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Home: Development: Papers

Delphic mysteries

Any large and complex tool is bound to have hidden nooks and crannies and Delphi 5 is no exception.

Delphi 5 sports a new set of flamboyant marketing features with names like ADO Express, InterBase Express, and Internet Express -- the perfect complement to my daily dose of Italian espresso. The new Delphi also offers an updated IDE, international support, TeamSource, the Data Module Designer, the ApplicationEvents component, the OnContextMenu event, and an updated version of MIDAS. These and many other features are carefully listed in the Delphi 5 "What's New" on-line help page.

Although the list of the new features described in the on-line marketing literature and technical documentation is large, not every new feature is listed there. Some secrets are documented but hard to find and others are almost completely undocumented. However, we have the source code, so nothing is totally undocumented -- except the proxies unit. Some of these features have been discussed elsewhere and this is far from a complete list. But these are my favorite new secrets.

Navigational aids

The new Object Inspector has many great features -- some of them not obvious. For example, wherever a property refers to a component you can now Ctrl-double-click on the property value (the referenced component) to load the other component into the Object Inspector. This is a handy way of moving from one component to another linked one. This is similar to the Ctrl-click navigation offered in the editor since Delphi 4. 

You probably know that Delphi 5's Object Inspector includes graphical drop down lists. Besides cursors, images, and other graphical elements, you can tune the IDE to display a graphical drop down list of fonts, instead of a plain one.

Unfortunately, there isn't an Environment Option to turn on this feature -- not even an undocumented registry setting. To use the feature you need to create a package, and add a unit that sets a global Boolean variable to True in the unit's initialization section. The variable, FontNamePropertyDisplayFontName, beats TwoDigitYearCenturyWindow in the longest variable name contest. The code to make it work is extremely simple and is sort of documented. There is a source code comment describing this property buried in the 4k lines of the DsgnIntf unit. The associated comment warns "Enable it at your own risk," as this can affect the rendering operation on a slow computer with hundreds of fonts installed. 

The VCL also has many new features. One, which is fully described, is the new FreeAndNil procedure that frees the object passed to it as a parameter and sets the reference to nil. At the opposite end of the documentation spectrum, there is almost no mention of the new GetPropValue function of the TypInfo unit (a unit that was heavily updated in the Delphi 5 release). You call this function with a component and the name of a property of the component; it returns a variant with the property's value:

strBtnCaption := GetPropValue (Button1, 'Caption'); 

Optionally you can pass a third parameter to get a textual description of a setting instead of its actual value. In the TypInfo source code you'll find a reasonable amount of information, and, again, an example might help you figure out how to use the function. The example includes the more complex code (now commented out) required in past versions of Delphi to achieve the same effect.

Menu mania

There are new features related to menu captions and accelerator keys. Delphi 5 can add accelerator keys to menus when you forget to include the ampersand, or when two accelerator keys are conflicting -- something hard to determine if you create the menu dynamically. This capability is set using the AutoHotkeys property. Note that AutoHotkeys is on by default and can cause problems if your program relies on the text of the captions. Along with these new features, the Menus unit includes two new global routines, StripHotkeys and GetHotkey. These are fully described in the help files. The individual menu items and submenus can have specific ImageLists connected, so you don't need a single image list for the entire menu.

You might not have noticed that there are new default actions for the ActionList component. These actions are mainly related to help operations but also offer some new edit actions.

The new TMask class defined in the masks unit (not to be confused with the mask unit, which has no final s) allows the comparison of strings with wildcards. The mechanism is quite powerful, but Borland managed to hide this new feature in the TMask.Create VCL help entry.

I like one additional VCL feature a lot: main forms now behave properly when minimized and restored. With Delphi 5, applications now show the Windows animation effects and produce the associated system sounds. Although the sounds were easy to code in Delphi 4, the animation was difficult. This is not the only new feature related to Windows support. The common controls have been updated and menu items are now Windows 2000-ready.

This is far from a complete list of Delphi 5 secrets. (I mentioned you can type Alt+JEDI in the about box in my IDE article.) Borland is certainly doing a better job of listing new features and providing complete and readily available help files than it has in the past. There is now a list of units, each with a list of routines and classes. And the categorized list of routines -- missing since Delphi 1 -- has resurfaced. Additionally, the source code includes many property editors and designers. Fortunately for those of us who write articles and books, however, something always seems to slip by. I should mention that a lot of these features were shared with me by members of the Delphi R&D team. 

If you haven't upgraded to Delphi 5 yet, I have a list of Delphi 4 hidden features which are still undocumented -- including the hidden registry settings. And if you've discovered other hidden Delphi 5 features send them my way and I'll spread them to the rest of the community.

Originally written for InPublishing LLC for publication by Inprise Corp. Copyright 1999 Inprise Corp.