Step 8: PE_ENDDATA Message
The PE_ENDDATA message informs a target window that input for the target has
ceased. The message's
lParam points to a
TARGET structure, the
dwData member of which identifies the
HRC or
HPENDATA created in step 6. If recognizing
input through an
HRC object, the application should let
DefWindowProc handle this message. However,
DefWindowProc will destroy an
HPENDATA object when processing PE_ENDDATA. To preserve the
HPENDATA, the application has two choices:
- Trap the message, preventing it from reaching DefWindowProc. In this case, the HPENDATA object outlives the input session. Note that an HPENDATA object occupies memory in the system heap. When finished, the application
must remove the object by calling DestroyPenData to avoid wasting resources.
- Alternatively, copy the HPENDATA object with DuplicatePenData before letting the PE_ENDDATA message fall through to DefWindowProc. However, this approach has no advantage over the preceding method, merely
trading the original object for its clone. Again, the application is responsible
for destroying the new HPENDATA object.
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