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.

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.