I thought I post all needed informations about it. This is rather Lazarus problem than my code because code I use (from Lazarus Wiki) works:
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uses
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LResources, DefaultTranslator;
...
...
initialization
LRSTranslator := TPoTranslator.Create('/path/to/the/po/file');
I mean, I can translate my app with this perfectly.
The thing is I have a few components (TButton, TSpeedButton) which have several lines of Hint property (I made them with String Editor which is under [...] button. In Project Options->i18n I checked in "Enable i18n" option and set directory as "languages" which is in the same directory as my project, and also I have checked "Create/update .po file when saving a lfm file" option. When it creates this file it takes only first lines of Hint properties of this buttons.
For example, I have hint like this:
Delay activation of pipette/ruler
Range: 0-5 [sec]
In .lrt file I have something I want:
TFMAIN.TBPICKDELAY.HINT=Delay activation of pipette/ruler
Range: 0-5 [sec]
But in .po file I only get
msgid: Delay activation of pipette/ruler
msgstr:
So it's only the first line of it (missing "Range: 0-5 [sec]").