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Lecture 7

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Lecture 7

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  1. Lecture 7 Menu, controls, scroll bars

  2. Menu • Menu item sends WM_COMMAND message to the application window • Menu is attached to window when the window is created • Menu can be created using Visual C++ Resource Editor • Menu can be modified at run time: • Items can be disabled, enabled, checked (EnableMenuItem, CheckMenuItem, CheckMenuRadioItem) • Items can be added and removed as required (AppendMenu, DeleteMenu, RemoveMenu) • Menu item can be modified (ModifyMenu)

  3. WM_COMMAND handler: • case WM_COMMAND: • wmId = LOWORD(wParam); • wmEvent = HIWORD(wParam); • // Parse the menu selections: • switch (wmId) • { • case IDM_ABOUT: • DialogBox(hInst, (LPCTSTR)IDD_ABOUTBOX, • hWnd, (DLGPROC)About); • break; • case IDM_EXIT: • DestroyWindow(hWnd); • break; • default: • return DefWindowProc(hWnd, message, • wParam, lParam); • } • break; • }

  4. Menu functions: • LoadMenu – load menu from resources • GetMenu – get menu handle from window handle • GetSystemMenu – get handle to system menu (menu that has Minimize, Restore, Close commands) • SetMenu – set (or replace) window menu • CreateMenu, CreatePopupMenu – create dynamically new menu instead of loading it from resources • TrackPopupMenu, TrackPopupMenuEx – display and track poupu menu on the screen

  5. Menu functions (cont): • GetMenuItemCount – returns number of items in the specified menu • GetMenuItemID – get menu item ID (command ID assigned to that menu item) • GetMenuItemInfo – get information about menu item • GetMenuState – get state of the menu item (if it is checked, disabled, grayed etc.) • GetMenuString – get menu item string

  6. Menu functions (cont): • InsertMenuItem – insert new menu item or sub-menu to the menu • AppendMenu – add new item or sub-menu at the end of the menu • CheckMenuItem – add or remove check mark from menu item • CheckMenuRadioItem – position check mark on a group of menu items • SetMenuItemInfo – modify menu item • RemoveMenu – remove menu item or detach sub-menu from the specified menu

  7. WM_COMMAND message • wParam • The high-order word specifies the notification code if the message is from a control. If the message is from an accelerator, this value is 1. If the message is from a menu, this value is zero. • The low-order word specifies the identifier of the menu item, control, or accelerator. • lParam • Handle to the control sending the message if the message is from a control. Otherwise, this parameter is NULL.

  8. Controls • Control - child window that specializes in some task, e.g.: • button control - can be pressed • list control - presents list of values • edit control - allows user to enter some text • Control must have parent window (because it is a child window) • Control notifies its parent when important event occurs, e.g. • button control notifies parent when it is pressed • list control notifies parent when selection changes • edit control notifies parent every time the text inside the control changes

  9. Controls • Notifications by controls are done using SendMessage function • Standard (predefined) controls send WM_COMMAND as the notification message

  10. Predefined controls • BUTTON – button control. This includes: • push buttons • checkboxes • radio buttons • LISTBOX – list control • COMBOBOX – drop down list control • EDIT – edit control (for editing text) • STATIC – static text (usually label for other control) • RichEdit, RICHEDIT_CLASS – rich edit control • SCROLLBAR – scroll bar control

  11. Creating predefined control HWND hWndButton = CreateWindowEx( 0, // extended style "BUTTON", // predefined class name "Button text", // button text WS_CHILD | WS_VISIBLE | BS_PUSHBUTTON, // style 100, 100, // position 70, 30, // size hWndParent, // parent window (HMENU)102, // control identifier hInstance, // instance hande NULL );

  12. WM_COMMAND messages sent by this button will have: • lParam == hWndButton • LOWORD( wParam ) == 102 // (control id) • HIWORD( wParam ) == notification code, e.g.: • BN_CLICKED - button was clicked • BN_DOUBLECLICKED • BN_KILLFOCUS • BN_SETFOCUS

  13. Customizing predefined controls • To customize predefined control: • Use one of predefined styles for that control (when creating control), e.g: • buttons - BS_PUSHBUTTON, BS_RADIOBUTTON • edit controls - ES_READONLY, ES_UPPERCASE • Send message to the control, e.g. • list boxes - LB_ADDSTRING, LB_RESETCONTENT • edit controls - EM_GETLINE, EM_GETLINECOUNT, EM_GETSEL

  14. HWND hWndListBox = CreateWindowEx( 0, "LISTBOX", // class name "", // window title WS_CHILD | WS_VISIBLE, // style 100, 100, // position 170, 150, // size hWndParent, // parent window handle (HMENU)103, // control identifier hInstance, // instance handle NULL ); SendMessage( hWndListBox, LB_ADDSTRING, 0, (LPARAM)"First Item" ); SendMessage( hWndListBox, LB_ADDSTRING, 0, (LPARAM)"Second Item" ); SendMessage( hWndListBox, LB_SETCURSEL, 1, 0 );

  15. Scroll bars • Can be created in two ways: • as a scroll bar attached to a window (standard scroll bar) • as a control using „SCROLLBAR” class • Standard scroll bar is created automatically and: • it is automatically resized/moved when the window is resized • it is created on non-client area of the window • it does not have window handle • Scroll bar control must be: • manually created, moved and resized • it does have normal window handle • it is created on its parent window client area

  16. Standard scroll bar • To create window with scroll bars: hWnd = CreateWindow(szWindowClass, szTitle, WS_OVERLAPPEDWINDOW | WS_HSCROLL | WS_VSCROLL, CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, NULL, NULL, hInstance, NULL); SCROLLINFO si; si.cbSize = sizeof( si ); si.fMask = SIF_ALL; si.nMin = 0; // minimum scrollbar position si.nMax = 100; // maximum scrollbar position si.nPos = 50; // current scrollbar position si.nPage = 10; // page size SetScrollInfo( hWnd, SB_HORZ, &si, false );

  17. Scroll bar controls // horizontal scroll bar CreateWindow( "SCROLLBAR", "", WS_CHILD | WS_VISIBLE, 30, 50, 100, 20, hWnd, (HMENU)100, hInstance, NULL ); // vertical scroll bar CreateWindow( "SCROLLBAR", "", WS_CHILD | WS_VISIBLE | SBS_VERT, 30, 80, 20, 100, hWnd, (HMENU)101, hInstance, NULL );

  18. Scroll bar messages • Scroll bar sends WM_HSCROLL or WM_VSCROLL messages • wParamcan take one of the following values: • SB_ENDSCROLL • SB_LEFT • SB_RIGHT • SB_LINELEFT • SB_LINERIGHT • SB_PAGELEFT • SB_PAGERIGHT • SB_THUMBPOSITION • SB_THUMBTRACK • lParamhandle to the scroll bar control (or NULL)

  19. Handling scroll bars • Application is responsible for: • Setting scroll bar sizes (SetScrollInfo function) • Handling scroll bar messages (e.g. WM_HSCROLL) • application should move scrollbar position (using SetScrollInfo or SetScrollPos) • remember current scrollbar position in some variable • invalidate the window • Drawing window content scrolled by scrollbar position • Application can scroll window content using ScrollWindow, ScrollWindowEx or ScrollDC functions and then invalidate only portion of the window