Introduction to CLX

Charlie Calvert

Overview

• What is CLX?
• What is Qt?
• Why Qt?
• How does X Windows work?
• What is in and out?
• Events and signals

What Is CLX?

• CLX is a set of platform independent components
• CLX is divided into several parts
• BaseCLX - base CLX, system, SysUtils, classes, etc.
• VisualCLX – visual components - based on Qt
• DataCLX – database components - based on dbExpress and MIDAS
• NetCLX – WebBroker, InternetExpress, …

What is CLX?

• What Is Qt?
• A platform independent C++ class library built to run under windows and X Windows
• The C++ class library that is most prevalent under Linux and is used for KDE, the most popular desktop
• Qt licensing models
• No license for Delphi based CLX projects
• Open source for open source projects
• Qt under Linux is Open Source for Open Source projects.
• For more information go to www.trolltech.com

Why use Qt instead of GTK, etc.

• Qt was closer to Windows style of development than GTK
• Qt graphics model was closer to VCL graphics model
• Painter (similar to Canvas), Font, Pen, Brush objects
• Qt supported KDE better than GTK
• We felt using Qt would be quicker than adapting GTK to VCL
• Had to adapt to Qt’s C++ API
• Utilities create Delphi bindings from Qt header files
• MOC (meta object compiler) – generates RTTI for Qt
• VisualCLX Handles and Hooks

How Do I Get Qt?

• Qt free edition - a QPL version is available for download at www.Trolltech.Com
• Documentation is also available at www.trolltech.com

What Makes Qt Special?

• Qt classes look very much like VCL components
• Properties appear as get/set method pairs (e.g. caption/setCaption).
• Events appear as signals
• Events are user created
• Signals are component created
• VCL merges the two
• Qt introduces many standard controls Called widgets
• Qt handles the message loop

What Makes Qt Special?

• Qt uses the X Window library
• Windows are X handles
• Graphics contexts are X graphic handles
• Qt uses the windows API under windows
• Very good C++ class library
• Some classes not wrapped
• Dictionaries, lists, maps, …
• Classes are very component like

How X Differs From Windows

• X separates an application into
• The client (the code you write)
• The server (the display)
• Physical separation of UI from application
• Separation introduces performance issues
• All display commands go through TCP/IP
• X11 Architecture

What Is New to VisualCLX

• VisualCLX will use Qt for 80% of its widget implementation
• VisualCLX uses handles and hooks
• VisualCLX will introduce styles
• A new way of doing “owner” draw
• You can create your own styles
• Ties into Linux themes

Events and Signals

• Events are translations of X user events (key press, mouse move, paint, etc).
• Signals are component defined “events”, corresponding to VCL events (OnClick, OnChange, etc).
• Hooking Events requires a special hook object

Porting to CLX

• What Components are you using
• Use VCL Scanner
• Check with 3rd Party component vendors for availability
• Examine custom components
• Examine your application for Windows dependencies
• Windows API
• File case sensitivity, etc.
• Determine API availability

Porting custom components to CLX

• Expect more differences
• Look for Windows API calls
• Use VCL wrappers
• TCanvas, TBitmap, etc.
• MouseDown, MouseMove, etc.
• Create your own abstractions
• Start changing the components today
• Rule of thumb: If the API came from Microsoft, it probably will not be on Linux

What is out?

• Messages and message directive (Still supported by the compiler)
• WinAPI (Windows.pas etc.)
• COM/ActiveX/OLE
• Use dynamic methods
• Recreate window handle logic (not needed)
• Setting some windows attributes when window handle existed
• Out of the first release
• Docking (in the first release)
• Docking – not in 1st version
• BiDi (bi-directional mode) – not in 1st version?
• IME (input method editor) – not in 1st version?

What is different?

• Many messages are now dynamics
• Broadcasts – parent font – may keep messages
• Unit names, locations of some classes
• Class names and hierarchy mostly unchanged
• Q(unit name) – QControls, QComCtrls
• Property editors mostly unchanged
• Owner draw and Styles
• .dfm extension will change for CLX
• .dfm for windows, .xfm? for Linux
• Format will be the same (text and binary)
• This is done to help to create single source applications

What is the same?

• TCanvas
• The class hierarchy
• TControl, TWidgetControl (rename of TWinControl) TForm, TScrollingWidget (rename of TScrollingWinControl).
• MouseDown, MouseMove, KeyDown, etc.
• BaseCLX (Classes, etc.)