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15.1 Z-Order
- The Z order of a window indicates the window's position in a stack of overlapping windows. This window stack is oriented along an imaginary axis, the z-axis, extending outward from the screen.
- The window at the top of the Z order overlaps all other windows.
- The window at the bottom of the Z order is overlapped by all other windows.
15.2 Windows Review
15.2.1 CreateWindow
CreateWindow function have been discussing in our previous lectures. Much of its details including styles, class name, parent handles, instance handle and coordinates, etc have been discussed in chapter 11. CreateWindow Function is used to create window. CreateWindow function can create parent, child, popup and overlapped windows with dimensions x, y, width and height.
HWND CreateWindow ( LPCTSTR lpClassName, // registered class name LPCTSTR lpWindowName, // window name DWORD dwStyle, // window style int x, // horizontal position of window int y, // vertical position of window int nWidth, // window width int nHeight, // window height HWND hWndParent, // handle to parent or owner window HMENU hMenu, // menu handle or child identifier HINSTANCE hInstance, // handle to application instance LPVOID lpParam // window-creation data );
15.2.2 Child Windows
Following are the characteristics of child windows.
- A child window always appears within the client area of its parent window.
- Child windows are most often as controls.
- A child window sends WM_COMMAND notification messages to its parent window.
- When a child window is created a unique identifier for that window is specified in hMenu parameter of CreateWindow()
15.2.3 Window Procedure
LRESULT CALLBACK WindowProc ( HWND hwnd, // handle to window UINT uMsg, // WM_COMMAND WPARAM wParam, // notification code and identifier LPARAM lParam // handle to control (HWND) );
15.2.4 Notification code
Common controls are normally taken as child windows that send notification messages to the parent window when events, such as input from the user, occur in the control. The application relies on these notification messages to determine what action the user wants it to take. Except for trackbars, which use the WM_HSCROLL and WM_VSCROLL messages to notify their parent of changes, common controls send notification messages as WM_NOTIFY messages.
15.2.5 WM_COMMAND Notification code
- The wParam parameter of Window Procedure contains the notification code and control identifier.
- low word: ID of the control n high word: notification code
- BUTTON BN_CLICKED
- EDIT EN_CHANGE etc
15.3 Example Application
For demonstration purpose we are going to create an example application.
15.3.1 Description
Our application will be parent-child window application. This application will consist of three push buttons of names:
- RECTANGLE
- CIRCLE
- MESSAGE”
15.3.4 Window classes
The Window classes used in this application are:
- mainWindowClass
- popupWindowClass
- System Window Classes
15.3.4.1 Main Window class
wc.lpfnWndProc = mainWindowProc; wc.hInstance = hAppInstance = hInstance; wc.hCursor = LoadCursor(NULL, IDC_UPARROW); wc.hbrBackground= (HBRUSH)GetStockObject (GRAY_BRUSH); wc.lpszClassName= "MainWindowClass";
if(!RegisterClass(&wc)) { return 0; }
15.3.4.2 Popup Window class
wc .lpfnWndProc = popupWindowProc; wc.hbrBackground = (HBRUSH)(COLOR_WINDOW+1); wc.hCursor = LoadCursor(NULL, IDC_HELP); wc.lpszClassName = "PopupWindowClass";
if(!RegisterClass(&wc)) { return 0; }
15.3.4.3 System Window classes
System window classes are pre-registered. They do not need to register in our application. In this application, we will only used to create them not to register them.
15.3.5 Creating Main Windows
Create a Main Window of the Application.
hWndMain = CreateWindow("MainWindowClass", "Virtual University",
WS_OVERLAPPEDWINDOW | WS_VISIBLE,
NULL, NULL, hInstance, NULL );
// check the returned handle, don’t need to proceed if the returned handle is NULL if(!hWnd) { MessageBox(NULL,”Cannot Create Main Window”,”Error”, MB_ICONHAND|MB_OK); return 0; }
Now create a popup window with caption and visible style bit on.
hWndPopup = CreateWindow("PopupWindowClass", //window name (optional) "Popup Window", //class name WS_POPUP | WS_CAPTION | WS_VISIBLE, 250, 250, 300, 250, hWndMain, NULL, hInstance, NULL );
15.3.6 Creating Child Windows
Create a button window bearing a text “Rectangle”.
hWndButton=CreateWindow("BUTTON", "Rectangle", WS_CHILD | WS_VISIBLE, 10, 10, 100, 50, hWndMain, 5, hInstance, NULL );
Create an Edit Window bearing a text “Message”
CreateWindow("EDIT", "Message", WS_CHILD | WS_VISIBLE n | ES_LOWERCASE, 10, 190, 200, 25, hWndMain, 8, hInstance, NULL );
here we check the button if button rectangle is pressed then draw a rectangle with Light Gray stock brush.
case WM_DRAW_FIGURE:
hDC = GetDC(hWndPopup); switch(wParam) { case RECTANGLE: SelectObject(hDC,GetStockObject( LTGRAY_BRUSH)); Rectangle(hDC, 50, 10, 230, 150); break; }
15.3.8.2 Drawing in Popup Window- II
In case of Circle, we create hatch brush, we created a hatch brush which has a style of diagonal cross lines. After creating a hatch brush we select it on device context to draw a figure. After drawing, brush must be deleted.
case CIRCLE:
hBrush = CreateHatchBrush(HS_DIAGCROSS, RGB(170, 150, 180)); SelectObject(hDC, hBrush); Ellipse(hDC, 70, 10, 210, 150); DeleteObject(hBrush); break;
15.3.8.3 Drawing in Popup Window- III
By pressing the button a text must be display with the stock object Ansi variable fonts and background brush. Text are displayed using TextOut GDI function.
case TEXT_MESSAGE: { TextOut(hDC, 50, 100, "Virtual University", 18); SelectObject(hDC, GetStockObject( ANSI_VAR_FONT)); SetBkColor(hDC, RGB(10, 255, 20)); TextOut(hDC, 50, 115, "knowledge Beyond Boundaries", 27); break; }
ReleaseDC(hWndPopup, hDC);
15.3.9 Informing back to Main Window
case WM_DRAW_FIGURE:
hDC = GetDC(hWndPopup); hwndEdit = GetDlgItem(GetParent(hWnd), 8);
switch(wParam) { case RECTANGLE: SelectObject(hDC,GetStockObject(LTGRAY_BRUSH)); Rectangle(hDC, 50, 10, 230, 150); SendMessage(hwndEdit, WM_SETTEXT, 0, "Rectangle DrAwN!"); break; }
15.3.10 Quit Application via control in Popup window
Main window is destroyed through button’s notification message BN_CLICKED. Main Window can be destroyed using DestroyWindow Function.
WM_CREATE: CreateWindow("BUTTON", "Quit Application", WS_CHILD | WS_VISIBLE, n 75, 155, 150, 40, hWnd, 1234, hAppInstance, NULL); break;
case WM_COMMAND: wControlID = LOWORD(wParam); wNotificationCode = HIWORD(wParam); if(wNotificationCode == BN_CLICKED) { switch(wControlID) { case 1234: DestroyWindow(GetParent(hWnd)); break; }
}
