+** Having tabs above a window to switch buffers in it.
+
+** "Perspectives" are named persistent window configurations. We have
+had the window configuration mechanism in GNU Emacs since the
+beginning but we have never developed a good user interface to take
+advantage of them. Eclipse's user interface seems to be good.
+
+Perspectives work well even if you do the equivalent of C-x 4 C-f
+because of the distinction between view windows vs file windows. In
+Emacs this is more or less the "dedicated window" feature, but we have
+never really made it work for this.
+
+Perspectives also need to interact with the tabs.
+
+** Imenu could be extended into a file-structure browsing mechanism
+using code like that of customize-groups.
+
+** Display something in the margin on lines that have compilation
+errors.
+
+** Compilation error navigation bar, parallel to the scroll bar,
+indicating where in the buffer there are compilation errors.
+Perhaps we could arrange to display these error indications on top
+of the scroll bar itself. That depends on to what extent toolkit
+scroll bars are extensible.
+