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Mac Forum / Programming / Mac Programming / May 2007How to GetNextEvent in XCode
Thanks, Reinder, this helps. >A:> I need to write a reader for a barcode scanner, >B:> so I need access to all that comes on the keyboard. > I do not see how B follows logically from A. Let me explain more of the operation. I set up a barcode scanning system for a school library on Mac OS9. It scans into FileMaker files. Normally this requires a person to be present to start up the system, open FileMaker, create a new record and position the cursor into the field for the barcode. Then for the next scan, the operator would create a new record and put the cursor into the field. I automated the system for completely unattended operation. The teachers just scan the bacodes and nobody pays any attention to the monitor display. The barcode scanner has pre-scan and post-scan ability. Pre-scan is currently set to F5, Cmd-1. F5 is grabbed by KeyQuencer and causes FileMaker to become the front most application. Cmd-1 runs a script in FileMaker that forces the cursor into the correct file, layout and field, and creates a new record. Basically it is the F5 operation I need to reproduce because there is no version of KeyQuencer for OSX. Also, the barcode producer has no plans to make an OSX version of the pre-scan/post-scan software. So I need to write code that will grab the event stream watch for a barcode then bring FileMaker to the front and type the Cmd-1. What I read about Carbon and Cocoa is that only events that occur in an apps own windows are sent to the app. Ski > Thanks, Reinder, this helps. > >A:> I need to write a reader for a barcode scanner, [quoted text clipped - 31 lines] > > Ski If you want to set up a single global hot-key like what you seem to be describing, it borders on trivial. Mostly depending on whose definition of trivial you use. Look for a function named RegisterEventHotKey. Then create an event handler for kEventHotKeyPressedSubtype. There may even be a way to do it just by configuring something the right way in the keyboard system preferences. >> Thanks, Reinder, this helps. >> >A:> I need to write a reader for a barcode scanner, [quoted text clipped - 42 lines] > There may even be a way to do it just by configuring something the > right way in the keyboard system preferences. It is not a hot key I need. Teachers scanning books never come near the keyboard or the monitor. It all has to happen automatically including the fact that FileMaker may not even be the front app. MacOSX was specifically hampered for security by sending events to an app only if the event occurs in one of the apps windows. I think Reinder gave me the right clue yesterday. Mac OSX10.4 came forward with EventTaps which apparently recognized the problem of OSX in overprotecting memory from any app by allowing it to only get events originating in its own windows. EventTaps are documented here: <http://developer.apple.com/documentation/Carbon/Reference/QuartzEventServicesRef /index.html> > I think Reinder gave me the right clue yesterday. > Mac OSX10.4 came forward with EventTaps which apparently recognized the [quoted text clipped - 3 lines] > <http://developer.apple.com/documentation/Carbon/Reference/QuartzEventServices > Ref/index.html> The modern way for apps to communicate with each other is to send them an appleEvent. look into osascript, Script Editor, and AESend(). To support the disabled, a user can even turn on U.I. scripting, which allows programs to send each other click on controls, on menu items, and arbitrary mouse clicks and keydowns. The security in OS X is there for a reason. Professional quality programs on Macintosh should not require the user to turn off security for the entire machine. >> I think Reinder gave me the right clue yesterday. >> Mac OSX10.4 came forward with EventTaps which apparently recognized [quoted text clipped - 14 lines] > programs on Macintosh should not require the user to turn off security > for the entire machine. Thanks for the suggestion but it does not address my problem. (I have made apps AE scriptable) I have to have an app that watches EVERY keyboard character and detects a barcode scan, switch to FileMaker and send the barcode on to Filemaker. I can use AE cause Filemaker to come to the front but that doesn't solve the problem of the OS only sending the KB strokes to the app that has its window in front. Ski > >> I think Reinder gave me the right clue yesterday. > >> Mac OSX10.4 came forward with EventTaps which apparently recognized [quoted text clipped - 22 lines] > but that doesn't solve the problem of the OS only sending the KB strokes > to the app that has its window in front. Use a faceless background task to open the scanner as a USB device, have it send an appleEvent to Filemaker to create an appropriate record. Filemaker need not come to the front. > [snip] >> > In article <Xns993C60F12EA5Cskiacrobytes@69.28.173.184>, > > Use a faceless background task to open the scanner as a USB device, > have it send an appleEvent to Filemaker to create an appropriate > record. Filemaker need not come to the front. Thanks for this advise. May be the best idea. Ski > > [snip] > [quoted text clipped - 5 lines] > > Thanks for this advise. May be the best idea. I personally, inspired by HID Explorer, http://developer.apple.com/samplecode/HID_Explorer/ , wrote a program that a Dance Dance Revolution style USB Dancepad, opens it as a USB device, decodes it, and sends AppleEvents to Google Earth, http://www.google.com/mac.html , so you can run in place on the dance pad and stride over the earth like a giant. It isn't faceless background task, since it draws a "keycaps" style animation of the state of the dancepad, just an ordinary app, bit it works even if it, and/or Google Earth, are not the front app. I also used the open source barcode scanner software, http://www.bruji.com/cocoa/ , put a Firewire DV video camera on a tripod, and used it to scan a few dozen DVDs. This software also works with the iSight camera built in to recent Macs. > Look for a function named RegisterEventHotKey. Then create an event > handler for kEventHotKeyPressedSubtype. I'd like to intercept the Spotlight hot-key (e.g. <cmd>+<space>) while in my application so that Spotlight doesn't put up it's search "pop-up" and I can use the sequence as a command. I thought that the above might be a good starting point toward the solution, but the docs don't seem to address Spotlight. Is there a standard way of suppressing Spotlight. /nt  SignatureDelete this to reply directly. > > Look for a function named RegisterEventHotKey. Then create an event > > handler for kEventHotKeyPressedSubtype. [quoted text clipped - 8 lines] > > /nt Command-space is also assigned to "Select previous input source", so if you disable Spotlight somehow, it will be used by that. That being said, the "Keyboard Shortcuts" panel in the Keyboard & Mouse preference pane handles this sort of assignment, allowing pretty much arbitrary uses of them, so the user may have command-space assigned to something that they consider even more important than either Spotlight, input sources, or your application. > That being said, the "Keyboard Shortcuts" panel in the Keyboard & Mouse > preference pane handles this sort of assignment, allowing pretty much > arbitrary uses of them, so the user may have command-space assigned to > something that they consider even more important than either Spotlight, > input sources, or your application. Good point, and it makes me realize I didn't ask the right question. What I'm really interested in is making sure the keycode for <cmd>+<space> gets to my application wether it's assigned to some other system function or not. I would have thought that having a keyDown: method defined in my first responder view would have done it, but that doesn't seem to be the case. Ideally, the solution would let me intercept all key-codes and let me consume the ones I'm interested in, and pass the rest to the system. So for example, I'd act on <cmd>+<space> but allow other keys like Volume+/- or Brightness*/- pass to the system. Thanks for the reply. /nt SignatureDelete this to reply. A) > The barcode scanner has pre-scan and post-scan ability. > Pre-scan is currently set to F5, Cmd-1. [quoted text clipped - 5 lines] > version of KeyQuencer for OSX. Also, the barcode producer has no plans to > make an OSX version of the pre-scan/post-scan software. B) > So I need to write code that will grab the event stream watch for a > barcode then bring FileMaker to the front and type the Cmd-1. Again, I do not see how B follows from A. Apparently, under Mac OS 9, the scanner has custom software that: 1) detects that a barcode is scanned 2) executes some user pre-scan code 3) emulates a keyboard to emulate a keyboard that types the barcode 4) executes some user post-scan code I also guess that the scanner claims to be a USB keyboard. So, under Mac OS X, without any custom driver for the device, the scanner types barcodes into the frontmost application. You seem focussed on step 2 only, but if the above is true, you will have to write code for steps 1 through 4. If you do not, there is no way to fire step 2 at the right time or to have step 3 wait until step 2 has finished. If so, your best route probably is a USB driver for the specific vendor ID/product ID. You might be able to get away with a user-level one, but I doubt it. Googling on this gave me the following links that you might want to be aware of: <http://lists.apple.com/archives/usb/2004/Mar/msg00062.html> shows that you are not the first trying this. <http://www.easybarcodetech.com/ebr.html> shows a reader that does what you want. It seems that $256/unit solves your problem (just buy new scanners) <http://www.delicious-monster.com/> also sells a scanner that may or may not be usable for you. > What I read about Carbon and Cocoa is that only events that occur in an > apps own windows are sent to the app. That is not much different from Mac OS 9, except that Mac OS 9 made it, in some sense, easier to hack around this (Mac OS X probably makes it easier to do so without disrupting system stability) Reinder |
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