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API - Application Programmer's Interface

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Submitted on: 1/22/2015 6:01:00 PM
By: Abdulaziz Alfoudari (from psc cd)  
Level: Advanced
User Rating: By 26 Users
Compatibility: VB 5.0, VB 6.0
Views: 509
 
     Visit us at: http://www.vbparadise.com. As a programmer you might never have to use a Windows API.... Nahhh! The fact is that serious programmers use API all the time. When they need to do something that VB cannot handle, they turn to the Windows API! The API are procedures that exist in files on your PC which you can call from within your VB program - and there are thousands of them!. Written by Microsoft, debugged by tens of thousands of users, and available for free with Windows - the API are one of the very best tools you have available to add power to your VB application.

 
				

Visit Us At: http://www.vbparadise.com

API - Application Programmer's Interface

When Microsoft wrote Windows they put a huge amount of code into procedure libraries which programmers can access. No matter which language you're using (VB, C++, ...) you can use the Windows API to greatly expand the power of your application.

There are a lot of Windows programs whose code is spread across multiple files. The .EXE file does not always contain all of the code that a programmer might use. For example, by creating his own library of procedures (usually in the form of a file with a .DLL extension) a programmer can allow more than one of his applications to access the same code.

Microsoft does a similar thing with Windows. There are many files which have code that you can access, but the three most often named files are:

  • user32.dll - controls the visible objects that you see on the screen
  • gdi32 - home of most graphics oriented API
  • kernel32.dll - provides access to low level operating system features

Later, I'll bring up some of the other files whose procedures you might want access. However, there are some key issues which you should note before making a decision to use an API call.

  • Version Compatibility
    Microsoft has long been known to update it's files without much fanfare - read that as without telling anyone about it until it's already happened! And often, the updated code may not perform exactly as did the older version. Users often find this out by seeing unexected errors or by having their system crash and/or lock up on them! In VB5 there were a huge number of programmer's who got bit by this problem.

    If you stick with the basic 3 OS files listed above, you won't see to much of this. But the further away you go from the main 3 files, the more likely you are to get into code which hasn't seen the testing and improvement cycle that the main Windows OS files have gone through.

  • File Size
    One of the very major downsides to the concept of API is that all of this great code lives in some very big files! Worse yet, sometimes the API you want are spread over multiple files and you may be using only one or two procedures from enormous files which have hundreds of procedures in them. Where this becomes a problem is in a)load time - where it can takes several seconds to load the procedure libraries, and b) - where you want to distribute your application and in order to make sure that all of the procedure libraries are on your user's machine, you have to put all of them into the distribute files. This can add many megabytes of files to your distribution applications. It is a major problem for distribution of software over the net, where 5 minutes per megabyte can deter a usage from trying out an application just because he doesn't want to wait for the download!
  • Documentation
    Finding the documentation of what procedures are in a library and how to use them can be very difficult. On my PC I have 3,380 files with a .DLL extension with a total size of 539MB. That's a lot of code! Unfortunately I can count on one hand the pages of documentation that I have to tell me what that code is or does! You'll learn how to use DLLs in this tutorial, but without the documentation from the creator of the DLLs you cannot use them successfully.

Despite these problems, the powerful magic of the API is that they are code which you don't have to write. If you've read my Beginner's section you know that I am a big fan of using 3rd party software to lighten my own programming load. As with 3rd party controls, the API provide procedures which someone else wrote, debugged, and made availble for you to benefit from. In the Windows DLLs files, there are literally thousands of procedures. The key to API programming is learning which of these procedures are useful and which ones you are unlikely to ever need! This tutorial tries to address just that problem.

Getting Started It's actually simpler than you might imagine. By now, you've already written procedures for your own VB programs. Using procedures from other files is almost exactly the same as using procedures from within your own program.

The one big difference is that you must tell your application which file the procedure is contained in. To do so, you must put 1 line of code into your VB program. And, you have to do this for every external procedure that you plan to use. I suppose it would be nice for VB to have the ability to find the procedures for you - but you can see that searching through the 3,380 procedures on my PC might slow my applications down a lot!

Ok, let's get to an example. Telling VB about the procedure you want to use is known as "declaring" the procedure, and (no surprise) it uses a statement which starts with the word declare. Here's what a declaration looks like:

Declare Function ExitWindowsEx Lib "user32" (ByVal uFlags as Long, ByVal dwReserved as Long) as Long

Let's take about the parts of the declaration statement:

  • "Declare"
    This is reserved word that VB uses to begin a declaration. There is no alternative - you have to use it.
  • "Function"
    Also a reserved word, but in this case it distinguishes between a SUB procedured and a FUNCTION procedure. The API use Function procedures so that they can return a value to indicate the results of the action. Although you can discard the returned value, it's also possible to check the return value to determine that the action was successfully completed. completed. alternative - you have to use it.
  • "ExitWindowsEx"
    Inside each DLL is a list of the procedures that it contains. Normally, in a VB declaration statement you simply type in the name of the procedure just as it is named in the DLL. Sometimes, the DLL true name of the procedure may be a name that is illegal in VB. For those cases, VB allows you to put in the text string "Alias NewProcedurename" right behind the filename. In this example, VB would make a call to the procedure by using the name "NewProcedureName".
  • "Lib 'user32'"
    Here's where you tell VB which file the procedure is in. Normally you would put "user32.dll", showing the extension of the procedure library. For the special case of the three Windows system DLLs listed above, the API will recognize the files when simply named "user32", "kernel32", and "gdi32" - without the DLL extensions shown. In most other cases you must give the complete file name. Unless the file is in the system PATH, you must also give the complete path to the file.
  • "(ByVal uFlags as Long ...)"
    Exactly like your own procedures, Windows API functions can have a list of arguments. However, while your VB procedures often use arguments passed by reference (i.e., their values can be changed), most Windows API require that the arguments be passed by value (i.e, a copy of the argument is passed to the DLL and the originial variable cannot be changed).

    Also, you'll note that a constant or variable is normally used as the argument for an API call. It's technically acceptable to simply use a number for an argument but it is common practice among experienced programmers to create constants (or variables) whose name is easy to remember and then to use those in the argument list. When you're reading or debugging your code later, the use of these easy to read constant/variable names makes it much easier to figure out what went wrong!

  • "as Long"
    This is exactly like the code you use to create your own functions. Windows API are functions which return values and you must define what type of variable is returned.

While I make it sound simple (and it is), there are still issues which ought to concern you when using the Windows API. Because the API code executes outside the VB program itself, your own program is susceptable to error in the external procedure. If the external procedure crashes, then your own program will crash as well. It is very common for an API problem to freeze your system and force a reboot.

The biggest issue that VB programmers would see in this case is that any unsaved code will be lost!. So remember the rule when using API - save often!

Because many of the DLLs you will use have been debugged extensively you probably won't see many cases where the DLL crashes because of programming bug. Far more frequently VB programmers will see a crash because they passed arguments to the procedure which the procedure could not handle! For example, passing a string when an integer was needed will likely crash the system. The DLLs don't include extensive protection in order to keep their own code size small and fast.

It is simple to say that if you pass the correct type of argument, that you won't see API crashes. However, the documentation is not always clear exactly what argument type is needed, plus when writing code it is all too common to simply make a mistake!

Finally, it is the case that most of the DLLs you'll want to use were written in C++. The significance of this is that the data types in C++ do not map cleanly into the data types that are used in Visual Basic. Here are some of the issues which you need to be aware of:

  • Issue1
  • Issue2

Okay, stay with me just a bit longer and we'll get into the actual use of some API. But first, here is a list of other DLLs which have procedures that could be of use to you. These DLLs will show up later in this tutorial when we get to the API which I recommend that you consider for use in your own applications.

  • Advapi32.dll - Advanced API services including many security and Registry calls
  • Comdlg32.dll - Common dialog API library
  • Lz32.dll - 32-bit compression routines
  • Mpr.dll - Multiple Provider Router library
  • Netapi32.dll - 32-bit Network API library
  • Shell32.dll - 32-bit Shell API library
  • Version.dll - Version library
  • Winmm.dll - Windows multimedia library
  • Winspool.drv - Print spoolder interface

Often, the documentation that you might find for an API will be written for a C++ programmer. Here's a short table which helps you translate the C++ variable type declaration to its equivalent in Visual Basic:

ATOM ByVal variable as Integer
BOOL ByVal variable as Long
BYTE ByVal variable as Byte
CHAR ByVal variable as Byte
COLORREF ByVal variable as Long
DWORD ByVal variable as Long
HWND ByVal variable as Long
HDC ByVal variable as Long
HMENU ByVal variable as Long
INT ByVal variable as Long
UINT ByVal variable as Long
LONG ByVal variable as Long
LPARAM ByVal variable as Long
LPDWORD variable as Long
LPINT variable as Long
LPUINT variable as Long
LPRECT variable as Type any variable of that User Type
LPSTR ByVal variable as String
LPCSTR ByVal variable as String
LPVOID variable As Any use ByVal when passing a string
LPWORD variable as Integer
LPRESULT ByVal variable as Long
NULL ByVal Nothing or ByVal 0& or vbNullString
SHORT ByVal variable as Integer
VOID Sub Procecure not applicable
WORD ByVal variable as Integer
WPARAM ByVal variable as Long

We're not quite ready to get into using the API. Here is a scattering of issues/comments about using API which you will want to be aware of:

  • Declare
    • DECLARE in standard module are PUBLIC by default and be used anywhere in your app
    • DECLARE in any other module are PRIVATE to that module and MUST BE marked PRIVATE
    • Procedure names are CASE-SENSITIVE
    • You cannot Declare a 16-bit API function in VB6
  • ALIAS
    • Is the "real" name of the procedure as found in the DLL
    • If the API uses string, you MUST use ALIAS with "A" to specify the correct character set (A=ANSI W=UNICODE)
    • WinNT supports W, but Win95/Win98 do not
    • Some DLLs have illegal VB name, so you must use ALIAS to rename the procedure
    • Can also be the ordinal number of the procedure
  • Variable Type
    • Very few DLLs recognize VARIANT
    • ByRef is VB default
    • Most DLLs expect ByVal
    • In C documentation, C passes all arguments except arrays by value
    • AS ANY can be used but it turns off all type checking
  • Strings
    • API generally require fixed length strings
    • Pass string ByVal means passing pointer to first data byte in the string
    • Pass string ByRef means passing memory address to another memory addresss which refers to first data byte in the string
    • Most DLLs expect LPSTR (ASCIIZ) strings (end in a null character), which point to the first data byte
    • VB Strings should be passed ByVal (in general)
    • VB uses BSTR strings (header + data bytes) - BSTR is passed as a pointer to the header
    • DLL can modify data in a string variable that it receives as an argument - WARNING: if returned value is longer than passed value, system error occurs!
    • Generally, API do not expect string buffers longer than 255 characters
    • C & VB both treat a string array as an array of pointers to string data
    • Most API require you to pass the length of the string and to fill the string wih spaces
  • Arrays
    • Pass entire array by passing the first element of the array ByRef
    • Pass individual elements of array just like any other variable
    • If pass pass binary data to DLL, use array of Byte characters
  • Callback Function
    • Use AddressOf to pass a user-defined function that the DLL procedure can use
    • Must have specific set of arguments, AS DEFINED by the API procedure
    • Procedure MUST be in a .BAS module
    • Passed procedure must be As Any or As Long
  • Passing a null value
    • To pass a null value - zero-length string ("") will not work
    • To pass a null value - use vbNullString
    • To pass a null value - change Type to Long and then use 0&
  • Window Handle
    • A handle is simply a number assigned by Windows to each window
    • In VB, the handle is the same as the property hWnd
    • Handles are always Long variable types
  • Callbacks
    • Some API can run one of you own VB functions. Your VB function is called a "Callback"
    • VB supports callbacks with a function "AddressOf", which give the API the location of the function to execute
    • Callback functions must be in a module. They cannot be in a form.
  • Subclassing
    • All windows work by processing messages from the Windows operating system
    • You can change how a window responds to a message by intercepting the message
    • To intercept a message, use the API SetWindowsLong
  • Miscellaneous
    • Control properties MUST be passed by value (use intermediate value to pass ByRef)
    • Handles - always declare as ByVal Long
    • Variant - to pass Variant to argument that is not a Variant type, pass the Variant data ByVal
    • UDT - cannot be passed except as ByRef

Which API Should I Use?
Finally we get to the good part. First the bad news, then the good news. In this section I do not provide code that you can simply copy into your own applications. The good news is that I provide a list of features that you might want to incorporate into your own application and then tell you which of the API to use. For the purposes of this relatively short tutorial, the best I can do is to point you off in the right direction!

In case you don't know, VB6 comes with a tool to help you use API in your own applications. The API Viewer is installed automatically with VB, and to use it go to the Start/Programs/VB/Tools menu and select "API Viewer". The viewer actions much like my own VB Information Center Code Librarian in that you can browse through the various API, select one for copying to the clipboard, and then paste the declaration into your own application's code window. You'll definitely want to try this out. The data file that comes with the viewer if very extensive, listing 1550 API Declarations.

In my case I use API regularly, but I've never come close to using 1550 API. At best, I barely have broken the 100 mark. It seems that for the most part I can get VB to do whatever task I want without resorting to the API. However, in some cases you just can do any better than a few lines of API code to get the job done! So, here's my own list of useful tasks and the API needed to perform them:

 

Play sound Declare Function sndPlaySound Lib "winmm.dll" Alias "sndPlaySoundA" (ByVal lpszSoundName as string, ByVal uFlags as Long) as Long
Result = sndPlaySound (SoundFile, 1)
 
SubClassing Declare Function CallWindowProc Lib "user32" Alias "CallWindowProcA" (ByVal lpPrevWndFunc as Long, ByVal hwnd as Long, byval msg as long, byval wParam as long, byval lParam as Long ) as long
Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
 
Run associated EXE Declare Function ShellExecute Lib "shell32.dll" Alias "ShellExecuteA" (ByVal hwnd As Long, ByVal lpOperation As String, ByVal lpFile As String, ByVal lpParameters As String, ByVal lpDirectory As String, ByVal nShowCmd As Long) As Long
 
List window handles Declare Function EnumWindows Lib "user32" (ByVal lpEnumFunc As Long, ByVal lParam As Long) As Long
 
Find prior instance of EXE Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
 
Draw dotted rectangle Declare Function DrawFocusRect Lib "user32" Alias "DrawFocusRect" (ByVal hdc As Long, lpRect As RECT) As Long
 
Invert colors of rectangle Declare Function InvertRect Lib "user32" Alias "InvertRect" (ByVal hdc As Long, lpRect As RECT) As Long
 
Get cursor position Declare Function GetCursorPos Lib "user32" Alias "GetCursorPos" (lpPoint As POINTAPI) As Long
 
Always on top Declare Function SetWindowPos Lib "user32" Alias "SetWindowPos" (ByVal hwnd As Long, ByVal hWndInsertAfter As Long, ByVal x As Long, ByVal y As Long, ByVal cx As Long, ByVal cy As Long, ByVal wFlags As Long) As Long
 
Send messages to a window Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long
 
Find directories Declare Function GetWindowsDirectory Lib "kernel32" Alias "GetWindowsDirectoryA" (ByVal lpBuffer As String, ByVal nSize As Long) As Long
Declare Function GetSystemDirectory Lib "kernel32" Alias "GetSystemDirectoryA" (ByVal lpBuffer As String, ByVal nSize As Long) As Long
Declare Function GetTempPath Lib "kernel32" Alias "GetTempPathA" (ByVal nBufferLength As Long, ByVal lpBuffer As String) As Long
Declare Function GetCurrentDirectory Lib "kernel32" Alias "GetCurrentDirectory" (ByVal nBufferLength As Long, ByVal lpBuffer As String) As Long
 
Text alignment Declare Function GetTextAlign Lib "gdi32" Alias "GetTextAlign" (ByVal hdc As Long) As Long
Declare Function SetTextAlign Lib "gdi32" Alias "SetTextAlign" (ByVal hdc As Long, ByVal wFlags As Long) As Long
 
Flash a title bar Declare Function FlashWindow Lib "user32" Alias "FlashWindow" (ByVal hwnd As Long, ByVal bInvert As Long) As Long
 
Manipulate bitmaps Declare Function BitBlt Lib "gdi32" Alias "BitBlt" (ByVal hDestDC As Long, ByVal x As Long, ByVal y As Long, ByVal nWidth As Long, ByVal nHeight As Long, ByVal hSrcDC As Long, ByVal xSrc As Long, ByVal ySrc As Long, ByVal dwRop As Long) As Long
Declare Function PatBlt Lib "gdi32" Alias "PatBlt" (ByVal hdc As Long, ByVal x As Long, ByVal y As Long, ByVal nWidth As Long, ByVal nHeight As Long, ByVal dwRop As Long) As Long
Declare Function StretchBlt Lib "gdi32" Alias "StretchBlt" (ByVal hdc As Long, ByVal x As Long, ByVal y As Long, ByVal nWidth As Long, ByVal nHeight As Long, ByVal hSrcDC As Long, ByVal xSrc As Long, ByVal ySrc As Long, ByVal nSrcWidth As Long, ByVal nSrcHeight As Long, ByVal dwRop As Long) As Long
Declare Function CreateCompatibleBitmap Lib "gdi32" Alias "CreateCompatibleBitmap" (ByVal hdc As Long, ByVal nWidth As Long, ByVal nHeight As Long) As Long
Declare Function CreateCompatibleDC Lib "gdi32" Alias "CreateCompatibleDC" (ByVal hdc As Long) As Long
 
Rotate text Declare Function CreateFontIndirect Lib "gdi32" Alias "CreateFontIndirectA" (lpLogFont As LOGFONT) As Long
 
Timing Declare Function GetTickCount Lib "kernel32" Alias "GetTickCount" () As Long
 
File information Declare Function GetFileAttributes Lib "kernel32" Alias "GetFileAttributesA" (ByVal lpFileName As String) As Long
Declare Function GetFileSize Lib "kernel32" Alias "GetFileSize" (ByVal hFile As Long, lpFileSizeHigh As Long) As Long
Declare Function GetFullPathName Lib "kernel32" Alias "GetFullPathNameA" (ByVal lpFileName As String, ByVal nBufferLength As Long, ByVal lpBuffer As String, ByVal lpFilePart As String) As Long
 
Get window information Declare Function GetClassName Lib "user32" Alias "GetClassNameA" (ByVal hwnd As Long, ByVal lpClassName As String, ByVal nMaxCount As Long) As Long
Declare Function GetWindowText Lib "user32" Alias "GetWindowTextA" (ByVal hwnd As Long, ByVal lpString As String, ByVal cch As Long) As Long
Declare Function GetParent Lib "user32" Alias "GetParent" (ByVal hwnd As Long) As Long
 
Identify window at cursor Declare Function WindowFromPoint Lib "user32" Alias "WindowFromPoint" (ByVal xPoint As Long, ByVal yPoint As Long) As Long
 
Registry editing Declare Function RegCreateKey Lib "advapi32.dll" Alias "RegCreateKeyA" (ByVal hKey As Long, ByVal lpSubKey As String, phkResult As Long) As Long
Declare Function RegDeleteKey Lib "advapi32.dll" Alias "RegDeleteKeyA" (ByVal hKey As Long, ByVal lpSubKey As String) As Long
Declare Function RegDeleteValue Lib "advapi32.dll" Alias "RegDeleteValueA" (ByVal hKey As Long, ByVal lpValueName As String) As Long
Declare Function RegQueryValueEx Lib "advapi32.dll" Alias "RegQueryValueExA" (ByVal hKey As Long, ByVal lpValueName As String, ByVal lpReserved As Long, lpType As Long, lpData As Any, lpcbData As Long) As Long
Declare Function RegSetValueEx Lib "advapi32.dll" Alias "RegSetValueExA" (ByVal hKey As Long, ByVal lpValueName As String, ByVal Reserved As Long, ByVal dwType As Long, lpData As Any, ByVal cbData As Long) As Long
 
Drawing functions Declare Function MoveToEx Lib "gdi32" Alias "MoveToEx" (ByVal hdc As Long, ByVal x As Long, ByVal y As Long, lpPoint As POINTAPI) As Long
Declare Function LineTo Lib "gdi32" Alias "LineTo" (ByVal hdc As Long, ByVal x As Long, ByVal y As Long) As Long
Declare Function Ellipse Lib "gdi32" Alias "Ellipse" (ByVal hdc As Long, ByVal X1 As Long, ByVal Y1 As Long, ByVal X2 As Long, ByVal Y2 As Long) As Long
 
Get icon Declare Function ExtractIcon Lib "shell32.dll" Alias "ExtractIconA" (ByVal hInst As Long, ByVal lpszExeFileName As String, ByVal nIconIndex As Long) As Long
 
Screen capture Declare Function SetCapture Lib "user32" Alias "SetCapture" (ByVal hwnd As Long) As Long
Declare Function CreateDC Lib "gdi32" Alias "CreateDCA" (ByVal lpDriverName As String, ByVal lpDeviceName As String, ByVal lpOutput As String, lpInitData As DEVMODE) As Long
Declare Function DeleteDC Lib "gdi32" Alias "DeleteDC" (ByVal hdc As Long) As Long
Declare Function BitBlt Lib "gdi32" Alias "BitBlt" (ByVal hDestDC As Long, ByVal x As Long, ByVal y As Long, ByVal nWidth As Long, ByVal nHeight As Long, ByVal hSrcDC As Long, ByVal xSrc As Long, ByVal ySrc As Long, ByVal dwRop As Long) As Long
Declare Function ReleaseCapture Lib "user32" Alias "ReleaseCapture" () As Long
Declare Function ClientToScreen Lib "user32" Alias "ClientToScreen" (ByVal hwnd As Long, lpPoint As POINTAPI) As Long
 
Get user name Declare Function GetUserName Lib "advapi32.dll" Alias "GetUserNameA" (ByVal lpBuffer As String, nSize As Long) As LongDeclare Function GetUserName Lib "advapi32.dll" Alias "GetUserNameA" (ByVal lpBuffer As String, nSize As Long) As Long
 
Get computer name Declare Function GetComputerName Lib "kernel32" Alias "GetComputerNameA" (ByVal lpBuffer As String, nSize As Long) As LongDeclare Function GetComputerName Lib "kernel32" Alias "GetComputerNameA" (ByVal lpBuffer As String, nSize As Long) As Long
 
Get volume name/serial# Declare Function GetVolumeInformation Lib "kernel32" Alias "GetVolumeInformationA" (ByVal lpRootPathName As String, ByVal lpVolumeNameBuffer As String, ByVal nVolumeNameSize As Long, lpVolumeSerialNumber As Long, lpMaximumComponentLength As Long, lpFileSystemFlags As Long, ByVal lpFileSystemNameBuffer As String, ByVal nFileSystemNameSize As Long) As Long
 
Identify drive type Declare Function GetDriveType Lib "kernel32" Alias "GetDriveTypeA" (ByVal nDrive As String) As Long
 
Get free space Declare Function GetDiskFreeSpace Lib "kernel32" Alias "GetDiskFreeSpaceA" (ByVal lpRootPathName As String, lpSectorsPerCluster As Long, lpBytesPerSector As Long, lpNumberOfFreeClusters As Long, lpTotalNumberOfClusters As Long) As Long
 
INI editing Declare Function WritePrivateProfileSection Lib "kernel32" Alias "WritePrivateProfileSectionA" (ByVal lpAppName As String, ByVal lpString As String, ByVal lpFileName As String) As Long
Declare Function WritePrivateProfileString Lib "kernel32" Alias "WritePrivateProfileStringA" (ByVal lpApplicationName As String, ByVal lpKeyName As Any, ByVal lpString As Any, ByVal lpFileName As String) As Long
Declare Function GetPrivateProfileInt Lib "kernel32" Alias "GetPrivateProfileIntA" (ByVal lpApplicationName As String, ByVal lpKeyName As String, ByVal nDefault As Long, ByVal lpFileName As String) As Long
Declare Function GetPrivateProfileSection Lib "kernel32" Alias "GetPrivateProfileSectionA" (ByVal lpAppName As String, ByVal lpReturnedString As String, ByVal nSize As Long, ByVal lpFileName As String) As Long
Declare Function GetPrivateProfileString Lib "kernel32" Alias "GetPrivateProfileStringA" (ByVal lpApplicationName As String, ByVal lpKeyName As Any, ByVal lpDefault As String, ByVal lpReturnedString As String, ByVal nSize As Long, ByVal lpFileName As String) As Long
 
Put icon in system tray Declare Function CallWindowProc Lib "user32" Alias "CallWindowProcA" (ByVal lpPrevWndFunc As Long, ByVal hWnd As Long, ByVal Msg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long) As Long
Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Declare Function Shell_NotifyIcon Lib "shell32.dll" Alias " Shell_NotifyIconA" (ByVal dwMessage As Long, lpData As NOTIFYICONDATA) As Long
Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (Destination As Any, Source As Any, ByVal Length As Long)
Declare Function DrawEdge Lib "user32" Alias "DrawEdge" (ByVal hdc As Long, qrc As RECT, ByVal edge As Long, ByVal grfFlags As Long) As Long
 
Wait for program to stop Declare Function CreateProcess Lib "kernel32" Alias "CreateProcessA" (ByVal lpApplicationName As String, ByVal lpCommandLine As String, lpProcessAttributes As SECURITY_ATTRIBUTES, lpThreadAttributes As SECURITY_ATTRIBUTES, ByVal bInheritHandles As Long, ByVal dwCreationFlags As Long, lpEnvironment As Any, ByVal lpCurrentDriectory As String, lpStartupInfo As STARTUPINFO, lpProcessInformation As PROCESS_INFORMATION) As Long
Declare Function WaitForSingleObject Lib "kernel32" Alias "WaitForSingleObject" (ByVal hHandle As Long, ByVal dwMilliseconds As Long) As Long
 
Stop ctrl-alt-del Declare Function SystemParametersInfo Lib "user32" Alias "SystemParametersInfoA" (ByVal uAction As Long, ByVal uParam As Long, ByRef lpvParam As Any, ByVal fuWinIni As Long) As Long

Hopefully, this section of the tutorial has sparked some excitement! You should now see that a door of tremendous proportions has been opened to you. You've begun to leave the limitations of VB behind and joined the rest of the programming community who have already been using the API for years. I hope to add quite a bit to this tutorial section so check back often over the next few weeks.


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