DOCUMENT:Q29733 17-JUN-1999 [win16sdk] TITLE :HOWTO: Drawing a Different Icon for Each Application Instance PRODUCT :Microsoft Windows Software Development Kit PROD/VER:WINDOWS:3.1 OPER/SYS: KEYWORDS:kb16bitonly kbSDKWin16 ====================================================================== 3.00 3.10 WINDOWS kbprg ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Windows Software Development Kit (SDK) 3.1 ------------------------------------------------------------------------------- SUMMARY ======= An application can use the DrawIcon function in its paint procedure to display a different icon for each application instance. The method has the following five steps. MORE INFORMATION ================ 1. In the WNDCLASS data structure used to register the application's main window class, set the hIcon field to NULL. This prevents Windows from drawing an icon when the application is minimized. The following code demonstrates this step: int index; // global variable to count application instances // This function initializes the first application instance void InitFirst(HANDLE hInstance) { WNDCLASS rClass; // window class structure rClass.lpszClassName = "HELLO"; rClass.hInstance = hInstance; rClass.lpfnWndProc = WindowProc; rClass.hCursor = LoadCursor(NULL, IDC_ARROW); // If hIcon is NULL, Windows will not draw icon. Application // paints its own icon as appropriate. rClass.hIcon = NULL; rClass.lpszMenuName = NULL; rClass.hbrBackground = COLOR_WINDOW + 1; rClass.style = CS_HREDRAW | CS_VREDRAW; rClass.cbClsExtra = 0; rClass.cbWndExtra = 0; RegisterClass(&rClass); // register the class index = 1; // set counter to indicate first instance } 2. The GetInstanceData function provides the value of the instance counter from the previous instance. Adding one to this value provides the value for the current instance, as follows: void InitNext(HANDLE hInstance, HANDLE hPrevInstance) { GetInstanceData(hPrevInstance, (PSTR)&index, sizeof(int)); index++; } 3. During the instance initialization function, load the icon for the current instance from the application's resources. In this case, Icon1, Icon2, Icon3, and Icon4 are individual icons declared in the application's resources. The following code demonstrates this procedure: HICON hIcon; // icon handle for this instance void InitEvery(HANDLE hInstance, int cmdShow) { HWND hWnd; hInst = hInstance; // store instance in global variable for // window procedures to use switch (index) { case 1: hIcon = LoadIcon(hInstance, "Icon1"); break; case 2: hIcon = LoadIcon(hInstance, "Icon2"); break; case 3: hIcon = LoadIcon(hInstance, "Icon3"); break; default: hIcon = LoadIcon(hInstance, "Icon4"); } CreateWindow( ... ); // and so forth } 4. When an application receives a WM_PAINT message while the window is minimized, draw the icon in the application's client area. The IsIconic function returns TRUE if the application is minimized. The following code demonstrates this step: // In the switch(message) statement of the main window procedure case WM_PAINT: { PAINTSTRUCT ps; if (IsIconic(hWnd)) { BeginPaint(hWnd, (LPPAINTSTRUCT)&ps); // Paint the desktop window background. DefWindowProc(hWnd, WM_ICONERASEBKGND, (WORD)ps.hdc, 0L); // Draw the icon in the cleared area DrawIcon(ps.hdc, 0, 0, hIcon); EndPaint(hWnd, (LPPAINTSTRUCT)&ps); } else // Paint the window as usual } 5. When the user drags an application's icon with the mouse and the application processes the WM_QUERYDRAGICON message as follows, Windows changes the mouse cursor to a black-and-white representation of the application's icon. // In the switch(message) statement of the main window procedure case WM_QUERYDRAGICON: return (LONG)(WORD)hIcon; break; Additional query words: 3.00 3.10 ====================================================================== Keywords : kb16bitonly kbSDKWin16 Technology : kbAudDeveloper kbWin3xSearch kbSDKSearch kbWinSDKSearch kbWinSDK310 Version : WINDOWS:3.1 Issue type : kbhowto ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. Copyright Microsoft Corporation 1999.