自绘控件之DrawItem(LPDRAWITEMSTRUCT )

1.自绘函数：

virtual void DrawItem(   LPDRAWITEMSTRUCT lpDrawItemStruct );

Parameters

lpDrawItemStruct

A long pointer to a DRAWITEMSTRUCT structure. The structure contains information about the item to be drawn and the type of drawing required.

An owner-drawn button has the BS_OWNERDRAW style set. Override this member function to implement drawing for an owner-drawnCButton object. The application should restore all graphics device interface (GDI) objects selected for the display context supplied inlpDrawItemStruct before the member function terminates.

Also see the BS_ style values.

2：函数的结构体

The DRAWITEMSTRUCT structure provides information the owner window must have to determine how to paint an owner-drawn control or menu item.

 

typedef struct tagDRAWITEMSTRUCT {   UINT CtlType;   UINT CtlID;   UINT itemID;   UINT itemAction;   UINT itemState;   HWND hwndItem;   HDC hDC;   RECT rcItem;   DWORD itemData;} DRAWITEMSTRUCT;

Parameters

CtlType

The control type. The values for control types are as follows:

• ODT_BUTTON   Owner-drawn button

• ODT_COMBOBOX   Owner-drawn combo box

• ODT_LISTBOX   Owner-drawn list box

• ODT_MENU   Owner-drawn menu

• ODT_LISTVIEW   List view control

• ODT_STATIC   Owner-drawn static control

• ODT_TAB   Tab control

CtlID

The control ID for a combo box, list box, or button. This member is not used for a menu.

itemID

The menu-item ID for a menu or the index of the item in a list box or combo box. For an empty list box or combo box, this member is a negative value, which allows the application to draw only the focus rectangle at the coordinates specified by thercItem member even though there are no items in the control. The user can thus be shown whether the list box or combo box has the input focus. The setting of the bits in theitemAction member determines whether the rectangle is to be drawn as though the list box or combo box has input focus.

itemAction

Defines the drawing action required. This will be one or more of the following bits:

• ODA_DRAWENTIRE   This bit is set when the entire control needs to be drawn.

• ODA_FOCUS   This bit is set when the control gains or loses input focus. TheitemState member should be checked to determine whether the control has focus.

• ODA_SELECT   This bit is set when only the selection status has changed. TheitemState member should be checked to determine the new selection state.

itemState

Specifies the visual state of the item after the current drawing action takes place. That is, if a menu item is to be dimmed, the state flagODS_GRAYED will be set. The state flags are as follows:

• ODS_CHECKED   This bit is set if the menu item is to be checked. This bit is used only in a menu.

• ODS_DISABLED   This bit is set if the item is to be drawn as disabled.

• ODS_FOCUS   This bit is set if the item has input focus.

• ODS_GRAYED   This bit is set if the item is to be dimmed. This bit is used only in a menu.

• ODS_SELECTED   This bit is set if the item's status is selected.

• ODS_COMBOBOXEDIT   The drawing takes place in the selection field (edit control) of an ownerdrawn combo box.

• ODS_DEFAULT   The item is the default item.

hwndItem

Specifies the window handle of the control for combo boxes, list boxes, and buttons. Specifies the handle of the menu (HMENU) that contains the item for menus.

hDC

Identifies a device context. This device context must be used when performing drawing operations on the control.

rcItem

A rectangle in the device context specified by the hDC member that defines the boundaries of the control to be drawn. Windows automatically clips anything the owner draws in the device context for combo boxes, list boxes, and buttons, but it does not clip menu items. When drawing menu items, the owner must not draw outside the boundaries of the rectangle defined by thercItem member.

itemData

For a combo box or list box, this member contains the value that was passed to the list box by one of the following:

3：例子

 NOTE: CMyButton is a class derived from CButton. The CMyButton// object was created as follows://// CMyButton myButton;// myButton.Create(_T("My button"), //      WS_CHILD|WS_VISIBLE|BS_PUSHBUTTON|BS_OWNERDRAW, //      CRect(10,10,100,30), pParentWnd, 1);//// This example implements the DrawItem method for a CButton-derived // class that draws the button's text using the color red.void CMyButton::DrawItem(LPDRAWITEMSTRUCT lpDrawItemStruct) {   UINT uStyle = DFCS_BUTTONPUSH;   // This code only works with buttons.   ASSERT(lpDrawItemStruct->CtlType == ODT_BUTTON);   // If drawing selected, add the pushed style to DrawFrameControl.   if (lpDrawItemStruct->itemState & ODS_SELECTED)      uStyle |= DFCS_PUSHED;   // Draw the button frame.   ::DrawFrameControl(lpDrawItemStruct->hDC, &lpDrawItemStruct->rcItem,       DFC_BUTTON, uStyle);   // Get the button's text.   CString strText;   GetWindowText(strText);   // Draw the button text using the text color red.   COLORREF crOldColor = ::SetTextColor(lpDrawItemStruct->hDC, RGB(255,0,0));   ::DrawText(lpDrawItemStruct->hDC, strText, strText.GetLength(),       &lpDrawItemStruct->rcItem, DT_SINGLELINE|DT_VCENTER|DT_CENTER);   ::SetTextColor(lpDrawItemStruct->hDC, crOldColor);}