JVCL FAQ

 JVCL: Frequently Asked Questions (FAQ)

JEDI Visual Component Library

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 Q What is the JVCL?

A The JVCL is a library of more than 500 visual and non-visual components for Delphi, C++Builder and Kylix. The components have been donated by developers from all around the world and can be used in commercial as well as shareware and freeware and open source projects without cost.

 Q Where can I get it?

A You can always download the latest release of JVCL from the JVCL homepage at http://jvcl.sf.net.
You can also get the JVCL from SVN or from the daily zips. See the JVCL Download page for more information.

 Q How is the JVCL licensed?

A The JVCL is licensed under the Mozilla Public License (MPL 1.1) license.

In short, the MPL allows you to use the JVCL components in commercial, shareware, freeware and open source projects as long as you give due credit to the JVCL in your application (including a notice in your About Box is a good idea).
If you extend, derive from or modify any unit in the JVCL, you are obliged to make the source of the modifications available to your customers. You are also encouraged to donate any modifications back to the JVCL community.

To learn more about the MPL, see Licensing.

 Q How can I contribute?

A There are several ways you can contribute to the development of JVCL. Among other things, you can write new or extend existing components, write help, fix bugs or write demos.

If you are a writer, you could write articles about the JVCL or about specific components in the JVCL. If you speak a foreign language (foreign to english speaking people, that is), you could help translate the JVCL to other languages.

For more information , see Contributing.

 Q Required Package 'Inet' Not Found

A From Julien Ferraro:
It's probably because you didn't choose to install the Internet components. Just launch your Delphi setup and select "Internet components" (or whatever the name is) and you should be OK.

 Q In D7, when I press F1, I am not getting JVCL help information

A Go to Help/Customize, delete the JCL.cnt and JVCL.cnt references, add them again, and save the project.

 Q When I try to compile my apps, I get an error message "line is too long (>1023 chars)"

A The files probably have UNIX carriage returns in them.
Use something like http://ccrma-www.stanford.edu/~craig/utility/flip/ to correct it.

 Q I'm getting an error ("Cannot load package JvNet. It contains zlib.pas which is also in package YYYY") when I try to install the JvNet package.

A Open the JvNet run-time package and add the other run-time package ("YYYY") to it's requires node. Try to install again.

 Q "The procedure entry point SHGetSpecialFolderPathA could not be located in XXX".

A You probably have an older Internet Explorer installed. Install the latest IE release.

You might also want to try to update your ComCtl32.dll.

Since Microsoft keep moving their pages around, we cannot give you a reliable link. Instead, go to Microsoft's website and search for 50comupd.exe.

 Q How do I dock a form at design-time with the JvDocking components?

A You can't dock the forms at design-time. You will have to do it programmatically.

 Q How do I change the docking style at runtime?

A You can't change it at runtime, only at design-time. We are working on resolving this issue.

 Q Cannot load JvMM. It contains VFW.pas which is also contained in GLSCENE.

A Resolve it by either adding the GLSCENE package to the requires of JVMM or add JvMM to the requires of GLSCENE. Rebuild the packages.

 Q Unit zlib/zlibconst implicitly imported into JvCrypt

A This message is nothing to worry about unless you have other packages also including zlib. In that case, you

might get an error saying something like: "Unable to load JvCrypt. It contains unit zlib which is also included in package XXXX".
The error message is not entirely correct but nevertheless you cannot install two packages that includes (explicitly or implicitly) the same units. To resolve, you have to add the other package's dcp file to the requires node of JvCrypt and rebuild JvCrypt.
In some cases, this doesn't help either because the other package is using a non-standard zlib unit (JvCrypt requires the standard zlib/zlibconst.pas available on the Delphi CD). To resolve this issue, you can copy the Borland zlib and zlibconst unis from the Delphi CD to your computer and rename them (you will also need the obj files in the same folder). Open JvZLibMultiple.pas and change the uses clause to reflect the name of the renamed Borland zlib unit).

If all else fails, remove JvZLibMultiple.pas from the JvCrypt runtime package and the JvZLibMultiple registration and uses from jvcl\design\JvCryptReg.pas and rebuild the packages (runtime as well as design-time).

 Q Why doesn't JvDotNetFilenameEdit and JvDotNetDirectoryEdit have a palette icon?

A If the package containing JvFilenameEdit and JvDirectoryEdit is installed after the JvDotNet package, the icons won't be shown on the palette.

Fix:

• In Delphi, go to Component - Install Packages
  
• Select the Jv DotNet package in the list
  
• Toggle the checkbox off and then on again
  
• Close the dialog

 Q After installing JVCL, my palette icons are corrupted.

A This error can be caused by faulty video drivers or an old version of the common controls library.

Fix:

• Get the latest Internet Explorer release from Microsoft. It will update the ComCtrl library as well.
  
• If that doesn't help, try to find updated video drivers for your graphics card.
  
• If it still doesn't help, try lowering the video acceleration (you do this from Control Panel-Desktop-Settings-Advanced).

 Q Will JVCL continue to support and develop RXLib?

A Yes, we will continue to support and develop RXLib but within the constraints of JVCL. This means that RXLib components can be merged, replaced, archived and renamed at any time as we see fit (indeed, this has already happened to a few of the original RXLib components).

JVCL will try to preserve backward compatibility, taking into account the cost for JVCL (maintenance, stopping of future development, not being able to fix bugs etc). If we think it is better for the JVCL as a whole to make changes that break backward compatibility, we will do the changes.

This standpoint is not RXLib specific. We reserve the right to do the same with any library or component donated to JVCL.

 Q C++ Builder: Why isn't anything updated when I use the '<<' or '>>' operator on a Set property (Font.Style, JvWizard.EnabledButtons...)

A This is a BUG in C++ Builder related to the way the '<<' and '>>' operators work, as reported in Quality Central under bug #9359. For instance, if you want to add "fsBold" to the Font style, the following code is not reliable.

Font->Style << fsBold;

Use that one instead:

Font->Style = TFontStyles(Font->Style) << fsBold;

This is the only way you can be sure that the internal value will be set AND the property setter, if any, will be called.