This is what a user sees when starting the debugger the first time and the Tracer is enabled. We should either increase the default width (might be a bad idea imho because font sizes are inconsistent between platforms, and you don't need that much width just for the sources, which is the default tab), or do something more smart. Another concern of mine is that a user will have to considerably increase the width of the sidebar for the traces to be in any way visually useful.

Comment on attachment 8347063 [details] Screen Shot 2013-12-13 at 09.06.04.png I say we remove the horizontal padding and let flex do its thing, s/Call Stack/Stack/, remove the "start tracing" button and only show the "tracing has not started" message and center it (bug 949908).

I'm not entirely sure about renaming "Call Stack" to just "Stack", since some people might wonder whether this displays "variables from the stack" or something. "So where's the heap?" The message should look like in the other widgets, "This page has no sources." or "No stack frames to display", to keep a consistent appearance and hot have things all over the place. Using the "emptyText" in WidgetMethods should work nicely, provided that FastListWidget handles the "notice" attribute appropriately. Everything else makes sense.

(In reply to Victor Porof [:vp] from comment #3) > I'm not entirely sure about renaming "Call Stack" to just "Stack", since > some people might wonder whether this displays "variables from the stack" or > something. "So where's the heap?" The JS spec doesn't distinguish between stack vs. heap storage AFAIK (it's just an engine optimization if and when it happens), so I don't think it's likely that developers would be confused. I don't believe I've ever seen any JS debugger present a variables-on-the-stack display, and I'm not sure whether it's feasible to even implement something like that without essentially undoing the optimization.