How to Create an Owner-Drawn List Box
This topic demonstrates how to implement an owner-drawn list box.
The C++ code example in this topic shows how to draw a list box that contains five owner-drawn items: four drawing implements and a fork. Each list item appears as a bitmap followed by the name of the object. A button prompts the user to select one item that is not like the others. Choosing the button with the fork selected displays a "You're right!" message and closes the dialog box. Choosing the button with any other list item selected displays a "Try again!" message.
The list box has the LBS_OWNERDRAWFIXED and LBS_HASSTRINGS styles, in addition to the standard list box styles.
What you need to know
Technologies
Prerequisites
- C/C++
- Windows User Interface Programming
Instructions
To initialize an owner-drawn list box, your application must load the text string and associated bitmap for each list box item.
In the following C++ code example, the dialog box procedure initializes the list box, IDC_LIST_STUFF, by sending the LB_ADDSTRING message to set the text, and then sends the LB_SETITEMDATA message to associate a bitmap with each list box item. The code also sets the height of each list box item by processing the WM_MEASUREITEM message and draws the text and bitmap for each item by processing the WM_DRAWITEM message.
#define XBITMAP 48
#define YBITMAP 48
#define BUFFER MAX_PATH
HBITMAP hbmpPencil, hbmpCrayon, hbmpMarker, hbmpPen, hbmpFork;
HBITMAP hbmpPicture, hbmpOld;
void AddItem(HWND hwnd, PTSTR pstr, HBITMAP hbmp)
{
int lbItem;
lbItem = SendMessage(hwnd, LB_ADDSTRING, 0, (LPARAM)pstr);
SendMessage(hwnd, LB_SETITEMDATA, (WPARAM)lbItem, (LPARAM)hbmp);
}
INT_PTR CALLBACK DlgDrawProc(HWND hDlg, UINT message,
UINT wParam, LONG lParam)
{
HWND hListBox;
PMEASUREITEMSTRUCT pmis;
PDRAWITEMSTRUCT pdis;
HDC hdcMem;
HBITMAP hbmp;
TCHAR achBuffer[BUFFER];
size_t cch;
int yPos;
int lbItem;
TEXTMETRIC tm;
RECT rcBitmap;
HRESULT hr;
switch (message)
{
case WM_INITDIALOG:
// Load the bitmaps. g_hInst is the global HINSTANCE handle.
hbmpPencil = LoadBitmap(g_hInst, MAKEINTRESOURCE(IDB_PENCIL));
hbmpCrayon = LoadBitmap(g_hInst, MAKEINTRESOURCE(IDB_CRAYON));
hbmpMarker = LoadBitmap(g_hInst, MAKEINTRESOURCE(IDB_MARKER));
hbmpPen = LoadBitmap(g_hInst, MAKEINTRESOURCE(IDB_PEN));
hbmpFork = LoadBitmap(g_hInst, MAKEINTRESOURCE(IDB_FORK));
// Retrieve the list box handle.
hListBox = GetDlgItem(hDlg, IDC_LIST_STUFF);
// Initialize the list box text and associate a bitmap
// with each list box item.
AddItem(hListBox, L"pencil", hbmpPencil);
AddItem(hListBox, L"crayon", hbmpCrayon);
AddItem(hListBox, L"marker", hbmpMarker);
AddItem(hListBox, L"pen", hbmpPen);
AddItem(hListBox, L"fork", hbmpFork);
SetFocus(hListBox);
SendMessage(hListBox, LB_SETCURSEL, 0, 0);
return TRUE;
case WM_MEASUREITEM:
pmis = (PMEASUREITEMSTRUCT) lParam;
// Set the height of the list box items.
pmis->itemHeight = YBITMAP;
return TRUE;
case WM_DRAWITEM:
pdis = (PDRAWITEMSTRUCT) lParam;
// If there are no list box items, skip this message.
if (pdis->itemID == -1)
{
break;
}
// Draw the bitmap and text for the list box item. Draw a
// rectangle around the bitmap if it is selected.
switch (pdis->itemAction)
{
case ODA_SELECT:
case ODA_DRAWENTIRE:
// Draw the bitmap associated with the item.
//
// Get the item bitmap.
hbmpPicture = (HBITMAP)SendMessage(pdis->hwndItem,
LB_GETITEMDATA, pdis->itemID, 0);
// Create a compatible device context.
hdcMem = CreateCompatibleDC(pdis->hDC);
// Select the item bitmap into the compatible device
// context and save the old bitmap.
hbmpOld = (HBITMAP) SelectObject(hdcMem, hbmpPicture);
// Copy the bitmap into the compatible device context.
BitBlt(pdis->hDC,
pdis->rcItem.left, pdis->rcItem.top,
pdis->rcItem.right - pdis->rcItem.left,
pdis->rcItem.bottom - pdis->rcItem.top,
hdcMem, 0, 0, SRCCOPY);
// Draw the string associated with the item.
//
// Get the item string from the list box.
SendMessage(pdis->hwndItem, LB_GETTEXT,
pdis->itemID, (LPARAM)achBuffer);
// Get the metrics for the current font.
GetTextMetrics(pdis->hDC, &tm);
// Calculate the vertical position for the item string
// so that the string will be vertically centered in the
// item rectangle.
yPos = (pdis->rcItem.bottom + pdis->rcItem.top -
tm.tmHeight) / 2;
// Get the character length of the item string.
hr = StringCchLength(achBuffer, BUFFER, &cch);
if (FAILED(hr))
{
// TODO: Handle error.
}
// Draw the string in the item rectangle, leaving a six
// pixel gap between the item bitmap and the string.
TextOut(pdis->hDC, XBITMAP + 6, yPos, achBuffer, cch);
// Clean up.
SelectObject(hdcMem, hbmpOld);
DeleteDC(hdcMem);
// Is the item selected?
if (pdis->itemState & ODS_SELECTED)
{
// Set RECT coordinates to surround only the
// bitmap.
rcBitmap.left = pdis->rcItem.left;
rcBitmap.top = pdis->rcItem.top;
rcBitmap.right = pdis->rcItem.left + XBITMAP;
rcBitmap.bottom = pdis->rcItem.top + YBITMAP;
// Draw a rectangle around bitmap to indicate
// the selection.
DrawFocusRect(pdis->hDC, &rcBitmap);
}
break;
case ODA_FOCUS:
// Do not process focus changes. The focus caret
// (outline rectangle) indicates the selection.
// The IDOK button indicates the final
// selection.
break;
}
return TRUE;
case WM_COMMAND:
switch (LOWORD(wParam))
{
case IDOK:
// Get the selected item's text.
lbItem = SendMessage(GetDlgItem(hDlg, IDC_LIST_STUFF),
LB_GETCURSEL, 0, 0);
// Get the selected item's bitmap.
hbmp = (HBITMAP) SendMessage(GetDlgItem(hDlg, IDC_LIST_STUFF),
LB_GETITEMDATA, lbItem, 0);
// If the item is not the correct answer, tell the
// user to try again.
//
// If the item is the correct answer, congratulate
// the user and destroy the dialog box.
if (hbmp != hbmpFork)
{
MessageBox(hDlg, L"Try again!", L"Oops", MB_OK);
return FALSE;
}
else
{
MessageBox(hDlg, L"You're right!",
L"Congratulations.", MB_OK);
// Fall through.
}
case IDCANCEL:
// Destroy the dialog box.
EndDialog(hDlg, TRUE);
return TRUE;
default:
return FALSE;
}
case WM_DESTROY:
// Free the bitmap resources.
DeleteObject(hbmpPencil);
DeleteObject(hbmpCrayon);
DeleteObject(hbmpMarker);
DeleteObject(hbmpPen);
DeleteObject(hbmpFork);
return TRUE;
default:
return FALSE;
}
return FALSE;
}
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