get_update_rectangle


bool get_update_rectangle(handle window,
                          irectangle* update,
                          booleErase)

This function obtains the rectangle bounding the update region of a window.

Parameters

handle window

The handle of the window whose update rectangle is being queried.

irectangle* update

A pointer to a rectangle that is updated to hold the bounding rectangle of the update region. If this parameter is null, no update rectangle is returned; however, an indication of whether the update region is non-empty is returned. This may be useful for determining whether a paint message was generated as a result of a non-empty update region.

bool erase

This parameter determines if the background of the update region is to be erased. When this parameter is true and the update region is non-empty, an erase background message is sent to the window.

Return

bool

true The update region is non-empty.
false The update region is empty.

Notes

If the window has the style class_style::own_device_context and the mapping mode is not unit::pixel, the bounding rectangle is expressed in logical coordinates; otherwise, it is expressed in client coordinates.

If there is no update region, an empty rectangle results (all coordinates set to zero).

The update rectangle obtained via the function begin_paint is the same as the update rectangle returned by this function. Because begin_paint validates the update region, a call to this function immediately following a call to begin_paint returns an empty update rectangle.