Using Owner-Drawn Buttons
The parent window of an owner-drawn button typically responds to at least
three messages for the button:
WM_INITDIALOG,
WM_COMMAND, and
WM_DRAWITEM. It is not necessary to process the
WM_MEASUREITEM message for owner-drawn buttons.
When you must paint an owner-drawn button, Windows sends the parent window a
WM_DRAWITEM message whose
lParam points to a
DRAWITEMSTRUCT structure. Use this structure with all owner-drawn controls to provide the
application with the information it requires to paint the control. The
itemAction and
itemState members of the
DRAWITEMSTRUCT structure define how to paint an owner-drawn button.
The following example shows how to process WM_INITDIALOG, WM_DRAWITEM, and
WM_COMMAND messages for owner-drawn buttons. This example demonstrates how to draw
one of two bitmaps for a control, depending on whether the control is
selected. You would typically use the
wParam parameter of the WM_DRAWITEM message to identify the control; in this
example, only one control is assumed.
LRESULT APIENTRY OwnDrawProc(hDlg, message, wParam, lParam)
HWND hDlg; // window handle of dialog box
UINT message; // type of message
UINT wParam; // message-specific information
LONG lParam;
{
HDC hdcMem;
LPDRAWITEMSTRUCT lpdis;
switch (message) {
case WM_INITDIALOG:
// hinst, hbm1 and hbm2 are defined globally.
hbm1 = LoadBitmap((HANDLE) hinst, "OwnBit1");
hbm2 = LoadBitmap((HANDLE) hinst, "OwnBit2");
return TRUE;
case WM_DRAWITEM:
lpdis = (LPDRAWITEMSTRUCT) lParam;
hdcMem = CreateCompatibleDC(lpdis->hDC);
if (lpdis->itemState & ODS_SELECTED) // if selected
SelectObject(hdcMem, hbm2);
else
SelectObject(hdcMem, hbm1);
// Destination
StretchBlt(
lpdis->hDC, // destination DC
lpdis->rcItem.left, // x upper left
lpdis->rcItem.top, // y upper left
// The next two lines specify the width and
// height.
lpdis->rcItem.right - lpdis->rcItem.left,
lpdis->rcItem.bottom - lpdis->rcItem.top,
hdcMem, // source device context
0, 0, // x and y upper left
32, // source bitmap width
32, // source bitmap height
SRCCOPY); // raster operation
DeleteDC(hdcMem);
return TRUE;
case WM_COMMAND:
if (wParam == IDOK
|| wParam == IDCANCEL) {
EndDialog(hDlg, TRUE);
return TRUE;
}
if (HIWORD(wParam) == BN_CLICKED) {
switch (LOWORD(wParam)) {
case IDB_OWNERDRAW:
.
. // application-defined processing
.
break;
}
}
break;
case WM_DESTROY:
DeleteObject(hbm1); // delete bitmaps
DeleteObject(hbm2);
break;
}
return FALSE;
UNREFERENCED_PARAMETER(lParam);
}
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