Saturday, May 12, 2007

Vista troubles

As anyone with even a tiny experience in upgrading from one OS to another would expect, going from Windows XP to Vista is not a trivial task. I installed Vista on one computer so that I could use it as a test-bed for upgrading my software ‘Viewbox’. Installation went fine except for the very frustrating fact that Vista Home Premium cannot be installed as an upgrade to XP Professional. You will need Vista Business or Ultimate to do that. So a clean install was done, requiring re-installation of a large number of software afterwards.
Then came the task of making Viewbox run on Vista (I already knew that Viewbox aborted on loading). I installed Delphi 2007 Professional and recompiled but the problem still persisted, flagging the error: ‘the computer does not have HTML Help support’. I knew this was not possible, because HTML Help support is built into Internet Explorer and depends on ‘hhctrl.ocx’, which is installed with Vista. The problem was that Viewbox could not find the ocx file. After a bit of googling, I found out that the file has changed location. If you want to find it, you should not rely on the registry entry, but you should look into the Windows folder. See the web page of The Helpware Group for more info.
However, even after solving this problem, Viewbox would not load. The problem was that I was using a TImageList component with a width of zero. Apparently, Windows XP has no problems with that, but Vista cannot tolerate it and shuts down the offending software. Fixing this was easy. Of course, you may ask why I was using a TImageList of zero width. That is another story.
After these changes, Viewbox seems to be running just fine under Vista. However, new security measures have been implemented in Vista. They include the User Account Control (UAC) system (for a detailed explanation, try this doc from Microsoft: WindowsVistaUACDevReqs.doc). The UAC does not allow writing of files in the C:\Program Files folder. This is a problem, because Viewbox saves its various settings in the Program Files\Viewbox folder as an INI file. I am not going to explain the details of the UAC (read the doc mentioned above). What you should know if you are programming in Delphi 2007, is that the XPManifest now includes an entry for the security level, as follows:
<trustInfo xmlns="urn:schemas-microsoft-com:asm.v3">
Setting ‘level’ equal to ‘asInvoker’ tells Vista not to implement virtualizing, so if your software tries to write to C:\Program Files\ it will fail. I have not figured out how to make Delphi change the Manifest contents so that virtualizing of files is possible.