dean@CHIVES.PSY.CMU.EDU.UUCP (01/27/87)
The problems we've had with the GPX and UIS are near endless. The leave behind characteristic was noticed right off. If you erase a window and then move another window across, you can see a history of what happened in that window. Our interactive graphics editor runs about 2-3 times slower on a GPX because of the way it is constantly updating the screen. These are all small and "work-around-able." The real problem we've had with the GPX is its lagging behind on the execution of UIS commands. I have a small piece of code which enables and disables screen blanking. During an experiment I turn the screen off to build the stimuli, but the GPX isn't to willing to let this work. Call Screen_Off() Call UIS$EXECUTE() Call UIS$SET_COLORS Call UISDC$READ_IMAGE Call UIS$ERASE Call Screen_On() This looks like it should work, right?. Wrong. The first problem is the call to UIS$SET_COLORS. Guess what it does for a side affect. Turns the screen back on. I didn't notice this in any documentation. The result is, I have to set_colors to all black, call execute, call read_image, call erase, and then restore the colors. But this still doesn't work like you might think. The screen still comes on with things on it. Why? The uis calls have not been executed yet. They all return asynchronously. I seemed to have missed this in the documnetation too. So how do you make sure all the uis calls you have made have executed. How about submitting a DOP and waiting for it to complete. Ok. Create a DOP packet and call UIS$EXECUTE_DOP_SYNCH; and your machine never returns. A little fooling around shows that UIS$QUEUE_DOP works fine. UIS$EXECUTE_DOP_ASYNCH works until the image runs down, or until you do a SYS$SYNCH on the IOSB. UIS$EXECUTE_DOP_SYNCH works but hangs immediately. I'm still wondering if the GPX was worth it. _________________________________________________________________ Randall W. Dean | | Research/Systems Programmer | None of the opinions stated | Psychology Department | above belong to anyone. | Carnegie Mellon University | | Pittsburgh, Pa 15213 |-------------------------------| (412) 268-3784 | Dean@A.Psy.Cmu.Edu | -----------------------------------------------------------------