Retrieving Graphic-Object Attributes and Selecting New Graphic Objects
An application can retrieve the attributes for a pen, brush, palette, font, or
bitmap by calling the
GetCurrentObject and
GetObject functions. The
GetCurrentObject function returns a handle identifying the object currently selected into the
device context; the
GetObject function returns a structure that describes the object's attributes.
The following example shows how an application can retrieve the current brush
attributes and use the retrieved data to determine whether it is necessary to
select a new brush.
HDC hdc; /* display DC handle */
HBRUSH hbrushNew, hbrushOld; /* brush handles */
HBRUSH hbrush; /* brush handle */
LOGBRUSH lb; /* logical-brush structure */
/*
* Retrieve a handle identifying the current brush.
*/
hbrush = GetCurrentObject(hdc, OBJ_BRUSH);
/*
* Retrieve a LOGBRUSH structure that contains the
* current brush attributes.
*/
GetObject(hbrush, sizeof(LOGBRUSH), &lb);
/*
* If the current brush is not a solid-black brush,
* replace it with the solid-black stock brush.
*/
if ((lb.lbStyle != BS_SOLID)
|| (lb.lbColor != 0x000000)) {
hbrushNew = GetStockObject(BLACK_BRUSH);
hbrushOld = SelectObject(hdc, hbrushNew);
}
/* Perform painting operations with the white brush. */
/*
* After completing the last painting operation
* with the new brush, the application should
* select the original brush back into the
* device context and delete the new brush.
* In this example, hbrushNew contains a handle
* to a stock object. It is not necessary (but it
* is not harmful) to call DeleteObject on a stock
* object. If hbrushNew contained a handle to a brush
* created by a function such as CreateBrushIndirect,
* it would be necessary to call DeleteObject.
*/
SelectObject(hdc, hbrushOld);
DeleteObject(hbrushNew);
Note that the application saved the original brush handle when calling the
SelectObject function the first time. This handle is saved so that the original brush can
be selected back into the device context after the last painting operation has
been completed with the new brush. After the original brush is selected back
into the device context, the new brush is deleted, freeing memory in the GDI
heap.
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