Updating Tag Adornment Positions when Window Contents Shift

Hi Will,

Keep in mind that the AST nodes in Document.ParseData are not generally up-to-date and are based on an older document snapshot.  This is due to parsing occurring asynchronously after text edits.  I'm not sure which parser you are using to generate the parse data, but our LL(*) Parser Framework for instance has a ILLParseData.Snapshot property where we pass the ITextSnapshot used to generate the AST data.  That way we have the capability to translate text ranges so that the AST and snapshot ranges being considered are for the same snapshot.  

My guess is that in your scenario, you are comparing new snapshot ranges from the tagger to outdated offsets from the AST.

What you probably want to do is translate the AST offsets from their source snapshot to the current snapshot before comparing them in your tagger.  That would ensure everything is looking at the same snapshot and would do a proper comparison.

Thanks for the suggestion! I am using your LL(*) Parser Framework, so I was able to translate the AST offsets to the newer snapshot before comparing them exactly as you described.

Doing so fixed the misalignment when prepending new lines above the tagged and adorned scopes but not when scrolling the window. The text and adornments seem to move at different speeds. Do you have any additional guidance?

I got it working through trial and error. Initially in the DrawAdornmentCallback I was adding the adornment's Location property to the TextViewDrawContext's TextAreaBounds to generate the display Rect position. It turns out that I wanted to add the adornment's ViewLine.TextBounds instead.

I'm unclear what the adornment's Location represents/why it doesn't correspond exactly to its view line, but I'm happy to have my feature working. Thanks for the help!

Hi Will,

If you were only seeing the problem for horizontal scrolling, it could have been that your adornment X value wasn't accounting for the horizontal scroll state.  Check out our AdornmentsColorPreview sample's ColorPreviewAdornmentManager.OnDrawHighlightAdornment method.  There you can see how we calculate the X/Y properly when drawing the adornments.  That should give an example of best practice.

When you draw the adornment later, the drawing context is relative to the entire view, so you have to offset by the TextAreaBounds (text area relative to top/left of view), adornment location (relative to top/left of text area), and horizontal scroll amount.