1. Computing

Store User and Application Data in the Correct Location

Get Known Folder Path using Delphi

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User / System Special Paths

User / System Special Paths

When in the need of storing some content related to your Delphi application on the user's hard disk, you should take care of the support for state separation of user data, user settings, and computer settings.

For example, The "Application Data" folder in Windows should be used to store application specific documents such as INI files, application state, temp files or similar.

You should never use hard-coded paths to specific locations, such as "c:\Program Files", as this may not work on other versions of Windows because the location of folders and directories can change with different versions of Windows.

The SHGetFolderPath Windows API function

The SHGetFolderPath is available in the SHFolder unit. SHGetFolderPath retrieves the full path of a known folder identified.

Here's a custom wrapper function around the SHGetFolderPath API to help you get any of the standard folders for all or the currently logged Windows user.

 uses SHFolder;
 
 function GetSpecialFolderPath(folder : integer) : string;
 const
   SHGFP_TYPE_CURRENT = 0;
 var
   path: array [0..MAX_PATH] of char;
 begin
   if SUCCEEDED(SHGetFolderPath(0,folder,0,SHGFP_TYPE_CURRENT,@path[0])) then
     Result := path
   else
     Result := '';
 end;
 
Here's an example of using the SHGetFolderPath function:
  • Drop a TRadioButtonGroup (name: "RadioGroup1") on a form
  • Drop a TLabel (name: "Label1") on a form
  • Add 5 items to the radio group:
    1. "[Currenty User]\My Documents"
    2. "All Users\Application Data"
    3. "[User Specific]\Application Data"
    4. "Program Files"
    5. "All Users\Documents"
  • Handle the RadioGroup's OnClick event as:

Note: "[Current User]" is the name of the currently logged in Windows user.

 //RadioGroup1 OnClick
 procedure TForm1.RadioGroup1Click(Sender: TObject) ;
 var
   index : integer;
   specialFolder : integer;
 begin
   if RadioGroup1.ItemIndex = -1 then Exit;
 
   index := RadioGroup1.ItemIndex;
 
   case index of
     //[Current User]\My Documents
     0: specialFolder := CSIDL_PERSONAL;
     //All Users\Application Data
     1: specialFolder := CSIDL_COMMON_APPDATA;
     //[User Specific]\Application Data
     2: specialFolder := CSIDL_LOCAL_APPDATA;
     //Program Files
     3: specialFolder := CSIDL_PROGRAM_FILES;
     //All Users\Documents
     4: specialFolder := CSIDL_COMMON_DOCUMENTS;
   end;
 
   Label1.Caption := GetSpecialFolderPath(specialFolder) ;
 end;
 
Note: The SHGetFolderPath is a superset of SHGetSpecialFolderPath.

You should not store application-specific data (such as temporary files, user preferences, application configuration files, and so on) in the My Documents folder. Instead, use an application-specific file that is located in a valid Application Data folder.

Always append a subfolder to the path that SHGetFolderPath returns. Use the following convention: "\Application Data\Company Name\Product Name\Product Version".

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