This structure contains mouse hit-test constants. The following enumerators are defined within the scope of the structure hit_test.
| Enumerator | Location |
| Border | The border of a window that does not contain sizing borders. |
| bottom | The lower border of the window. |
| bottom_left | The lower-left corner within the border of the window. |
| bottom_right | The lower-right corner within the border of the window. |
| Buttonmaximize | The maximimize button of the window. |
| Buttonminimize | The minimimize button of the window. |
| caption | The title bar of the window. |
| client | The client area of the window. |
| close | On the window's close button. |
| error | On the desktop background or on the dividing line between windows. |
| help | The help button attached to the window. |
| left | The left border of the window. |
| maximize | The maximize button of the window. |
| menu | The window's menu bar. |
| Nowhere | On the desktop background or on the dividing line between windows. |
| Reduce | The minimize box of the window. |
| right | The right border of the window. |
| horizontal_scroll | The horizontal scroll bar attached to the window. |
| vertical_scroll | The vertical scroll bar attached to the window. |
| size | The sizing box of the window. |
| system_menu | The system menu of the window. |
| top | The upper border of the window. |
| top_left | The upper-left corner of the window. |
| top_right | The upper-right corner of the window. |
| transparent | In a window that is currently covered by another window. |
The enumerator hit_test::error is similar to hit_test::Nowhere, except that the default window procedure responds by beeping.
The hit-test constants are used to determine the location of the cursor when it has been moved or when a mouse button is pressed or released. The message message::nonclient_hit_test and the class hook_mouse_information refer to this enumeration.