yi-core-0.19.2: Yi editor core library
Safe HaskellSafe-Inferred




data UI e Source #

Record presenting a frontend's interface.

The functions layout and refresh are both run by the editor's main loop, in response to user actions and so on. Their relation is a little subtle, and is discussed here:

  • to see some code, look at the function refreshEditor in Yi.Core. This is the only place where layout and refresh are used.
  • the function layout is responsible for updating the Editor with the width and height of the windows. Some frontends, such as Pango, need to modify their internal state to do this, and will consequently change their display. This is expected.
  • the function refresh should cause the UI to update its display with the information given in the Editor.
  • the functionalities of layout and refresh overlap to some extent, in the sense that both may cause the frontend to update its display. The Yi core provides the following guarantees which the frontend may take advantage of:

    • in the main editor loop (i.e. in the refreshEditor function), layout will be run (possibly multiple times) and then refresh will be run. This guarantee will hold even in the case of threading (the function refreshEditor will always be run atomically, using MVars).
    • between the last run of layout and the run of refresh, some changes may be made to the Editor. However, the text, text attributes, and (displayed) window region of all windows will remain the same. However, the cursor location may change.

    This guarantee allows frontends which calculate rendering of the text during the layout stage to avoid recalculating the render again during refresh. Pango is an example of such a frontend.

The Yi core provides no guarantee about the OS thread from which the functions layout and refresh are called from. In particular, subprocesses (e.g. compilation, ghci) will run layout and refresh from new OS threads (see startSubprocessWatchers in Yi.Core). The frontend must be preparaed for this: for instance, Gtk-based frontends should wrap GUI updates in postGUIAsync.