Lecture 7 Menu, controls, scroll bars

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)

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; }

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

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

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

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.

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

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

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

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 );

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

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

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 );

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 Scroll bars

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 ); Standard scroll bar

// 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 ); Scroll bar controls

Scroll bar sends WM_HSCROLL or WM_VSCROLL messages wParam can take one of the following values: SB_ENDSCROLL SB_LEFT SB_RIGHT SB_LINELEFT SB_LINERIGHT SB_PAGELEFT SB_PAGERIGHT SB_THUMBPOSITION SB_THUMBTRACK lParam handle to the scroll bar control (or NULL) Scroll bar messages

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 Handling scroll bars