At the beginning of each paint cycle, the control sends the NM_CUSTOMDRAW notification message, which specifies the CDDS_PREPAINT value in the dwDrawStage member of the accompanying NMCUSTOMDRAW structure. The value that your application returns to this first notification dictates how and when the control sends subsequent custom draw notifications for the rest of that paint cycle. The following table shows the flags that your application can return in response to the first notification.
Return value |
Effect |
| CDRF_DODEFAULT | The control draws itself. It does not send additional NM_CUSTOMDRAW messages for this paint cycle. This flag cannot be used with any other flag. |
| CDRF_NOTIFYITEDRAW | The control notifies the parent of any item-specific drawing operations. It sends NM_CUSTOMDRAW notification messages before and after it draws items. |
If your application returns CDRF_NOTIFYITEMDRAW to the initial prepaint custom draw notification, the control sends notifications for each item it draws during that paint cycle. These item-specific notifications have the CDDS_ITEMPREPAINT value in the dwDrawStage member of the accompanying NMCUSTOMDRAW structure. Your application can request that the control send another notification when it is done drawing the item by returning CDRF_NOTIFYPOSTPAINT to these item-specific notifications. Otherwise, your application can return CDRF_DODEFAULT, and the control will not notify the parent window until it starts to draw the next item.
If your application draws the item, it should return CDRF_SKIPDEFAULT. This enables the control to skip items that it need not draw, which conserves resources. Remember that returning this value means that the control will not draw any portion of the item, so your application must draw any item images.