Pascal Newsletter #4
The full source code examples of this issue are available for download.
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Pascal Newsletter #4 INDEX 1. A FEW WORDS FROM THE EDITOR 2. GETTING THE ICON OF AN APPLICATION OR DOCUMENT ExtractAssociatedIcon FIND FILE: Adding icons 3. ERRATA 4. DETERMINING IF THERE IS AN ACTIVE CONNECTION TO THE INTERNET 5. DELPHI TUTORIALS ________________________________________________________________________ 1. A FEW WORDS FROM THE EDITOR I'm happy to announce that soon we will have our own domain name and hopefully we will be moved to our new site by next week. We are going commercial, and this means in the future there will be ads in the web pages to help pay the bills and eventually we will have to include a little ad in this newsletter, but we will try to keep it ad-free for as long as we can. Regards, Ernesto De Spirito eds2004 @ latiumsoftware.com ________________________________________________________________________ JfControls Library. Multi-language. Multi-appearance. Skins. Privileges. More than 40 integrated and customizable components. Impressive GUI. Centralized resources administration. Multiple programming problems solved. For Delphi 3-7 and C++ Builder 3-6. http://www.jfactivesoft.com/ ________________________________________________________________________ 2. GETTING THE ICON OF AN APPLICATION OR DOCUMENT ExtractAssociatedIcon ===================== To get the icon of an application or document we can use this API function declared in the ShellAPI unit: function ExtractAssociatedIcon(hInst: HINST; lpIconPath: PChar; var lpiIcon: Word): HICON; stdcall; hInst: The application handle. This value is contained in the predefined variable HInstance. lpIconPath: A pointer to a character buffer that should contain a null terminated string with the full path name of the application, library (DLL) or document. If it is a document, the function will place there the full pathname of the associated application from where the icon was extracted, so we should allocate a buffer large enough. lpiIcon: The icon index (the first icon in the file has an index of 0). If lpIconPath specifies a document, then lpiIcon is set by the function (that's why it is passed by reference) to the index position of the actual icon taken from the associated executable (defined in the file association). Return value: If the function fails, it returns 0. If it succeeds, it returns an icon handle, which is an integer value Windows uses to identify the allocated resource. It is not necessary to call the API DestroyIcon to release the icon since it'll be deallocated automatically when the application finishes, although you can do it if you want. Now, what do we do with the icon handle? Normally what we want is an icon, namely and instance of the TIcon class. All we have to do is create a TIcon object and assign this handle to its Handle property. If later we assign the Handle property to another value, the previous icon will be automatically be released. The same happens if the TIcon object is freed. FIND FILE: Adding icons ======================= Continuing the work with the Find File application we use to show some programming tips, this time we will add the file icons in the ListView control. The first thing we'll do is placing an ImageList on the form (normally it's located in the Win32 palette) and then we'll assign it to the SmallImages property of ListView1. Now it's time to add code in the AddFileName method of TThread1. We need four more variables: Icon: TIcon; IconIndex: word; Buffer: array[0..2048] of char; IconHandle: HIcon; And then we add the following code (for example right after the line "ListItem.Caption := FileName;"): StrCopy(@Buffer, PChar(Location + FileName)); IconIndex := 0; IconHandle := ExtractAssociatedIcon(HInstance, Buffer, IconIndex); if IconHandle <> 0 then begin Icon := TIcon.Create; Icon.Handle := IconHandle; ListItem.ImageIndex := OwnerForm.ImageList1.AddIcon(Icon); Icon.Free; end; Finally we empty the ImageList right after we empty the ListView in the Initialize method of TThread1, so it doesn't grow "indefinitely": OwnerForm.ImageList1.Clear; Now you can try the example to see it working. As usual, the full source code is available in our web site: http://www.latiumsoftware.com/download/p0004.zip ________________________________________________________________________ 3. ERRATA In the last issue we showed how to take coordinates relative to a control and make them relative to the screen adding to them the form's position and the control's position in the form. This doesn't account correctly for the borders and title bar of the form, and if the control was inside another container we would have to add its coordinates too... The easy way is using the property ClientOrigin that all descendants of TControl have and forget about all this. For instance, in our ListView1MouseDown procedure, instead of PopupMenu1.Popup( Left + ListView1.Left + X + 5, Top + ListView1.Top + Y + 20); we should use PopupMenu1.Popup( ListView1.ClientOrigin.X + X, ListView1.ClientOrigin.Y + Y); ________________________________________________________________________ 4. DETERMINING IF THERE IS AN ACTIVE CONNECTION TO THE INTERNET It is easy to know if you are connected to the net. Basically all you have to do is checking the first byte of the data under the following Windows Registry key value: + HKEY_LOCAL_MACHINE + System + CurrentControlSet + Services + RemoteAccess --> Remote Connection This data element consists of four bytes, so we use ReadBinaryData instead of the ReadString method we used when we gave an introduction to the Windows Registry in the second issue of the former Delphi Newsletter. If the first of these bytes equals 1, you are connected to the net, otherwise not (it should then be 0). The following function returns True if you are connected to the net: uses Registry, WinSock; function InternetConnection: boolean; var Reg: TRegistry; RemoteConnection: array [0..3] of byte; Error: boolean; HostName: array[0..63] of char; WSData: TWSAData; begin Result := False; Error := False; Reg := nil; try Reg := TRegistry.Create(KEY_QUERY_VALUE); Reg.RootKey := HKEY_LOCAL_MACHINE; if Reg.OpenKeyReadOnly('\System\CurrentControlSet\Services\' + 'RemoteAccess') then begin try Reg.ReadBinaryData('Remote Connection', RemoteConnection, SizeOf(RemoteConnection)); if RemoteConnection[0] = 1 then Result := True; except Error := True; end; Reg.CloseKey; end; except Error := True; end; Reg.Free; if Error then // Try another way of finding if there is a connection if WSAStartup($200, WSData) = 0 then begin GetHostName(HostName, SizeOf(HostName)); if GetHostByName(HostName) <> nil then Result := True; WSACleanup; end; end; If an error occurs while accessing the Registry, the function tries an alternative method of detecting an internet connection using the WinSock APIs. WSAStartup initiates the Windows Sockets service and in this case we request up to version 2.0 if possible. WSData is a record where this function will put some information about the Windows Sockets DLL. If WSAStartup returns 0 (meaning it succeeded) we call GetHostName to get the name of our computer, that we use it to call GetHostByName, that in turn returns a pointer to a record with information about the host address/es, or Nil if there is no connection, so we use this value to determine whether there is a connection. Once we are done with the Windows Sockets we should close the session by calling WSACleanup. ________________________________________________________________________ 5. DELPHI TUTORIALS One of the things we are most asked is information about tutorials on Delphi programming, so here are a few links: * Astentech Delphi Tutorial List http://www.astentech.com/tutorials/Delphi.html * Delphi Tutorial http://privat.schlund.de/b/bossung/delphi/tutorial_multipage.html * The Software Developers Pages http://home.planet.nl/~beenh012/sdp/ * Delphi and Pascal programming tutorials http://ourworld.compuserve.com/homepages/TK_Boyd/Tut.htm * DelphiLand: programming courses, tips, sources, utilities http://www.festra.com/ * Frank's Delphi Lessons http://www.svn.net/ffortino/ ________________________________________________________________________ YOU CAN HELP US We need your help to keep this newsletter going and growing. You can help by referring the newsletter to your colleagues: http://www.latiumsoftware.com/en/pascal/delphi-newsletter.php Or you can help by voting for us in some or all of these rankings to give more visibility to our web site and thus increase the number of subscriptions to this newsletter: http://www.sandbrooksoftware.com/cgi-bin/TopSite2/rankem.cgi?id=latium http://news.optimax.com/delphi/links/links.exe/click?id=70C517ECAE6E http://www.programmingpages.com/?r=latiumsoftwarecomenpascal http://www.top219.org/cgi-bin/vote.cgi?delphi&83 http://top100borland.com/in.php?who=20 http://top200.jazarsoft.com/delphi/rank.php3?id=latium http://213.65.224.200/cgi-bin/toplist.cgi/hits?Id=80 It's just a few seconds for you that REALLY mean a lot to us. ________________________________________________________________________ If you haven't received the full source code examples for this issue, you can get them from http://www.latiumsoftware.com/download/p0004.zip ________________________________________________________________________ This newsletter is provided "AS IS" without warranty of any kind. Its use implies the acceptance of our licensing terms and disclaimer of warranty you can read at http://www.latiumsoftware.com/en/legal.php where you will also find a note about legal trademarks. Articles are copyright of their respective authors and they are reproduced here with their permission. You can redistribute this newsletter as long as you do it in full (including copyright notices), without changes, and gratis. ________________________________________________________________________ Main page: http://www.latiumsoftware.com/en/pascal/delphi-newsletter.php Group home page: http://groups.yahoo.com/group/pascal-newsletter/ Subscribe/join: pascal-newsletter-subscribe@yahoogroups.com Unsubscribe/leave: pascal-newsletter-unsubscribe@yahoogroups.com Problems with your subscription? eds2004 @ latiumsoftware.com ________________________________________________________________________ Latium Software http://www.latiumsoftware.com/en/index.php Copyright (c) 2000 by Ernesto De Spirito. 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