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FTW - Common Lisp For the Win(32)

1. Introduction

This library provides a very thin interface to the underlying APIs for writing native Windows GUIs in Common Lisp.

The intention is to be able to write the same sort of codes in Lisp as you would if writing normal Win32 GUIs in C. This also opens the possibility for writing other more general graphical applications like games.

2. Functions

All underlying Win32 functions have Lisp equivalents, mostly with CamelCase replaced with the Lisp style kebab-case.

Because this is a very thin wrapper over the top of the underlying Win32 API, it is assumed the user is at least familiar with the equivalent C programming. Documentation for each of the functions can be found on MSDN or any of the other C language resource.

2.1 Limitations

Several functions accept IDs for so called "resources", which normally get linked in with the object code by the resource compiler (when writing in C). For obviously reasons this is not possible when using Lisp.

2.2 Other platforms

This is a Windows only library and does not work on any other platform. It is not a cross platform GUI library.

3. Extra utilities

Several extra functions and macros are provided which the author has found useful. These are found in ftw.lisp.

3.1 Constants

To use the Win32 API you need access to a vast number of predefined constants. These are defined in constants.lisp. Rather than export each of these symbols from the FTW package the programmer has two options: either access directly or use the macros const or logior-consts:

;; directly 
(logior ftw::+fred+ ftw::+jim+)
;; sugar coating macro 
(ftw:const +fred+)
(ftw:logior-consts +fred+ +jim+)

The macro CONST takes a string designator and converts to the symbol with that name in the FTW package. In many places you need to pass a bitmask of logical-OR of several flags, use LOGIOR-CONSTS for this which performs the same transformation.

Note that there are possibly many constants which have not been defined in constants.lisp. These should be added over time as they become useful.

3.2 Resources

When writing Win32 programs in the C programming language it is common to embed binary resources such as icons, cursors and bitmaps using the resource compiler. These can then be referenced by an integer ID from various Win32 calls. This is not possible when calling these functions at from Lisp because we have to do everthing at runtime. Where possible I have included the functions for generating these at runtime either by loading from files or from raw binary data.

To make it easier I have also included several functions for pregenerating Lisp code for icons, cursors and bitmaps. This has the equivalent semantics as the normal Win32 resource compiler but we're still doing all the work at runtime.

The advantage of pregenerating code and putting that into your project is you don't need to ship external images which need to be loaded at runtime - you need only compile your code.

To e.g. embed an icon into your project do the following:

  1. Get your icon file e.g. by drawing it in gimp. make sure it is 32x32 pixels and exported as 32-bit with 8 bits each of alpha and rgb.
  2. Run (ftw:generate-icon-resource "myicon.ico") This will print out the code you need to paste into your project.

See the minesweeper example of how you can have a custom icon without shipping the file separately.

3.3 Dialogs

The standard mechanism for drawing modal and modeless dialogs with Win32 is to use the resource compiler to generate the specification. This is not possible for us so we must do it at runtime.

The functions DIALOG-BOX and CREATE-DIALOG create modal and modeless dialogs respectively. Both accept the same inputs. The difference is that modal dialogs do not return control to the caller until the dialog has been closed whereas modeless dialogs return control immediately and run alongside the original window.

3.4 Hwnd registry

You may associate a window handle (hwnd) with a symbol name and optionally integer ID using REGISTER-HWND. Perform lookups by name or ID using HWND-BY-NAME and HWND-BY-ID:

;; register an hwnd with the name FRED and ID 1
(register-hwnd 'fred hwnd 1) 
;; lookup hwnd with name FRED 
(hwnd-by-name 'fred) 
;; lookup hwnd with ID 1
(hwnd-by-id 1)
;; Lookup the name of the hwnd with ID 1 
(hwnd-name-by-id 1)

This makes it very simple to keep references to window handles in a consistent way rather than implementing private lists or globals in each program.

4. Examples

Various examples are provided which show various levels of abstractions and a good showcase of how to use it.

4.1 Zetcode samples

The rather comprehensive tutorial for the C programming language can be found here zetcode website. These have been translated to Lisp and show that the same GUIs can be written which correspond to largely the same structure.

4.2 Climage

This example GUI displays a two list boxes which show the packages and exported symbols. Clicking on a symbol displays the documentation for it.

In addition, this GUI shows how to write and handle modal dialogs and accelerator keys -- these are the keyboard combinations which are used as shortcuts for menu items. Ctrl+F brings up a Find dialog to search for a given symbol. Ctrl+Q quits.

4.3 Dragdrop

This shows how to support drag and drop functionality by handling the WM_DROPFILES message.

4.4 Pong

This is a small and not very well written example of how you might go about writing games. It's just a silly little pong game but shows the basic idea.

4.5 Icon

Shows how to add icons and other graphics.

4.6 Minesweeper

Simple minesweeper game.

4.7 Tetris

Simple tetris clone.

4.8 Macroman

Simple pacman clone. Shows how to reduce flicker by double buffering.

4.9 Scrollbar

How to add scrollbars and response to scoll messages.

4.10 Dragons: DNS client

This implements a simple DNS client using the DNS client dragons. Enter the DNS address in the IP address field, select the record type and entry name and click Query. The list box below is filled with the results returned from the server, or a message box indicates an error status.

4.11 RPC: MsgWaitForMultipleObjects example

This shows how to interleave networking and the message pump in the main thread, thereby making it possible to do asynchronous processing without blocking the gui. The example broadcasts to the rpcbind null procedure and fills in results as they are received. Requires frpc2. This means the gui never blocks, the same technique can be applied to do any networking, e.g. background refreshes of data. The examples uses RPC over UDP but there is no reason why you couldn't also do non-blocking TCP networking as well.

5. Notes

Requires CFFI. Developed on Windows 8.1 and Windows 7 using SBCL but should work on basically any Windows version because all the APIs are pretty stable and haven't changed for a long time. Should work with any Lisp implementation which provides FFI callbacks

5.1 TODO

  • Try with CCL, Lispworks etc.
  • Better error handling.

Licensed under the terms of the MIT license.

Frank James October 2016.


Common Lisp Win32 GUI library





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