fixes history loading slowly due to context switches

frontend/src/components/SvgGraph.vue

@@ -198,6 +198,8 @@ const show_data_at_time = computed(() => {
     }
 });
 
+const should_fade = ref(false);
+
 provide<GraphData>(GRAPH_DATA, {
     border_top: border_top,
     min_x: min_x,
@@ -216,6 +218,7 @@ provide<GraphData>(GRAPH_DATA, {
     legend_y_stride: legend_y_stride,
     legend_width: legend_width_output,
     cursor_time: show_data_at_time,
+    should_fade: (value) => (should_fade.value = value),
 });
 </script>
 
@@ -286,7 +289,9 @@ provide<GraphData>(GRAPH_DATA, {
                     ></TimeText>
                 </template>
             </g>
-            <slot></slot>
+            <g :class="`${should_fade ? 'fade' : ''}`">
+                <slot></slot>
+            </g>
             <g class="cursor_tick" v-if="mouse_t && cursor">
                 <rect
                     :x="x_map(mouse_t) - 100"