Started work on Distance Tool (#3609)

* Started work on Distance Tool

* Started work on Distance Tool

* Started work on Distance Tool

* Continued Work on Distance Toool

* Altered Key press logic for distance tool

* Implemented a snap feature with 'alt-d' key press

* Added Distance Table

* Added Data Label & made UI clearer

* Added the ability to create multiple lines on the viewer

* Added the Distance Tool to the Imviz Docs

* Incereased Visibility of data label

* Added Changelog Entry

* Addressed Comments and changed how the viewer is cleared

 Pleas ente the commit message for
your changes. Lines starting

* Fixed label offset distance

* Fixed Cubviz Distande Label

* Fixed Error in Clear Table for CubeViz

* Security Vulnerability Fix

* Correct test failures

---------

Co-authored-by: Jason Virts <[email protected]>
Co-authored-by: Jason Virts <[email protected]>
Co-authored-by: Jason Virts <[email protected]>

Author: 4 people

CHANGES.rst

@@ -4,6 +4,9 @@
 New Features
 ------------
 
+- The Markers plugin now includes a Distance Tool to interactively measure and log pixel, on-sky, and axis-separated (dx, dy) 
+  distances between points in any viewer. [#3609]
+
 - The Plot Options plugin now highlights the tab for the active (top-most) data layer
   in the selected viewer. [#3514]
 

docs/imviz/plugins.rst

@@ -211,6 +211,35 @@ In Imviz, the table also exposes columns labeled "pixel:unreliable", "world:unre
 the bounds of the reference image's WCS (noted in the mouseover display by the information showing
 as grayed).
 
+.. _imviz_distance-tool:
+
+Distance Tool
+-------------
+
+The Markers plugin also includes a tool for measuring the distance and position angle between
+two points in a viewer. This functionality is available whenever the Markers plugin is open.
+
+
+1. Mouse over the desired start point in a viewer and press the ``d`` key. A ``...`` indicator
+   will appear in the :guilabel:`Last Measured Distance` field at the bottom of the plugin,
+   showing that the first point is set.
+2. Mouse over the desired end point and press the ``d`` key again.
+
+This will draw a line between the two points. A label showing the distance will appear,
+rotated to be parallel with the line, and offset to prevent intersecting the line.
+
+A new table, :guilabel:`Measurements`, will also appear below the main markers table. This
+table logs the start and end coordinates (both pixel and world, if available), the on-sky
+separation, the pixel distance, and the position angle for each measurement.
+
+**Additional Features:**
+
+* **Snapping**: To measure the distance from or to an existing marker, hold down the ``Alt`` key
+  (or ``Option`` on Mac) when you press ``d``. The tool will "snap" to the nearest marker
+  already in the main table.
+* **Clearing**: Pressing the ``r`` key will clear all markers from the main table *and* all
+  distance lines from the viewers.
+
 From the API
 ------------