WM_IME_COMPOSITION Message

When the IME generates the WM_IME_COMPOSITION message, it specifies the lParam as GCS bits. The GCS bits means the available member of the COMPOSITIONSTRING structure. Even if the IME does not update and the member is available now, the IME can set the GCS bit.

Service Definition for IME

When IME generates the WM_IME_COMPOSITION message, it may change the string, the attribute, and the clause information at once. The IME can use the follow definitions.

GCS_COMP

GCS_COMPREAD

GCS_RESULT

GCS_RESULTREAD