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I am working on a project and I want to create and manage a window on every screen on the computer and update when / if screens are lost or gained. I hope some one can help…

I know that using General/[NSScreen screens] I can get an array of the screens at present and I imagine therefore that I can loop through the array something like this…

screens = General/[NSScreen screens];

for (i = 0; i < screens; i++ {

// get screen size screenRect = General/[[NScreen i] frame];

// Create window General/NSWindow *SCREENNAME = General/[[NSWindow alloc] initWithContentRect:screenRect styleMask:General/NSBorderlessWindowMask backing:General/NSBackingStoreBuffered defer:NO screen:General/[NSScreen mainScreen]];

[SCREENNAME setBackgroundColor:General/[NSColor blackColor]]; [SCREENNAME setAlphaValue:0.0]; [SCREENNAME setLevel:General/NSScreenSaverWindowLevel-2]; [SCREENNAME setReleasedWhenClosed:NO];


Assuming that were to work then I imagine that I would simply put that in a function which I call on awakeFromNib in my General/AppController (to create the windows) and then also there must be a notification some thing like screensDidChange: which I could override and implement some form of update to my windows to add or remove windows on screens where applicable.

Additionally windows also need to be manageable i.e. I would need some way to get them to perform a adjustment i.e. setting the color or adjusting the alpha value.

Now I know someone is going to say why don’t you use General/CGCaptureAllDisplays() but as far as I could work out there is no way to adjust this window i.e. alpha value. which I need as I want to be able to fade the screens from 0 to 1 or 0 to 0.75 using General/NSTimer to incrementally fade out/in.

I hope you guys can help I am very new to all this and whilst I have a comprehension of what I need to do I am very unsure as to how to actually implement this. Your help would be much appreciated!

If the point is purely to fade different screens in/out, why not use the function for that purpose, General/CGDisplayFade(…);? –GC

Thanks for that I was already aware of this soloution however in the past I have had an issue of switching from the fade to the General/CDCaptureAllDisplays() creating a short flash of the non black window. However this is gone now! Thanks.

I would like to ask though is there a way to get a pointer to the windows General/CGCaptureAllDisplays puts in as I actually need to set it to be semi transparent. I have spent alot of time looking to no avail.

The parameter doesn't need to be 0 or 1, it can be something in between. This leaves the display in a partially faded state. However if you plan to draw other windows on top at full brightness (like e.g. Dashboard) I'm not sure if that would work. There is a function General/CGShieldingWindowID() which seems to imply that there is a window associated with a captured display, and the function General/CGShieldingWindowLevel() would allow you to place a window above it. However, both of these functions come with warnings discouraging their use in apps, so it's unclear if it's a good approach. Sorry I don't know much about this - I have captured displays and faded them but only for full screen mode use and haven't tried what you seem to be attempting. Maybe someone more expert can step in here? --GC

Thanks for your help so far I hate to say it but I am quite new although I have a good grasp of what I am trying to do I have in fact tried the very same thing you suggested it seems that there is little to no functionality in the General/CDShieldingWindowID it all seems to cause a crash.

I have been looking for a long time which is why I came up with the idea of an array of screens which I could loop through as most users will only have 1 display for my application it would probably not be to taxing on the computer and most computers rarely if ever have more than 4 displays. My issue is I simply don’t have the knowledge or experience to create the idea I had in my original post by my self so if any one can indeed help me to create a loop through the displays which adds a window and sends messages to them and also detects when displays are connected or removed and appropriately adjust this then I would very much appreciate it. I will obviously continue working on this my self but if any one has any pointers or can help please do.

I have been working on this in a little mini app and this is what I have come up with it manages to create a window on every screen now all I need to do is work out how to loop thorugh them using a timer to fade I can see this would get quite resource intensive should the user have a larger number of displays as it will be calling a function every 0.1 seconds for every display 75 times in my case to fade from 0.0 to 0.75 in 0.1 fractions. I may try reducing this until the smoothness of the animation is just about to be comprimised.

Heres my work inprogress code for my General/AppController…


WOOP! I did it all by my self pretty much!

I would appreciate some feedback on how well coded it is.

#import “General/AppController.h”

@implementation General/AppController