Specifies the placement of the composition window relative to the pane. Composition here mean composing input characters into other characters by an input method.
The function set-composition-placement
tells the system where to place the composition window in pixel coordinates relative to the pane
pane
.
On systems where the composition text is displayed by the application (rather than by the system, when the composition callback is called with a plist), the placement coordinates are used to place the composition menu when it is raised.
x and y are the top left coordinates. If both width and height are supplied, they specify the dimensions of the composition window. If force is supplied with a true value, the coordinates are forced, overriding adjustments that the system may otherwise do.
x , y and, when supplied, width and height must all be positive integers.
set-composition-placement
does not raise the composition window. It merely tells the system where to place the composition window when it does appear.
CAPI User Guide and Reference Manual (Windows version) - 3 Aug 2017