[Lazarus] Cross-platform using TRegistry - how to?

Tony Whyman tony.whyman at mccallumwhyman.com
Mon May 4 11:25:42 CEST 2020

Firstly, the question is about TRegistry and not TRegIniFile. On a *nix 
platform TRegistry is implemented using TXMLRegistry and not TRegIniFile.

You should only have a single instance of a TXMLRegistry in any one 
program no matter how many times you create a TRegistry object - they 
all point to the same instance. From a quick check of the code, it looks 
like the problem identified in the bug reportĀ  is fairly obvious - the 
current key state is held in TXMLRegistry rather than TRegistry. The fix 
should be to hold the current key state in TRegistry and call 
TXMLRegistry.SetKey before every get or put call on TXMLRegistry (from 

TRegistry is a very useful way of saving dynamic configuration data 
(e.g. mainform co-ordinates) in order to preserve them from one program 
session to another - and to do so in a cross-platform manner. IMHO. it 
would be a significant loss if it was to be deprecated. I use it all the 

As to the filename issue: the xml file location is determined from the 
Vendor Name and application name and relative to $HOME/.config - is that 
really a problem?

TXMLRegistry writes are normally flushed to disk after every write. Two 
program instances using the same registry keys can get in each other's 
way with one over-writing the other's updates - but then that is also 
true of .conf and .ini files - and even the Windows registry.

On 04/05/2020 08:29, Bart via lazarus wrote:
> On Mon, May 4, 2020 at 12:41 AM Bo Berglund via lazarus
> <lazarus at lists.lazarus-ide.org> wrote:
>> structure:
>> HKLM\SOFTWARE\Companyname\Applicationname\Server\(named values)
>> HKLM\SOFTWARE\Companyname\Applicationname\Configuration\(named values)
> The *nix way is to use .conf files (basically ini-files) for that.
> IIRC you have no control over where the xml file (with the registry
> keys) is placed.
> There are some issues with the xml implementation of the registry.
> Most important: TRegIniFile is completely broken and as of 3.2
> deprecated on non-windows platforms.
> Also, when you have 2 keys opened at the same time, reading/writing
> may go to/from the wrong key:
> https://bugs.freepascal.org/view.php?id=36842
> For a cross-platform application I wouldn't use TRegistry myself.
> Bart

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