[SOLVED] Correct way to pass ordinary String to WinAPI Unicode functions

[furious programming]

There are at least few ways to convert standard String variable and pass the result as a PWideChar to Windows API functions with postfix W. But I am looking for a solution that is, above all, correct, short and will work without any problems on modern Windows (especially Windows 10) and using the OBJFPC mode.

So, in my program I store all strings as a standard String type. Now I need to pass two such strings to the ShellExecuteW function. These strings are to include the directory path and the file name. The function is to open a given directory in the file explorer and highlight the given file (setting lpOperation to explore). What is the correct way to pass such a strings to ShellExecuteW function?

Thanks for any suggestions.

[ASerge]

There are at least few ways to convert standard String variable and pass the result as a PWideChar to Windows API functions with postfix W. But I am looking for a solution that is, above all, correct, short and will work without any problems on modern Windows (especially Windows 10) and using the OBJFPC mode.

So, in my program I store all strings as a standard String type. Now I need to pass two such strings to the ShellExecuteW function. These strings are to include the directory path and the file name. The function is to open a given directory in the file explorer and highlight the given file (setting lpOperation to explore). What is the correct way to pass such a strings to ShellExecuteW function?

Use UnicodeString:

Code: Pascal  [Select][+][-]

1. {$MODE OBJFPC}
2.  
3. uses Windows, ActiveX, ShellApi;
4.  
5. procedure SelectFileInExplorer(const FileName: string);
6. var
7.   Params: UnicodeString;
8. begin
9.   Params := ' /select, ' + UTF8Decode(FileName);
10.   ShellExecuteW(0, nil, 'explorer.exe', PWideChar(Params), nil, SW_SHOW);
11. end;
12.  
13. begin
14.   SetMultiByteConversionCodePage(CP_UTF8); // Lazarus compatible
15.   CoInitializeEx(nil, COINIT_APARTMENTTHREADED or COINIT_DISABLE_OLE1DDE);
16.   SelectFileInExplorer('c:\Windows\system.ini');
17. end.

[Aidex]

I use this line ...

Code: Pascal  [Select][+][-]

1. SysUtils.ExecuteProcess(UnicodeString('explorer.exe'),UnicodeString('/select,"'+fn+'"'),[]);  
2.  

[Remy Lebeau]

I use this line ...

Code: Pascal  [Select][+][-]

1. SysUtils.ExecuteProcess(UnicodeString('explorer.exe'),UnicodeString('/select,"'+fn+'"'),[]);  
2.  

Are the typecasts really necessary?  ExecuteProcess() is overloaded for RawByteString and UnicodeString, so if the type-casts are removed:

Code: Pascal  [Select][+][-]

1. SysUtils.ExecuteProcess('explorer.exe', '/select,"'+fn+'"', []);  
2.  

Then, if String is a (UTF-8 encoded) AnsiString then the RawByteString overload will be called, otherwise String will be UnicodeString so the UnicodeString overload will be called instead.

[Aidex]

The Unicode typecast is not necessary.
I only use it because I saw in the Windows specific sourcecodes of FreePascal that there is always a typecast to Unicode done internally.
Therefore I got used to use UnicodeString for paths and filenames if possible. At least under Windows it is no disadvantage, I think.
Since in my other source codes the filename is already defined as UnicodeString, I did so.

[furious programming]

To this day, I have used two ways to convert — one was:

Code: Pascal  [Select][+][-]

1. PWideChar(UnicodeString(MyString))

and the other was:

Code: Pascal  [Select][+][-]

1. PWideChar(UTF8ToUTF16(MyString))

Both worked, without any extra things. But I found it strange that the same conversion (regular String to PWideChar) could be solved in different ways. It seemed to me that they are not unambiguous. And now @ASerge gave another one, this time using the UTF8Decode function and UnicodeString as a temp variable (and other initialization functions, which is more complex that simple casting/converting).

Actually all these ways are correct?

Ultimately, I used ExecuteProcess because it allows me to skip the conversion (there is a version for RawByteString), and secondly, I can open the directory in the file explorer and additionally select the file, if it should be selected. The only problem is that I can't select multiple files this way — I tried various ways to use the /select parameter, but it didn't do anything.

Anyone have an idea how to open a directory in the system file explorer and highlight a few files? Is such a thing possible?

[ASerge]

Anyone have an idea how to open a directory in the system file explorer and highlight a few files? Is such a thing possible?

See SHOpenFolderAndSelectItems.

[furious programming]

Ok, thanks for the reply. But in my project this is additional feature, so I will consider its implementation. Thank you all for help, problems solved.