Upgrading to Delphi 2010

While the next major release of the application I work on will no doubt be written in C# (unless we get a 64-bit Delphi, then I have something to argue my case with), for the short-term, we will continue using Delphi. To that end, I like to keep up with the latest version (not always sure that’s a good idea, but anyway) so we recently got a copy of Delphi 2010 to see how easy the upgrade would be.

Not so long ago, I moved from Delphi 2006 to Delphi 2009, so I thought this upgrade would be a walk in the park. There should be no breaking changes. I would need to change a few defines, but that’s about it. And initially that was the case. In no time at all, I had upgraded our third-party components, made the necessary changes to include the new compiler version (more about that in a later post perhaps), and I had the whole thing building in no time. I ran it and disaster. Well it seemed like a disaster. All the fonts of all the menus, both the main menu and all popups were both the wrong font, very large (some the size of the monitor) and skewed. I checked the components in question, and yes the font property was basically garbage. I checked the DFM file, and everything was correct.

Now I have to add that we use some old DevExpress components for our menus. We never upgraded them as they did a complete rewrite of their grid component at the same time, and we had too much invested in the old one. Anyway, we have faithfully updated the source as and when needed. The unicode changes were perhaps the biggest challenge, but not too difficult. Now this! What was wrong?

Something was changing the font. I delved into the source for the components, and zeroed in on the following few lines.

var
  NonClientMetrics: TNonClientMetrics;
begin
  NonClientMetrics.cbSize := SizeOf(TNonClientMetrics);
  SystemParametersInfo(SPI_GETNONCLIENTMETRICS, 0, @NonClientMetrics, 0);
  Font.Handle := CreateFontIndirect(NonClientMetrics.lfMenuFont);
  ...

Now this code hasn’t changed since we compiled it with Delphi 2009, so I delved into windows.pas, and found the record that TNonClientMetrics ultimately points to tagNONCLIENTMETRICSW and down at the end, the following line.

iPaddedBorderWidth: Integer; //Requires Windows Vista or Later

Aha, I’m working on Windows XP. I checked the same record in Delphi 2009, and that line was missing. So sizeof was returning 4 bytes extra in Delphi 2010 than it did in Delphi 2009. I confirmed this by trying the following

NonClientMetrics.cbSize := SizeOf(TNonClientMetrics) - SizeOf(NonClientMetrics.iPaddedBorderWidth);

Yes, everything back to normal. Obviously, the code should check for windows version and return the size accordingly, but some kind soul has done that work for me, and added a static method, sizeof, to the record. So the code becomes

NonClientMetrics.cbSize := TNonClientMetrics.SizeOf;

The sizeof static method checks windows version and adds or removes the extra 4 bytes accordingly. I hate breaking changes like these, but whose fault was it. Delphi 2010 or Microsoft?