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These operations allow you to read some of the events that are generated by the Presentation Manager and put in the message queue of a graphics-device window.
operation+: os2-graphics-device read-button
This operation waits for the user to push a mouse button inside the client area of the graphics-device window. It then returns four values (see section Continuations) which are: the button number; the x and y coordinates of the mouse pointer at the time the button was pressed, in pels (pixels) relative to the lower left hand corner of the client area; and the graphics device that the mouse pointer was over at the time the button was pressed.
Note that this operation only works when button events are selected (which is the default).
operation+: os2-graphics-device select-user-events mask
This operation sets the event-selection mask for the graphics device to
mask. The event-selection mask is an exact non-negative integer
that specifies which types of incoming events are to be saved in the
user-event queue for later retrieval by the read-user-event
operation. The mask is specified by setting the bits corresponding to
the event types that you are interested in, as follows:
Number Mask Description ------ ----- ----------- 0 #x001 Button press/release 1 #x002 Close (close the window) [WM_CLOSE] 2 #x004 Focus change [WM_SETFOCUS] 3 #x008 Key press/release [WM_CHAR] 4 #x010 Paint [WM_PAINT] 5 #x020 Size change [WM_SIZE] 6 #x040 Visibility change [WM_SHOW] 7 #x080 Command [WM_COMMAND] 8 #x100 Help [WM_HELP] 9 #x200 Mouse-move [WM_MOUSEMOVE]
Note that this operation does not affect any events that are already in the user-event queue. Changing the mask only affects what events will be added to the queue in the future.
operation+: os2-graphics-device read-user-event
This operation returns the next user event available from the user-event queue. If there are no events in the queue, the operation waits for an event to arrive before returning.
An event is a vector whose first element is the event-type number, whose second element is the graphics device that the event refers to, and whose remaining elements provide information about the event. Here is a table of the possible event types and their vector layout:
#(0 device number type x y flags)
0 is usually the left mouse button, 1 is usually
the right button, etc. Type specifies what occurred: 0
means the button was pressed, 1 means the button was released,
2 means the button was clicked, and 3 means the button was
double clicked. X and y are the position of the mouse
pointer at the time of the event, in units of pels (pixels) measured
from the lower left corner of the client area of the associated window.
Finally, flags specifies what shift keys were pressed at the time
of the button event; it is a mask word created by combining zero or more
of the following flags: #x08 means the shift key was pressed,
#x10 means the control key was pressed, and #x20 means the
alt key was pressed.
#(1 device)
#(2 device gained?)
#t, the keyboard focus is
being gained, and if gained? is #f, it is being lost.
#(3 device code flags repeat)
#(4 device xl xh yl yh)
#(5 device width height)
#(6 device shown?)
#f, the window is hidden,
and if it is #t, the window is shown.
#(7 device source mouse?)
#(8 device source mouse?)
7 indicates a command from a `WM_COMMAND' message, while
8 is a command from a `WM_HELP' message.
#(9 device x y hit-test flags)
operation+: os2-graphics-device discard-events
This operation discards any events that are in the user-event queue. This is sometimes useful when you want to prompt the user for some input and don't want to consider any previous input.
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