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
N - 1).
create_buttons(Grid, Frame,
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(!)
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?