail.

Today I made some changes that should help users realize when they’re attempting to tween an incompatible type. Passing an instance of a struct to the tweener will result in a compile-time error, and if you sneakily box your variable into an Object it will throw an exception at runtime. This still doesn’t solve the problem of how to tween these types of properties, but I’ve got you covered on that front as well.

Glide already has support for extension classes that allow you to add specialized behavior for tweening your own types, but this feature wasn’t really documented anywhere. Now it is! I’ve added a wiki to the Glide Bitbucket repository with an example showing how to tween an XNA Vector2. It should be pretty simple to modify for your own needs…maybe a StringTyper extension that causes letters to show up over time like a typewriter, or a GlitchString that fills the whole string with garbage and slowly fills in the correct letters.

by jake

Glide update: From()

I made a small addition to Glide, my tweening library for C#. You can now specify starting positions for the variables you’re tweening, useful for when you need to change a variable instantly and then tween back to the default value. I use this when I’m making things flash for alerts or other important things for the player to notice.

tweener.Tween(sprite, new { Scale = 1 }, 1)
    .From(new { Scale = 1.5f });

Obviously you could just set the values manually before telling them to tween, but this is a nice shortcut if you’re setting a lot of them at once.

You can download Glide here.