CMPT 212 Object-Oriented Applications Design in C++ Fall 1997

Push Button Control

• Pushbutton controls are defined in the resource file.

• The syntax is: PUSHBUTTON text, id, x, y, width, height [, style]
  • Example:

       PUSHBUTTON "Add", IDC_ADD_BUTTON, 30, 12, 50, 14
    	       

• When the user presses a pushbutton, the dialog box containing the pushbutton is sent a WM_COMMAND message, and LOWORD(wParam) contains the id of the pushbutton.
  • Example:

       BOOL CALLBACK DialogFunc(HWND   hwnd,
    			    UINT   message,
    			    WPARAM wParam,
    			    LPARAM lParam) {
       
          switch (message) {
    	
    	 case WM_COMMAND:
    
    	    switch (LOWORD(wParam)) {
    
    	       case IDC_ADD_BUTTON:
    	          ...  // use pressed the "Add" button.
    		  return 1;
    
                   ...
    
    	       }
    
                ...
    
             }
    
          return 0;
       }
    	       

Listbox Control

• A listbox control is a scrollable list of items from which the user can make a selection.

• There are 3 steps to using a listbox:
  1. define it,
  2. initialize it with items,
  3. respond to messages from it.

• There are 2 ways a user can select an item from a listbox:
  1. double-click on an item:
     • A LBN_DBLCLK message is sent to your application.

  2. single-click on an item then press a pushbutton:
     • When the user single-clicks on an item, no message is sent, but the listbox remembers what item was selected.
     • When the user presses the pushbutton, we can query the listbox to determine the currently selected item.

• Example:

• Here is what the resource file contains:

     LISTBOX IDC_DEPT, 16, 10, 60, 45, LBS_NOTIFY | WS_CHILD | 
  	   WS_VISIBLE | WS_BORDER | WS_VSCROLL | WS_TABSTOP
     PUSHBUTTON "Select", IDC_SELECT, 21, 58, 50, 14
  	 

  • These defintions would be inside a dialog box definition.

• Here is what the .h file contains:

     #define IDC_DEPT    101
     #define IDC_SELECT  102
  	 

• When the dialog box is initialized, we must add the items to the listbox.

     BOOL CALLBACK DialogFunc(HWND   hwnd,
  			    UINT   message,
  			    WPARAM wParam,
  			    LPARAM lParam) {
     
        switch (message) {
  	
  	 case WM_INITDIALOG:
  	    SendDlgItemMessage(hwnd, IDC_DEPT, LB_ADDSTRING, 0, (LPARAM) "BISC");
  	    SendDlgItemMessage(hwnd, IDC_DEPT, LB_ADDSTRING, 0, (LPARAM) "CMPT");
  	    SendDlgItemMessage(hwnd, IDC_DEPT, LB_ADDSTRING, 0, (LPARAM) "HIST");
              return 1;
  
           ...
  
           }
  
        return 0;
     }   
           

  • Items will appear in the listbox in the order they are added, unless the listbox is defined to automatically sort the items alphabetically.

• Here is how we respond to messages from the listbox:

     BOOL CALLBACK DialogFunc(HWND   hwnd,
  			    UINT   message,
  			    WPARAM wParam,
  			    LPARAM lParam) {
    
        long i
  
        switch (message) {
  	
  	 case WM_COMMAND:
  
  	    switch (LODWORD(wParam)) {
  
  	       case IDC_DEPT:
  		  if (HIWORD(wParam) == LBN_DBLCLK) {
  		     i = SendDlgItemMessage(hwnd, IDC_DEPT, LB_GETCURSEL, 0, 0L);
  		     ...  // "i" is the item number.
  		     }
  		  return 1;
  
                 case IDC_SELECT:
  		  i = SendDlgItemMessage(hwnd, IDC_DEPT, LB_GETCURSEL, 0, 0L);
  		  if (i > LB_ERR) {
  		     ...  // "i" is the item nubmer.
                       }
                    else {
  		     ...  // no item was selected.
  		     }
                    return 1;
  
                 ...
  
  	       }
  
           ...
  
           }
  
        return 0;
     }   
  	 

  • If SendDlgItemMessage returns LB_ERR, it means that the user has not selected an item.

Other Controls

• A check box control is used to set a boolean value.
  

• A static control is a control that neither receives nor generates messages.
  • A text box is a static control.
    

  • A group box is a static control. A group box draws a box, usually to visually group other controls.
    

• A radio button control is used to model mutually exclusive choices.
  

• A scrollbox control is used when items will not fit into the available space in the window.
  

Modeless Dialog Boxes

• A modeless dialog box allows the user to interact with the parent window while the dialog box is open.

• To create a modeless dialog box, we use CreateDialog instead of DialogBox.

• Unlike the modal dialog box, a modeless dialog box is not automatically visible. We must either:
  • explicitly show it using ShowWindow,
  • add WS_VISIBLE to the STYLE property of the dialog box in the resource file.

• To close a modeless dialog box, we call DestroyWindow instead of EndDialog.

• When our application receives messages, it must determine if they are for the parent window or the dialog box.
  • The function IsDialogMessage determines if a message is for a dialog box.
    • If the message is for the dialog box, the message is sent to the dialog box and IsDialogMessage returns a non-zero value.

    • Otherwise it returns zero.

  • Example:

       HWND hDlg;     // dialog box handle.
    
       int WINAPI WinMain(HINSTANCE hThisInst,
    		      HINSTANCE hPrevInst,
    		      LPSTR     lpszArgs,
    		      int       nWinMode) {
    
          MSG msg;
    
          ...
    
          while (GetMessage(&msg, NULL, 0)) {
    	 if (!IsDialogMessage(hDlg, &msg)) {
    	    TranslateMessage(&msg);
    	    DispatchMessage(&msg);
    	    }
             }
    
          ...
    
       }
    	       

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