Creating an Owner-Drawn List Box

The following example 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_OWNERDRAW and LBS_HASSTRINGS styles, in addition to the standard list box styles. The code initializes the list box 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 80

#define YBITMAP 20

#define BUFFER MAX_PATH

HBITMAP hbmpPencil, hbmpCrayon, hbmpMarker, hbmpPen, hbmpFork;

HBITMAP hbmpPicture, hbmpOld;

• oid AddItem(HWND hwnd, LPSTR lpstr, HBITMAP hbmp)

{

int nItem;

nItem = SendMessage(hwndList, LB_ADDSTRING, 0, lpstr);

SendMessage(hwndList, LB_SETITEMDATA, nItem, hbmp);

}

DWORD APIENTRY DlgDrawProc(

HWND hDlg, /* window handle of dialog box */

UINT message, /* type of message */

UINT wParam, /* message-specific information */

LONG lParam)

{

int nItem;

TCHAR tchBuffer[BUFFER];

HBITMAP hbmp;

HWND hListBox;

TEXTMETRIC tm;

int y;

HDC hdcMem;

LPMEASUREITEMSTRUCT lpmis;

LPDRAWITEMSTRUCT lpdis;

RECT rcBitmap;

switch (message) {

case WM_INITDIALOG:

/* Load bitmaps. */

hbmpPencil = LoadBitmap(hinst, MAKEINTRESOURCE(700));

hbmpCrayon = LoadBitmap(hinst, MAKEINTRESOURCE(701));

hbmpMarker = LoadBitmap(hinst, MAKEINTRESOURCE(702));

hbmpPen = LoadBitmap(hinst, MAKEINTRESOURCE(703));

hbmpFork = LoadBitmap(hinst, MAKEINTRESOURCE(704));

/* Retrieve list box handle. */

hListBox = GetDlgItem(hDlg, IDL_STUFF);

/*

* Initialize the list box text and associate a bitmap

* with each list box item.

*/

AddItem(hListBox, "pencil", hbmpPencil);

AddItem(hListBox, "crayon", hbmpCrayon);

AddItem(hListBox, "marker", hbmpMarker);

AddItem(hListBox, "pen", hbmpPen);

AddItem(hListBox, "fork", hbmpFork);

SetFocus(hListBox);

SendMessage(hListBox, LB_SETCURSEL, 0, 0);

return TRUE;

case WM_MEASUREITEM:

lpmis = (LPMEASUREITEMSTRUCT) lParam;

/* Set the height of the list box items. */

lpmis->itemHeight = 20;

return TRUE;

case WM_DRAWITEM:

lpdis = (LPDRAWITEMSTRUCT) lParam;

/* If there are no list box items, skip this message. */

if (lpdis->itemID == -1) {

break;

}

/*

* Draw the bitmap and text for the list box item. Draw a

* rectangle around the bitmap if it is selected.

*/

switch (lpdis->itemAction) {

case ODA_SELECT:

case ODA_DRAWENTIRE:

/* Display the bitmap associated with the item. */

hbmpPicture = (HBITMAP) SendMessage(lpdis->hwndItem,

LB_GETITEMDATA, lpdis->itemID, (LPARAM) 0);

hdcMem = CreateCompatibleDC(lpdis->hDC);

hbmpOld = SelectObject(hdcMem, hbmpPicture);

BitBlt(lpdis->hDC,

lpdis->rcItem.left, lpdis->rcItem.top,

lpdis->rcItem.right - lpdis->rcItem.left,

lpdis->rcItem.bottom - lpdis->rcItem.top,

hdcMem, 0, 0, SRCCOPY);

/* Display the text associated with the item. */

SendMessage(lpdis->hwndItem, LB_GETTEXT,

lpdis->itemID, (LPARAM) tchBuffer);

GetTextMetrics(lpdis->hDC, &tm);

y = (lpdis->rcItem.bottom + lpdis->rcItem.top -

tm.tmHeight) / 2;

TextOut(lpdis->hDC,

XBITMAP + 6,

y,

tchBuffer,

strlen(tchBuffer));

SelectObject(hdcMem, hbmpOld);

DeleteDC(hdcMem);

/* Is the item selected? */

if (lpdis->itemState & ODS_SELECTED) {

/*

* Set RECT coordinates to surround only the

* bitmap.

*/

rcBitmap.left = lpdis->rcItem.left;

rcBitmap.top = lpdis->rcItem.top;

rcBitmap.right = lpdis->rcItem.left + XBITMAP;

rcBitmap.bottom = lpdis->rcItem.top + YBITMAP;

/*

* Draw a rectangle around bitmap to indicate

* the selection.

*/

DrawFocusRect(lpdis->hDC, &rcBitmap);

}

break;

case ODA_FOCUS:

/*

* Do not process focus changes. The focus caret

* (outline rectangle) indicates the selection.

* The Which one? (IDOK) button indicates the final

* selection.

*/

break;

}

return TRUE;

case WM_COMMAND:

switch (LOWORD(wParam)) {

case IDOK:

/* Get the selected item's text. */

nItem = SendMessage(GetDlgItem(hDlg, IDL_STUFF),

LB_GETCURSEL, 0, (LPARAM) 0);

hbmp = SendMessage(GetDlgItem(hDlg, IDL_STUFF),

LB_GETITEMDATA, nItem, 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, "Try again!", "Oops.", MB_OK);

return FALSE;

}

else {

MessageBox(hDlg, "You're right!",

"Congratulations.", MB_OK);

/* Fall through. */

}

case IDCANCEL:

/* Destroy the dialog box. */

EndDialog(hDlg, TRUE);

return TRUE;

default:

return FALSE;

}

case WM_DESTROY:

/* Free any resources used by the bitmaps. */

DeleteObject(hbmpPencil);

DeleteObject(hbmpCrayon);

DeleteObject(hbmpMarker);

DeleteObject(hbmpPen);

DeleteObject(hbmpFork);

return TRUE;

default:

return FALSE;

}

return FALSE;

}

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