Displaying keyframed opacity / transparency in Material mode in viewport? If I drag to change the Alpha value for a material, it updates continuously in the viewport when viewport_shade is set to Material; the object appears to fade in and out.

However, if I use keyframes to change that same value, the display does not update. What's going on? Is this a bug?

Notes:


I don't think this is a duplicate of this question because the asker seems to be referring to Rendered mode rather than Material mode. It's a little unclear what mode he was referring to, but there is no useful answer to my question there, and that question is 2 years old.
I have enabled Transparency under Display in the object properties.
I have set Shading to GLSL.
I'm using Blender 2.7.4 on Kubuntu 14.04 64 with a Nvidia GTX 750 Ti.
You can replicate this simply by creating a cube, giving it alpha transparency and doing as described above.
I am fairly certain this is a limitation of the current system. Simply put the changes in material settings don't trigger updates in the viewport. Manually altering values in the node editor or the material properties causes the UI to deliberately send an update event to the viewport, keyframed changes during playback don't. The keyframed changes do pass through to the render engine though.

I wouldn't expect this to change until the new dependency graph work is finished.