Adding resources to a program involves using some additional features of Visual C++ Developer Studio. In the case of icons, you use the Image Editor (also called the Graphics Editor) to draw a picture of your icon. This image is stored in an icon file with an extension .ICO. Developer Studio also generates a resource script (that is, a file with the extension .RC, sometimes also called a resource definition file) that lists all the program's resources and a header file (RESOURCE.H) that lets your program reference the resources.

So that you can see how these new files fit together, let's begin by creating a new project, called ICONDEMO. As usual, in Developer Studio you pick New from the File menu, select the Projects tab, and choose Win32 Application. In the Project Name field, type ICONDEMO and click OK. At this point, Developer Studio creates five files that it uses to maintain the workspace and the project. These include the text files ICONDEMO.DSW, ICONDEMO.DSP, and ICONDEMO.MAK (assuming you've selected "Export makefile when saving project file" from the Build tab of the Options dialog box displayed when you select Options from the Tools menu).

Now let's create a C source code file as usual. Select New from the File menu, select the Files tab, and click C++ Source File. In the File Name field, type ICONDEMO.C and click OK. At this point, Developer Studio has created an empty ICONDEMO.C file.

#include <windows.h>
#include "resource.h"

LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    PSTR szCmdLine, int iCmdShow)
{
     TCHAR    szAppName[] = TEXT ("IconDemo") ;
     HWND     hwnd ;
     MSG      msg ;
     WNDCLASS wndclass ;

     wndclass.style         = CS_HREDRAW | CS_VREDRAW ;
     wndclass.lpfnWndProc   = WndProc ;
     wndclass.cbClsExtra    = 0 ;
     wndclass.cbWndExtra    = 0 ;
     wndclass.hInstance     = hInstance ;
     //wndclass.hIcon         = LoadIcon (hInstance, MAKEINTRESOURCE (IDI_ICON)) ;
	 wndclass.hIcon         = LoadIcon(NULL,IDI_APPLICATION);
     wndclass.hCursor       = LoadCursor (NULL, IDC_ARROW) ;
     wndclass.hbrBackground = GetStockObject (WHITE_BRUSH) ;
     wndclass.lpszMenuName  = NULL ;
     wndclass.lpszClassName = szAppName ;
     if (!RegisterClass (&wndclass))
     {
          MessageBox (NULL, TEXT ("This program requires Windows NT!"),
                      szAppName, MB_ICONERROR) ;
          return 0 ;
     }
     
     hwnd = CreateWindow (szAppName, TEXT ("Icon Demo"),
                          WS_OVERLAPPEDWINDOW,
                          CW_USEDEFAULT, CW_USEDEFAULT,
                          CW_USEDEFAULT, CW_USEDEFAULT,
                          NULL, NULL, hInstance, NULL) ;
     
     ShowWindow (hwnd, iCmdShow) ;
     UpdateWindow (hwnd) ;
     
     while (GetMessage (&msg, NULL, 0, 0))
     {
          TranslateMessage (&msg) ;
          DispatchMessage (&msg) ;
     }
     return msg.wParam ;
}

LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
     static HICON hIcon ;
     static int   cxIcon, cyIcon, cxClient, cyClient ;
     HDC          hdc ;
     HINSTANCE    hInstance ;
     PAINTSTRUCT  ps ;
     int          x, y ;
     
     switch (message)
     {
     case WM_CREATE :
          hInstance = ((LPCREATESTRUCT) lParam)->hInstance ;
		  hIcon = LoadIcon (hInstance, MAKEINTRESOURCE (IDI_ICON));
          cxIcon = GetSystemMetrics (SM_CXICON) ;
          cyIcon = GetSystemMetrics (SM_CYICON) ;
          return 0 ;
          
     case WM_SIZE :
          cxClient = LOWORD (lParam) ;
          cyClient = HIWORD (lParam) ;
          return 0 ;

     case WM_PAINT :
          hdc = BeginPaint (hwnd, &ps) ;
          
          for (y = 0 ; y < cyClient ; y += cyIcon)
             for (x = 0 ; x < cxClient ; x += cxIcon)
                    DrawIcon (hdc, x, y, hIcon) ;
               
               EndPaint (hwnd, &ps) ;
               return 0 ;
               
     case WM_DESTROY :
          PostQuitMessage (0) ;
          return 0 ;
     }
     return DefWindowProc (hwnd, message, wParam, lParam) ;
}

If you try compiling this program, you'll get an error because the RESOURCE.H file referenced at the top of the program does not yet exist. However, you do not create this RESOURCE.H file directly. Instead, you let Developer Studio create it for you.

You do this by adding a resource script to the project. Select New from the File menu, select the Files tab, click Resource Script, and type ICONDEMO in the File Name field. Click OK. At this time, Developer Studio creates two new text files: ICONDEMO.RC, the resource script, and RESOURCE.H, a header file that will allow the C source code file and the resource script to refer to the same defined identifiers. Don't try to edit these two files directly; let Developer Studio maintain them for you. If you want to take a look at the resource script and RESOURCE.H without any interference from Developer Studio, try loading them into Notepad. Don't change them there unless you really know what you're doing. Also, keep in mind that Developer Studio will save new versions of these files only when you explicitly direct it to or when it rebuilds the project.

The resource script is a text file. It contains text representations of those resources that can be expressed in text, such as menus and dialog boxes. The resource script also contains references to binary files that contain nontext resources, such as icons and customized mouse cursors.

Now that RESOURCE.H exists, you can try compiling ICONDEMO again. Now you get an error message indicating that IDI_ICON is not defined. This identifier occurs first in the statement

 wndclass.hIcon = LoadIcon (hInstance, MAKEINTRESOURCE (IDI_ICON)) ;

That statement in ICONDEMO has replaced this statement found in previous programs in this book:

 wndclass.hIcon = LoadIcon (NULL, IDI_APPLICATION) ;

It makes sense that we're changing this statement because we've been using a standard icon for our applications and our goal here is to use a customized icon.

So let's create an icon. In the File View window of Developer Studio, you'll see two files listed now—ICONDEMO.C and ICONDEMO.RC. When you click ICONDEMO.C, you can edit the source code. When you click ICONDEMO.RC, you can add resources to that file or edit an existing resource. To add an icon, select Resource from the Insert menu. Click the resource you want to add, which is Icon, and then click the New button.

You are now presented with a blank 32-pixel-by-32-pixel icon that is ready to be colored. You'll see a floating toolbar with a collection of painting tools and a bunch of available colors. Be aware that the color toolbar includes two options that are not exactly colors. These are sometimes referred to as "screen" and "inverse screen." When a pixel is colored with "screen," it is actually transparent. Whatever surface the icon is displayed against will show through. This allows you to create icons that appear to be nonrectangular.

Before you get too far, double-click the area surrounding the icon. You'll get an Icon Properties dialog box that allows you to change the ID of the icon and its filename. Developer Studio will probably have set the ID to IDI_ICON1. Change that to IDI_ICON since that's how ICONDEMO refers to the icon. (The IDI prefix stands for "id for an icon.") Also, change the filename to ICONDEMO.ICO.

The program should now compile and run fine. Developer Studio has put a line in the ICONDEMO.RC resource script that equates the icon file (ICONDEMO.ICO) with an identifier (IDI_ICON). The RESOURCE.H header file contains a definition of the IDI_ICON identifier. (We'll take a look at this in more detail shortly.)

Developer Studio compiles resources by using the resource compiler RC.EXE. The text resource script is converted into a binary form, which is a file with the extension .RES. This compiled resource file is then specified along with .OBJ and .LIB files in the LINK step. This is how the resources are added to the final .EXE file.

When you run ICONDEMO, the program's icon is displayed in the upper left corner of the title bar and in the taskbar. If you add the program to the Start Menu, or if you add a shortcut on your desktop, you'll see the icon there as well.

ICONDEMO also displays the icon in its client area, repeated horizontally and vertically. Using the statement

 hIcon = LoadIcon (hInstance, MAKEINTRESOURCE (IDI_ICON)) ;

the program obtains a handle to the icon. Using the statements

 cxIcon = GetSystemMetrics (SM_CXICON) ; cyIcon = GetSystemMetrics (SM_CYICON) ;

it obtains the size of the icon. The program can then display the icon with multiple calls to

 DrawIcon (hdc, x, y, hIcon) ;

where x and y are the coordinates of where the upper left corner of the displayed icon is positioned.

With most video display adapters in current use, GetSystemMetrics with the SM_ CXICON and SM_CYICON indices will report that the size of an icon is 32 by 32 pixels. This is the size of the icon that we created in the Developer Studio. It is also the size of the icon as it appears on the desktop and the size of the icon displayed in the client area of the ICONDEMO program. It is not, however, the size of the icon displayed in the program's title bar or in the taskbar. That smaller icon size can be obtained from GetSystemMetrics with the SM_CXSMSIZE and SM_CYSMSIZE indices. (The first "SM" means "system metrics"; the embedded "SM" means "small.") For most display adapters in current use, the small icon size is 16 by 16 pixels.

This can be a problem. When Windows reduces a 32-by-32 icon to a 16-by-16 size, it must eliminate every other row and column of pixels. For some complex icon images, this might cause distortions. For this reason, you should probably create special 16-by-16 icons for images where shrinkage is undesirable. Above the icon image in Developer Studio is a combo box labeled Device. To the right of that is a button. Pushing the button invokes a New Icon Image dialog box. Select Small (16x16). Now you can draw another icon.

Now that we've mastered the practical stuff, let's take a closer look at what's going on under the hood.