Every time we build an app platform, we get this feature request with approximately one use case: letting calendar apps show the current date in the calendar icon, rather than a generic icon with the wrong date.

While web apps can change their favicon dynamically (e.g., Google Calendar does this with its favicon), there is no way to programmatically change the manifest icon, which is used by platforms as the "shelf" or system icon.

I wonder if this is feasible. Potential problems are:

• Spoofing (an app could change its icon dynamically to look like another popular app, and the user would not be explicitly told that the app icon is changing).
• Use of the feature to create a "badge" (e.g., unread count). Potentially useful, but I think we want a separate badge feature so it can show a badge in a manner consistent with the host OS. (This is something we're separately discussing.)
• Fairly limited use case. Nothing really, other than a calendar app, has a use for this. (We had an open feature request on this for Chrome Apps platform for years and nobody suggested any other use case.)