How to get icon and description from file extension using Delphi? - windows

Question

Basically I have a TcxGrid which will be listing various files names and I'd like to give further details based on the file extension, specifically it's description (e.g. for .PDF it's "Adobe Acrobat Document") and it's related icon.
I notice there is a very similar question already but it's C# related and I'd like something Delphi based.
Suggestions on where to look for this kind of info would be good and if there is a class similar to the one mentioned in the C# post above (obviously in Delphi) that would be great.

Answer 1

Thanks to Rob Kennedy for pointing me in the direction of ShGetFileInfo. I then Googled on that and found these two examples - Delphi 3000, Torry's. From that I wrote the following class to do what I needed.
Also, just as I was finishing up Bill Miller's answer gave me the final bit of help I needed. Originally I was passing full file names through to ShGetFileInfo, which wasn't ideally what I wanted. The tweak suggested of passing "*.EXT" was great.
The class could do with more work but it does what I need. It seems to handle file extensions that have no details associated either.
Finally, in what I'm using I've switched it to using a TcxImageList instead of a TImageList, since I was having problems with black borders appearing on the icons, because it was a quick fix.
unit FileAssociationDetails;
{
Created : 2009-05-07
Description : Class to get file type description and icons.
* Extensions and Descriptions are held in a TStringLists.
* Icons are stored in a TImageList.
Assumption is all lists are in same order.
}
interface
uses Classes, Controls;
type
TFileAssociationDetails = class(TObject)
private
FImages : TImageList;
FExtensions : TStringList;
FDescriptions : TStringList;
public
constructor Create;
destructor Destroy; override;
procedure AddFile(FileName : string);
procedure AddExtension(Extension : string);
procedure Clear;
procedure GetFileIconsAndDescriptions;
property Images : TImageList read FImages;
property Extensions : TStringList read FExtensions;
property Descriptions : TStringList read FDescriptions;
end;
implementation
uses SysUtils, ShellAPI, Graphics, Windows;
{ TFileAssociationDetails }
constructor TFileAssociationDetails.Create;
begin
try
inherited;
FExtensions := TStringList.Create;
FExtensions.Sorted := true;
FDescriptions := TStringList.Create;
FImages := TImageList.Create(nil);
except
end;
end;
destructor TFileAssociationDetails.Destroy;
begin
try
FExtensions.Free;
FDescriptions.Free;
FImages.Free;
finally
inherited;
end;
end;
procedure TFileAssociationDetails.AddFile(FileName: string);
begin
AddExtension(ExtractFileExt(FileName));
end;
procedure TFileAssociationDetails.AddExtension(Extension : string);
begin
Extension := UpperCase(Extension);
if (Trim(Extension) <> '') and
(FExtensions.IndexOf(Extension) = -1) then
FExtensions.Add(Extension);
end;
procedure TFileAssociationDetails.Clear;
begin
FExtensions.Clear;
end;
procedure TFileAssociationDetails.GetFileIconsAndDescriptions;
var
Icon: TIcon;
iCount : integer;
Extension : string;
FileInfo : SHFILEINFO;
begin
FImages.Clear;
FDescriptions.Clear;
Icon := TIcon.Create;
try
// Loop through all stored extensions and retrieve relevant info
for iCount := 0 to FExtensions.Count - 1 do
begin
Extension := '*' + FExtensions.Strings[iCount];
// Get description type
SHGetFileInfo(PChar(Extension),
FILE_ATTRIBUTE_NORMAL,
FileInfo,
SizeOf(FileInfo),
SHGFI_TYPENAME or SHGFI_USEFILEATTRIBUTES
);
FDescriptions.Add(FileInfo.szTypeName);
// Get icon and copy into ImageList
SHGetFileInfo(PChar(Extension),
FILE_ATTRIBUTE_NORMAL,
FileInfo,
SizeOf(FileInfo),
SHGFI_ICON or SHGFI_SMALLICON or
SHGFI_SYSICONINDEX or SHGFI_USEFILEATTRIBUTES
);
Icon.Handle := FileInfo.hIcon;
FImages.AddIcon(Icon);
end;
finally
Icon.Free;
end;
end;
end.
Also here is an example test app using it, it's very simple, just a form with a TPageControl on it. My actual use was not for this, but for with a Developer Express TcxImageComboxBox in a TcxGrid.
unit Main;
{
Created : 2009-05-07
Description : Test app for TFileAssociationDetails.
}
interface
uses
Windows, Forms, FileAssociationDetails, Classes, Controls, ComCtrls;
type
TfmTest = class(TForm)
PageControl1: TPageControl;
procedure FormShow(Sender: TObject);
procedure FormClose(Sender: TObject; var Action: TCloseAction);
private
{ Private declarations }
FFileDetails : TFileAssociationDetails;
public
{ Public declarations }
end;
var
fmTest: TfmTest;
implementation
{$R *.dfm}
procedure TfmTest.FormShow(Sender: TObject);
var
iCount : integer;
NewTab : TTabSheet;
begin
FFileDetails := TFileAssociationDetails.Create;
FFileDetails.AddFile('C:\Documents and Settings\...\Test.XLS');
FFileDetails.AddExtension('.zip');
FFileDetails.AddExtension('.pdf');
FFileDetails.AddExtension('.pas');
FFileDetails.AddExtension('.XML');
FFileDetails.AddExtension('.poo');
FFileDetails.GetFileIconsAndDescriptions;
PageControl1.Images := FFileDetails.Images;
for iCount := 0 to FFileDetails.Descriptions.Count - 1 do
begin
NewTab := TTabSheet.Create(PageControl1);
NewTab.PageControl := PageControl1;
NewTab.Caption := FFileDetails.Descriptions.Strings[iCount];
NewTab.ImageIndex := iCount;
end;
end;
procedure TfmTest.FormClose(Sender: TObject; var Action: TCloseAction);
begin
PageControl1.Images := nil;
FFileDetails.Free;
end;
end.
Thanks everyone for your answers!

Answer 2

Call ShGetFileInfo. It can tell you the description (the "type name," in that function's vocabulary), and it can give you an icon handle, or a handle to the system image list, where the icon resides, or the path to the module that holds the image resource. That function can do lots of different things, so make sure to read the documentation carefully.
MSDN says ShGetFileInfo "may be slow" and calls the IExtractIcon interface a "more flexible and efficient" alternative. But the sequence it recommends is to use an IShellFolder interface, then call GetUIObjectOf to get the file's IExtractIcon interface, and then call GetIconLocation and Extract on it to retrieve the icon's handle.
For all I know, that's exactly what ShGetFileInfo does anyway, but it's much more cumbersome, and after you've done all that, you still wouldn't have the file's type description. Stick with ShGetFileInfo until speed and efficiency become a noticeable problem.

Answer 3

function GetGenericFileType( AExtension: string ): string;
{ Get file type for an extension }
var
AInfo: TSHFileInfo;
begin
SHGetFileInfo( PChar( AExtension ), FILE_ATTRIBUTE_NORMAL, AInfo, SizeOf( AInfo ),
SHGFI_TYPENAME or SHGFI_USEFILEATTRIBUTES );
Result := AInfo.szTypeName;
end;
function GetGenericIconIndex( AExtension: string ): integer;
{ Get icon index for an extension type }
var
AInfo: TSHFileInfo;
begin
if SHGetFileInfo( PChar( AExtension ), FILE_ATTRIBUTE_NORMAL, AInfo, SizeOf( AInfo ),
SHGFI_SYSICONINDEX or SHGFI_SMALLICON or SHGFI_USEFILEATTRIBUTES ) <> 0 then
Result := AInfo.iIcon
else
Result := -1;
end;
function GetGenericFileIcon( AExtension: string ): TIcon;
{ Get icon for an extension }
var
AInfo: TSHFileInfo;
AIcon: TIcon;
begin
if SHGetFileInfo( PChar( AExtension ), FILE_ATTRIBUTE_NORMAL, AInfo, SizeOf( AInfo ),
SHGFI_SYSICONINDEX or SHGFI_SMALLICON or SHGFI_USEFILEATTRIBUTES ) <> 0 then
begin
AIcon := TIcon.Create;
try
AIcon.Handle := AInfo.hIcon;
Result := AIcon;
except
AIcon.Free;
raise;
end;
end
else
Result := nil;
end;

Answer 4

uses ShellAPI;
var
AExtension: string;
AFileType: string;
AListItem: TListItem;
AFileInfo: TSHFileInfo;
begin
// get the extensions file icon
AExtension := ExtractFileExt( FileName );
if SHGetFileInfo( PChar( '*' + AExtension ), FILE_ATTRIBUTE_NORMAL, AFileInfo, SizeOf
( AFileInfo ), SHGFI_SYSICONINDEX or SHGFI_SMALLICON or SHGFI_USEFILEATTRIBUTES ) <> 0 then
AIndex := AFileInfo.iIcon
else
AIndex := -1;
AListItem.ImageIndex := AIndex;
// get extensions file info
if SHGetFileInfo( PChar( '*' + AExtension ), FILE_ATTRIBUTE_NORMAL, Info, SizeOf( Info ),
SHGFI_TYPENAME or SHGFI_USEFILEATTRIBUTES ) then
AFileType := AFileInfo.szTypeName;
end;

Answer 5

Not to sound glib, but Google is your friend. Here are a couple of the first results for "delphi associated icon":
http://www.delphi3000.com/articles/article_453.asp?SK=
http://www.jpgriffiths.com/tutorial/Snippets%5Cgetassociatedicon.html

Answer 6

The other method is to hunt down the extension in the registry under HKEY_CLASSES_ROOT, then follow the key in the default value (if available) and its default is the description. This second level is also where you can get the shell commands to open, or print the file type as well as the path to the default icon.

Answer 7

Here are a couple good examples of using ShGetFileInfo from bitwisemag.com:
http://www.bitwisemag.com/copy/delphi/lpad1.html
http://www.bitwisemag.com/copy/delphi/prog_groups2.html