UI: Become windowless

A request on the Yahoo WTL newsgroup and a blog-article sparked some interest to look closer at creating a windowless user-interface. Traditionally, Windows applications are built upon the GDI/User windowing hierarchy, and thus restricted in several areas. While you can certainly generate a nice application quickly with the built-in control-set and get a standard clean look, you will soon enough stumble upon the limitations of the Windows controls - especially if you want to build something that looks a little more flashy. The native Win32 custom-draw/owner-draw technique is limited, next to no support for transparent windows, rigid control scaling/resizing and the Common Controls are merely remnants of Windows Explorer, Office or Internet Explorer widgets.

A windowless user-interface doesn't make use of the native Win32 controls. Instead it custom paints every control and widget on the screen - including labels, buttons, list control, etc. etc. Variations of this kind of interface is not new: "Skinning" has been widely accepted for its cool application-look, as seen in Nullsoft's WinAmp and the MS Media Player. But skinning is usually only feasible for small applications hosting a limited number of dialogs. If you're building a large database-driven application, you'll want to have a solid framework to back your dialog design up.

So I was looking at the Microsoft CRM application. In my opinion, this is one of the most successful DHTML interfaces I've seen (I should know because I've previously been assigned on a large browser-based CRM product). The MS CRM interface looks very Windows XP-like, but it also has several cool features, such as a navigation bar, a highly flexible list control and several shaded/gradient tool panels. I thought this would be a nice look to build for my windowless framework. I've previously tested a DHTML interface with this look, but wasn't satisfied - mostly because integrating with the browser (IE) was painfully complicated.

Direct UI sample Even if constructing a windowless user-interface is a lot of hard work, it pays off in the end. But you do need to implement your own dialog builder, button-design, keyboard interface and lots of little things you take for granted. Actually it's not the painting of buttons and toolbars that take the most planning and effort; it's supporting keyboard shortcuts, tab-navigation, automatic tooltips and a scalable design. And then there are the mandatory - but often overlooked - features, such as list column-sorting, intuitive focus changes and overflow scrolling that need to be addressed.

The design

My Direct UI user-interface takes bits and pieces from other UI models. Specifically it borrows ideas of the "controls-inside-controls" design from the Java AWT framework, XML dialog-resources from .NET, event-bubbling from DHTML and C++ helper classes from MFC.

The code doesn't actually use the WTL library like most of my other user interface samples on this website. It's pure Win32 calls.
One of the requirements for the framework was that it could be placed in an external DLL. This had a nasty impact on the design, because C++ templates are not by any sane method exportable in a DLL. So, a clean C++ old-skool (MFC) design is enforced, with single inheritance and few (if not none) macros.
A window is built by nesting controls inside each other. Some controls are containers (such as the ToolBar, which contains ToolButtons). To insert a ToolBar button, you simply construct a CToolButton C++ class and add it to the CToolPanel control container. Most containers define layout algorithms such as the vertical layout-panel, which arranges the contained elements below each other - a feature known from Java AWT.

Using a Java-like design, such as the layout containers, make sure that your controls will rescale automatically when the window is resized. But anyone who has done any Java development knows how limiting its control layout features are and has wished to kick the authors of the GridBagLayout class in the nuts. So there's also room for a dialog layout-panel, which allows you to put controls at a fixed position, but with the option of scaling based on various stretching rules.
Constructing an entire window by hand is tedious, so there's a small XML parser included (extremely fast, extremely non-compliant) which parses and builds a window from an XML string.
The framework caches all of its Win32 brushes and pens. Most of the GDI resources saved on window handles are probably spent on this. But these kinds of objects are light-weight; it's the paint job that gets an incredible overhaul.
Native Win32 controls are used only for the EDIT control. This control contains so much functionality that it would take ages to do a decent replacement. Single-line edit controls are created on the fly (when you click on the frame) and multi-line edits are always visible. So the framework does have the ability to embed native Win32 controls and even ActiveX controls, but at the expense of screen flickering and severe restrictions in the visual effects I'm planning.

Alluring text

The real benefits of this type of interface are the simple things. For instance, you can with one single swoop replace all occurences of Win32 DrawText() with DrawPrettyHtmlFormattedText() - which instantly gives you icons, customizable text-colors and clickable hyperlinks in the entire user-interface. With one single line of code, you can now add HTML links in the statusbar panel.
Similar, you are not restricted to only put CToolButton controls inside the ToolBar. Any kind of control can be added. This also goes for the list control, which quickly can be made cool by adding some group-labels, or just by adding buttons or HTML links. Since the individual controls rarely erase the background, most of them will actually fit transparently inside the other container controls, so once you've made a neat widget it can be reused in the entire user interface.

3D Animations

Another cool effect that can be easily added is the ability to do 3D rendering directly on the canvas. Just throw in some DirectX calls and you'll be able to write cool page transitions, highlight a control with some cool sparkling particle-effect or just put some glow effect on the edit-box with focus.
You can also read about how I integrated DirectX into the application.

The sample

This may all sound very nice. However, the sample presented here is just the initial stage of a windowless framework I'll use for further testing. The library will need to mature a bit and go through a few rewrite cycles before I'll attempt to actually incorporate it in a real application. Still, it's pretty functional already. Enjoy.

The sample should be run with DirectX 9 installed and a modern 3D graphics card. Otherwise you will not be able to view the pretty 3D animations.

Source Code Dependencies

Microsoft Visual C++ 6.0
Microsoft DirectX 9 SDK

Download Files

Demonstration (91 Kb)
Source Code (126 Kb)

Article submitted 6/26/2005.
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