In this lesson, we examine the Component Overlay system in Perspective.

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[00:00] Bindings in Perspective features an overlay system. This overlay system lets you know when there is a problem with one of the bindings. So, here we see I have a Label, which has a little red border and a little exclamation mark. That's part of the overlay system. So if I select the component, we can see that the text property has a little red background. If I hover over this little icon, it tells me that there's a configuration error. So, whenever there's a problem with one of these bindings here, we'll simply place an overlay on the component. Now, if I were to select that component and take a look at the binding here, I'm using a tag binding to Tower One/PH, and we can see that it's still giving me an error configuration. So, there's something wrong with this tag. Now, of course if I look in the Tag Browser, we can see under Tower 1 that yeah, that PH tag also has a configuration error. So, really the problem in this case is with the tag, but the overlay system is letting me know. So, to fix this, I don't actually have to change the binding here, I just need to address my tag. So, I can close this window here, and if I double click on that PH tag, I intentionally changed the OPC item path to have an extra character at the end here, which, if we were to delete, I can hit OK, and you'll see everything starting to run again, and I no longer have the overlay on the component. Now, if we were to look at this in a larger scale, say I wanted to see what happens when I lose connection with a device or basically get a bunch of overlays at the same time. So, I'm going to head over, and I'm actually going to disable my OPC UA server. And you'll see in just a moment here, because again, all of these tags have unknown quality, they're using the last known value, my components also get some overlays. So, we'll go ahead and we'll turn that back on. And in just a moment, there we are, we're getting values so we remove the overlays. Now, it's important you understand that this overlay system doesn't just work with Tag Bindings, it's any binding. So, for example, if I were to go to this LED Display here, and if I were to replace the binding on the value property, so, instead of using a Tag Binding, I could instead use a Expression Binding. So if this expression came up with some sort of error, such as not having an expression at all, I can hit OK here, and again you'll see the overlay system kick in to effect. So, once again, if there's every any problems with any bindings, these overlays will let your users know right away.

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