Automate annotation locations

Question

Hi,
I've been trying out the Annotations in LabVIEW 8.5 and they work well except for a few issues I tend to be having. I have a grpah that needs 5 annotations in them, but they may be anywhere in the graph. What I am trying to avoid is overlap between the annotation labels together. Here are some examples of what I am talking about. The first graph shows a bunch of annotations all overlaping. I zoom in on the graph and they reorder properly and look clean, but I can not allow the graph to always just zoom in on the annotations, I need the graph to be the full view. So the last graph shows how I would like the annotations to automatically orient themselves with each other to get a best fit around the cursor points without overlapping their own space.
Graph As Is
Graph zoomed
Graph moved
Is this something that NI can look into providing or is there another alternative that I can work on in the background? How should I proceed in accomplishing this?
I have used other graphs through active X that can do a better job of annotations, but have a memory leak. If I can find a way to get the NI graphs to mimic these below, I much rather would.
Graph to Mimic
Thanks,
--Kevin
Kevin Shirey
PVI Systems Inc.
Certified LabVIEW Developer

Answer 1

So I’ve gotten the Annotations to a ‘usable’ solution for our product. I ended up adding a lot of code to make the usability easier for the user and as fully featured as I could. I submitted a product suggestion form as well. I also documented it all in a word doc for you so look for the attachment with more graphs. I also have some example code I can provide for what I have done.
Improvements I’ve been able to account for:
Y offset to annotation label based on crosshair size
The first hurdle was to show the annotation in the correct position on the cursor. I had to first offset the annotation label by a factor based on the size of the crosshairs (I couldn’t have the annotation drawn right on top of the crosshair as default). So based on the Y scale factor of the plot, I always offset the annotation label in Y +/- an amount to offset it from the crosshair.
Label in + or – Dimension from the crosshair
Another issue is that the annotation label can be off screen based on the tight factors of the plot. If the data reachs the top of the graph, the annotation is lost because it is off the screen in the plot. So, based on the location of the point and the maxima of the Y scale markers, I can decide to offset the annotation label in the negative direction in respect to the crosshair. The graphs below help illustrate that.
Event Structure Code to automate replotting the visible Annotations
    Change Cursor color when it moves
    I allow the user to move the cursor so they can easily view the Y value. As you see in the graphs above, when a cursor is moved, I change it to black to note that the user changed its position and it is not the point chosen by the software.
    Redraw annotations when it moves
    When the cursor moves, I have to call my code to update the annotation label. This involves changing the annotation data/location, offset in terms of Y and the +/- flip.
    Zooming on a graph changes visible annotation labels
    When a user changes the scale factor by zooming in on the graph, the visible annotations should change. We may be able to view more or less Annotations so I chose to redraw them. Basically, the annotations are always setup when the data is drawn in the plot, but I make them visible or not.
Showing Annotations based on X, then Y
The difficult part of annotations was altering the location/offset for the label depending on the surrounding annotations. I first prioritize annotations based on the strongest peak first. The graph shows the annotations that fit within X. Then if it doesn't fit within X, show it in Y.
Other features out of my control that would make this better:
Allowable font and size for Annotation Labels.
Automatic visibility and location of annotation labels that can smartly move them slightly to account for crosshairs, surrounding annotations, using a line (not arrow) to point to the annotation location as seen in the graph below which is not from LabVIEW.
Auto redraw the annotations when changes made. I have to defer panel updates to force a redraw of the annoation labels because I get intermittent refesh issues with the labels. Note the 154.1, the 1 gets cut off. By clicking on the label, it gets refreshed, or dragging the window off then on screen.
Kevin Shirey
PVI Systems Inc.
Certified LabVIEW Developer
Attachments:
annotations.doc ‏744 KB