wxErlang Mats-Ola Persson

wxErlang GUI library for Erlang write GUI applications cross platform cross platform look and feel

Example A “stupid” tic-tac-toe application No intelligent behavior is implemented Just the (good) looks

Creating a window create_window() -> wx:start(), % initialize wxErlang % create a frame (window) with no parent Frame = wx:frame(?NULL, ?wxID_ANY, “Hello World!”), wx:show(Frame). % make the frame visible

Creating a window Not very exciting: an empty window

Event-driven programming Things “react” to mouse clicks, mouse movements, etc. Event-handlers, callback functions

Events create_window() -> wx:start(), Frame = wx:frame(?NULL, ?wxID_ANY, “Hello World!”), % event-handler that reacts to close clicks wx:connect(Frame, ?wxEVT_CLOSE_WINDOW, fun(_,_) -> wx:quit() end), wx:show(Frame).

Layouts Platform independent layouts Sizers No fixed sized widgets, etc. Arbitrary complex layouts Let’s add the buttons!

Sizers create_grid(Frame) -> Grid = wx:grid_sizer(3), % a grid sizer with 3 cols create_buttons(Grid, Frame, 9), % create 9 buttons Grid. create_buttons(_, _, 0) -> ok;create_buttons(Grid, Frame, N) -> Button = wx:button(Frame, N), %a button without label wx:add(Grid, Button), % add button to the sizer create_buttons(Grid, Frame, N - 1).

The result A “shell” of a tic-tac-toe application

wxEtop Port of the old “etop” New features context menues view running code ...

From the programmers point of view wxErlang is verbose - like most GUI libraries Trial-and-error - like most GUI libraries Interface designers XRCed, DialogBlocks, etc.

Design decisions Binding to the C++ GUI library wxWidgets Get a lot for free “free” features from wxWidgets reduced maintenance work wxErlang interface resembles wxWidgets C++ interface free documentation(!) Varför wxWidgets?

Translation scheme Easy Functions Multiple return values => tuples ... Constants

Translation scheme Not as easy Classes Overloading and overriding functions Type system

Safety Checks arguments Types Primitive values Objects Sanity

Implementational details Most of the code is generated from wxWidgets headers Implemented as a “port program” Has a lot of bugs

Wrap up Current status - a prototyp wxEtop Perhaps 10% implemented Future

Questions?