Fix Cursor Grab while panning (#4957)

Co-authored-by: John Hill <john.c.hill@nasa.gov>

src/plugins/plot/MctPlot.vue

@@ -76,6 +76,9 @@
                 <div
                     ref="chartContainer"
                     class="gl-plot-chart-wrapper"
+                    :class="[
+                        { 'alt-pressed': altPressed },
+                    ]"
                 >
                     <mct-chart
                         :rectangles="rectangles"
@@ -230,6 +233,7 @@ export default {
     },
     data() {
         return {
+            altPressed: false,
             highlights: [],
             lockHighlightPoint: false,
             tickWidth: 0,
@@ -268,6 +272,8 @@ export default {
         }
     },
     mounted() {
+        document.addEventListener('keydown', this.handleKeyDown);
+        document.addEventListener('keyup', this.handleKeyUp);
         eventHelpers.extend(this);
         this.updateRealTime = this.updateRealTime.bind(this);
         this.updateDisplayBounds = this.updateDisplayBounds.bind(this);
@@ -299,9 +305,21 @@ export default {
 
     },
     beforeDestroy() {
+        document.removeEventListener('keydown', this.handleKeyDown);
+        document.removeEventListener('keyup', this.handleKeyUp);
         this.destroy();
     },
     methods: {
+        handleKeyDown(event) {
+            if (event.key === 'Alt') {
+                this.altPressed = true;
+            }
+        },
+        handleKeyUp(event) {
+            if (event.key === 'Alt') {
+                this.altPressed = false;
+            }
+        },
         setTimeContext() {
             this.stopFollowingTimeContext();
 

src/styles/_legacy-plots.scss

@@ -160,6 +160,10 @@ mct-plot {
             bottom: 0;
             left: 0;
         }
+        .alt-pressed {
+            // When alt is being pressed and user is hovering over the plot, set the cursor
+            @include cursorGrab();
+        }
 
         .gl-plot-axis-area.gl-plot-x {
             top: auto;