I'm trying to do some screen capturing on Mac OS using the standard CGDisplayStreamCreateWithDispatchQueue API, however I keep getting a NULL stream Ref when I call the API, and there is apparently no error information so I can't figure ut why it is failing.
I have tried code from these two sources (with minor tweaks when needed):
Capture screen with CGDisplayStream
https://github.com/diederickh/screen_capture/blob/master/src/test/test_mac_api_research.m
I have also tried CGDisplayStreamCreate(), and using a variety of resolutions and pixel formats. I have also confirmed CGGetActiveDisplayList is returning back one CGDirectDisplayID which I am passing to the API call.
Can anyone suggest what might be causing this silent failure?
Thanks.
I figured out the problem. It appears either I had accidentally clicked 'No' to the screen sharing permissions, or it hadn't come up. In any case, using the command in this question I was able to reset things and now it works.
How to trigger screen recording permission system modal dialog on macOS Catalina
Related
System specs: mac OS Monterrey V12.5, Apple M1 chip 2020
I am making an application which will take a screenshot of a video, and take the timestamp of the current point in this video, after which both the timestamp and screenshot will be send to a numbers file (mac OS excel like program).
I could not find an application to do this and I tried to get it working using python as shown here but was unable to. Now because I am on Mac I have decided to use Automator instead. I am currently on the screenshot part and Automator has a build in screenshot functionality.
Unfortunately, this screenshot does not detect browser or application windows, it will only take a screenshot of my background.
I have no idea why this is but I suspect it might have to do with permissions related to the M1 chip.
I tried different monitors and simplyfying the automation to just taking a screenshot, but so far nothing has helped, I could not find others online who had a similar problem.
If there is any information missing from this post I will be happy to provide it.
Edit: It seems to be some kind of permission issue, automator CAN take screenshots within Safari, now I just need to find a way to do so in firefox.
I have solved the issue, it turns out that the M1 chip has a special permission for screen recording, adding my Automator application to this permission list will allow it to take screenshots of all windows.
I'm using opengl es 3.0 API with the android studio ndk to create apps.
But I've encountered a very huge problem. I've created a demo app, all it does it change the background color of the screen from white to black and vice versa, every frame. And so when I go to minimize this app, I still see it rendering the background, mostly at the edges of the screen, and not in full color but still very strongly apparent. And it doesn't go away when I close the app, when I restart the device, or when I run "kill apps" on it. Only a factory data reset fixes the issue, so it's not easy for me to debug this.
This is the relevant code that I'm using for when the app is minimized and receives the APP_CMD_TERMINATE event:
eglMakeCurrent(engine->display,EGL_NO_SURFACE,EGL_NO_SURFACE,EGL_NO_CONTEXT);
eglDestroySurface(engine->display,engine->surface);
engine->display = EGL_NO_DISPLAY;
engine->surface = EGL_NO_SURFACE;
I've error checked that eglDestroySurface() is successful.
And I've put debugging messages in to make sure that the main draw loop is NOT executing when the app is minimized. But the problem persists and I don't know what to do about it. Thanks for any help.
UPDATE: well, no one has responded, and I still don't know what to do. Could it be related to threads?
UPDATE: Still can't determine what it is, but for some reason it's messing with the System UI. Willing to upload my entire source code somewhere if someone would be willing to go through this with me, as I'd really like to be able to continue working on my game engine.
Is it the "Strict Mode" developer option on the device settings, perhaps?
That one flashes the screen if an app is blocking.
It would explain why a factory reset changes behaviour.
The answer is not a solution here. The above comment by the user columbo was correct.
I've demoed switching from black to white at high framerates on 3 different android devices, and also my Linux Desktop, all via the openGL api, and it has exhibited this issue on all the devices. So what he said must be correct: this is a problem with LCD monitor technology itself. Interestingly, doing completely random colors does not cause this problem.
I am developing a macOS app which takes control of the cursor. I am using a CGEvent Tap and I am adding some arithmetic to the CGEvents in order to offset the final mouse position. Although the app is in principle working as expected, in some cases - more specifically: when running the app with certain popular illustration software and using a stylus pen - the app is producing some flickering 'ghost' positions for the mouse at its original location. The good thing is, this problem can be resolved when running the app while being logged in as root user. I have read quite some SO posts but this particular post addresses the issue best:
https://stackoverflow.com/a/9899901/5066660
As described in this post the issue is probably:
Unfortunately, the CGEventTapCreate() doc says:
Only processes running as the root user may locate an event tap at the point where HID events enter the window server; for other users, this function returns NULL.
Well the function is definitely not returning null because the tap is in effect. Also I tried all possible combinations of arguments for that function, but they all act the same. Further down in that post it is proposed to tackle the problem as follows:
Perhaps you can spin this functionality off into a separate process that has super-user permissions, leaving the rest of your app in normal user mode? I believe there's also a way to request root permissions for just a specific action taken by your program.
Now if this is a possible solution I would love to implement it! So my question is: how? I've stumbled upon running scripts with elevated permissions, but not just CoreGraphics code as for example an CGEventTap. Is this possible? Could anybody give me an example of how this could be accomplished, or any other solution to the problem?
All help is welcome, thank you very very much.
From Apple documentation:
Event taps receive key up and key down events if one of the following conditions is true:
- The current process is running as the root user.
- Access for assistive devices is enabled. In OS X v10.4, you can enable this feature using System Preferences, Universal Access panel, Keyboard view.
So giving the the application Accessibility rights solved it for me (no need to run as admin). This can be achieved System Preferences -> Security & Privacy -> Accessibility and add you program there.
I am developing a simple application in Cocoa, and I want to detect whether any application is running in full screen mode. Is this possible?
Through runningApplications API, I can get various informations but there is no specific property related to full screen mode. Does any one know how to detect it? Is there any carbon event or API for this?
I ran into this in the spring and spent forever trying to get it to work. I ended up packaging my code up into a little GitHub project, but I completely forgot to share it here.
https://github.com/shinypb/FullScreenDetector
Hope this is useful for someone.
Anyways after trying out so many options and digging into the NSWorkspace i have found way through which we can achieve this their is notification
"NSWorkspaceActiveSpaceDidChangeNotification"
Apple doc says "Posted when a Spaces change has occurred." so by using we can register for it. along with this we need to use the NSWindow's property "isOnActiveSpace" , so by this we can detect when application enters full screen mode and exits from it.
You want to key-value observe -[NSApplication currentSystemPresentationOptions]. When the active app is in full-screen mode, that property will include NSApplicationPresentationFullScreen.
I have an app that I have been developing that can display sensitive user data.
When the user backgrounds the app, the OS appears to take a screenshot of the app as it was running, and displays it so when the user returns, their state is restored.
I am trying to prevent the user's information from being seen in this screenshot.
My initial idea was to display a Popup of my splash screen image, but it does not seem to render it in ApplicationDeactivated. Is there any other way you might accomplish this?
I am not sure you are analyzing this correctly. I don't see how the OS could take a screenshot of an app and use that to restore state. Also, if it was true that the OS did that, Tomb Stoning wouldn't be such a big issue in the requirements for an app in the submission process. A dev needs to handle grabbing and saving state on exit and reloading it on start-up again.
If you didn't code this tomb stoning, are you using a frameowrk that has built in support for this? You could disable the tombstoning so certain pieces of information are not stored, and in fact if this data is that sensitive you should make sure it isn't saved. But, if you save it make sure you encrypt it so nothing else could examine the saved state. Although, that shouldn't be possible on Win Phone as the OS is supposed to enforce the boundries between apps.
Received a response from Microsoft which indicates that this is not possible in the Mango SDK; it may be added into future releases of the platform.