Example of Using Custom Check-mark Bitmaps
The example in this topic assigns custom check-mark bitmaps to menu items in
two menus. The menu items in the first menu specify character attributes: bold,
italic, and underline. Each menu item can be either checked or unchecked. For
these menu items, the example uses check-mark bitmaps that resemble the checked
and unchecked states of a check box control.
The menu items in the second menu specify paragraph alignment settings: left,
centered, and right. Only one of these menu items is checked at any given time.
For these menu items, the example uses check-mark bitmaps that resemble the
checked and unchecked states of a radio button control.
The window procedure processes the
WM_CREATE message by calling the application-defined OnCreate function. OnCreate
creates the four check-mark bitmaps and then assigns them to their appropriate menu
items by using the
SetMenuItemBitmaps function.
To create each bitmap, OnCreate calls the application-defined
CreateMenuBitmaps function, specifying a pointer to a bitmap-specific drawing function.
CreateMenuBitmaps creates a monochrome bitmap of the required size, selects it into a
memory device context, and erases the background. Then it calls the specified
drawing function to fill in the foreground.
The four application-defined drawing functions are DrawCheck, DrawUncheck,
DrawRadioCheck, and DrawRadioUncheck. They draw a rectangle with an X, an empty
rectangle, an ellipse containing a smaller filled ellipse, and an empty ellipse,
respectively.
The window procedure processes the
WM_DESTROY message by deleting the check-mark bitmaps. It retrieves each bitmap handle
by using the
GetMenuItemInfo function and then passes the handle to the
DeleteObject function.
When the user chooses a menu item, a
WM_COMMAND message is sent to the owner window. For menu items on the Character menu,
the window procedure calls the application-defined CheckCharacterItem function.
For items on the Paragraph menu, the window procedure calls the
application-defined CheckParagraphItem function.
Each item on the Character menu can be checked and unchecked independently.
Therefore, CheckCharacterItem simply switches the specified menu item's check
state. First, the function calls the
GetMenuItemInfo function to get the current menu item state. Then it switches the MFS_CHECKED
state flag and sets the new state by calling the
SetMenuItemInfo function.
Unlike character attributes, only one paragraph alignment can be selected at a
time. Therefore, CheckParagraphItem checks the specified menu item and removes
the check mark from all other items on the menu. To do so, it calls the
CheckMenuRadioItem function.
Following are the relevant portions of the application's header file.
// Menu-item identifiers for the Character menu
#define IDM_CHARACTER 10
#define IDM_BOLD 11
#define IDM_ITALIC 12
#define IDM_UNDERLINE 13
// Menu-item identifiers for the Paragraph menu
#define IDM_PARAGRAPH 20
#define IDM_LEFT 21
#define IDM_CENTER 22
#define IDM_RIGHT 23
// Function-pointer type for drawing functions
typedef VOID (WINAPI * DRAWFUNC)(HDC hdc, SIZE size);
Following are the relevant portions of the application's window procedure and
related functions.
LRESULT CALLBACK MainWindowProc(
HWND hwnd,
UINT uMsg,
WPARAM wParam,
LPARAM lParam
)
{
switch (uMsg) {
case WM_CREATE:
if (!OnCreate(hwnd))
return -1;
break;
case WM_DESTROY:
OnDestroy(hwnd);
PostQuitMessage(0);
break;
case WM_COMMAND:
switch (LOWORD(wParam)) {
case IDM_BOLD:
case IDM_ITALIC:
case IDM_UNDERLINE:
CheckCharacterItem(hwnd, LOWORD(wParam));
break;
case IDM_LEFT:
case IDM_CENTER:
case IDM_RIGHT:
CheckParagraphItem(hwnd, LOWORD(wParam));
break;
.
. // Process other commands here.
.
}
break;
.
. // Process other messages here.
.
default:
return DefWindowProc(hwnd, uMsg, wParam, lParam);
}
return 0;
}
VOID WINAPI CheckCharacterItem(HWND hwnd, UINT uID)
{
HMENU hmenuBar = GetMenu(hwnd);
HMENU hmenuPopup;
MENUITEMINFO mii;
// Get the handle of the Character menu.
mii.fMask = MIIM_SUBMENU; // information to get
GetMenuItemInfo(hmenuBar, IDM_CHARACTER, FALSE, &mii);
hmenuPopup = mii.hSubMenu;
// Get the state of the specified menu item.
mii.fMask = MIIM_STATE; // information to get
GetMenuItemInfo(hmenuPopup, uID, FALSE, &mii);
// Toggle the checked state.
mii.fState ^= MFS_CHECKED;
SetMenuItemInfo(hmenuPopup, uID, FALSE, &mii);
}
VOID WINAPI CheckParagraphItem(HWND hwnd, UINT uID)
{
HMENU hmenuBar = GetMenu(hwnd);
HMENU hmenuPopup;
MENUITEMINFO mii;
// Get the handle of the Paragraph menu.
mii.fMask = MIIM_SUBMENU; // information to get
GetMenuItemInfo(hmenuBar, IDM_PARAGRAPH, FALSE, &mii);
hmenuPopup = mii.hSubMenu;
// Check the specified item and uncheck all the others.
CheckMenuRadioItem(
hmenuPopup, // handle of menu
IDM_LEFT, // first item in range
IDM_RIGHT, // last item in range
uID, // item to check
MF_BYCOMMAND // IDs, not positions
);
}
BOOL WINAPI OnCreate(HWND hwnd)
{
HMENU hmenuBar = GetMenu(hwnd);
HMENU hmenuPopup;
MENUITEMINFO mii;
UINT uID;
HBITMAP hbmChecked;
HBITMAP hbmUnchecked;
// Get the handle of the Character menu.
mii.fMask = MIIM_SUBMENU; // information to get
GetMenuItemInfo(hmenuBar, IDM_CHARACTER, FALSE, &mii);
hmenuPopup = mii.hSubMenu;
// Create the checked and unchecked bitmaps.
hbmChecked = CreateMenuBitmap(DrawCheck);
hbmUnchecked = CreateMenuBitmap(DrawUncheck);
// Set the checkmark bitmaps for each menu item.
for (uID = IDM_BOLD; uID <= IDM_UNDERLINE; uID++) {
SetMenuItemBitmaps(hmenuPopup, uID, MF_BYCOMMAND,
hbmUnchecked, hbmChecked);
}
// Get the handle of the Paragraph pop-up menu.
mii.fMask = MIIM_SUBMENU; // information to get
GetMenuItemInfo(hmenuBar, IDM_PARAGRAPH, FALSE, &mii);
hmenuPopup = mii.hSubMenu;
// Create the checked and unchecked bitmaps.
hbmChecked = CreateMenuBitmap(DrawRadioCheck);
hbmUnchecked = CreateMenuBitmap(DrawRadioUncheck);
// Set the checkmark bitmaps for each menu item.
for (uID = IDM_LEFT; uID <= IDM_RIGHT; uID++) {
SetMenuItemBitmaps(hmenuPopup, uID, MF_BYCOMMAND,
hbmUnchecked, hbmChecked);
}
// Initially check the IDM_LEFT paragraph item.
CheckMenuRadioItem(hmenuPopup, IDM_LEFT, IDM_RIGHT,
IDM_LEFT, MF_BYCOMMAND);
return TRUE;
}
HBITMAP WINAPI CreateMenuBitmap(DRAWFUNC lpfnDraw)
{
// Create a DC compatible with the desktop window's DC.
HWND hwndDesktop = GetDesktopWindow();
HDC hdcDesktop = GetDC(hwndDesktop);
HDC hdcMem = CreateCompatibleDC(hdcDesktop);
// Determine the required bitmap size.
DWORD dwExt = GetMenuCheckMarkDimensions();
SIZE size = { LOWORD(dwExt), HIWORD(dwExt) };
// Create a monochrome bitmap and select it.
HBITMAP hbm = CreateBitmap(size.cx, size.cy, 1, 1, NULL);
HBITMAP hbmOld = SelectObject(hdcMem, hbm);
// Erase the background and call the drawing function.
PatBlt(hdcMem, 0, 0, size.cx, size.cy, WHITENESS);
(*lpfnDraw)(hdcMem, size);
// Clean up.
SelectObject(hdcMem, hbmOld);
DeleteDC(hdcMem);
ReleaseDC(hwndDesktop, hdcDesktop);
return hbm;
}
VOID WINAPI DrawCheck(HDC hdc, SIZE size)
{
HBRUSH hbrOld;
hbrOld = SelectObject(hdc, GetStockObject(NULL_BRUSH));
Rectangle(hdc, 0, 0, size.cx, size.cy);
MoveToEx(hdc, 0, 0, NULL);
LineTo(hdc, size.cx, size.cy);
MoveToEx(hdc, 0, size.cy - 1, NULL);
LineTo(hdc, size.cx - 1, 0);
SelectObject(hdc, hbrOld);
}
VOID WINAPI DrawUncheck(HDC hdc, SIZE size)
{
HBRUSH hbrOld;
hbrOld = SelectObject(hdc, GetStockObject(NULL_BRUSH));
Rectangle(hdc, 0, 0, size.cx, size.cy);
SelectObject(hdc, hbrOld);
}
VOID WINAPI DrawRadioCheck(HDC hdc, SIZE size)
{
HBRUSH hbrOld;
hbrOld = SelectObject(hdc, GetStockObject(NULL_BRUSH));
Ellipse(hdc, 0, 0, size.cx, size.cy);
SelectObject(hdc, GetStockObject(BLACK_BRUSH));
Ellipse(hdc, 2, 2, size.cx - 2, size.cy - 2);
SelectObject(hdc, hbrOld);
}
VOID WINAPI DrawRadioUncheck(HDC hdc, SIZE size)
{
HBRUSH hbrOld;
hbrOld = SelectObject(hdc, GetStockObject(NULL_BRUSH));
Ellipse(hdc, 0, 0, size.cx, size.cy);
SelectObject(hdc, hbrOld);
}
VOID WINAPI OnDestroy(HWND hwnd)
{
HMENU hmenuBar = GetMenu(hwnd);
HMENU hmenuPopup;
MENUITEMINFO mii;
// Get the handle of the Character menu.
mii.fMask = MIIM_SUBMENU; // information to get
GetMenuItemInfo(hmenuBar, IDM_CHARACTER, FALSE, &mii);
hmenuPopup = mii.hSubMenu;
// Get the check-mark bitmaps and delete them.
mii.fMask = MIIM_CHECKMARKS;
GetMenuItemInfo(hmenuPopup, IDM_BOLD, FALSE, &mii);
DeleteObject(mii.hbmpChecked);
DeleteObject(mii.hbmpUnchecked);
// Get the handle of the Paragraph menu.
mii.fMask = MIIM_SUBMENU; // information to get
GetMenuItemInfo(hmenuBar, IDM_PARAGRAPH, FALSE, &mii);
hmenuPopup = mii.hSubMenu;
// Get the check-mark bitmaps and delete them.
mii.fMask = MIIM_CHECKMARKS;
GetMenuItemInfo(hmenuPopup, IDM_LEFT, FALSE, &mii);
DeleteObject(mii.hbmpChecked);
DeleteObject(mii.hbmpUnchecked);
}
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