Fix graph crash on reload, even out depth sizes

Frontend/src/Components/GraphPane.jsx

@@ -20,8 +20,11 @@ const LabelZoom = 0.7; // below this, only hovered labels are drawn
 const ClickSlop = 4; // pixels a click may wander and still count as a click
 // Directories by depth, like the headings: h1 Purple, h2 Blue, ...
 const DepthRoles = ["Purple", "Blue", "Green", "Yellow", "Orange", "Red"];
-const ShrinkPerDepth = 0.8; // with ShrinkByDepth, each level's directory dots are this much smaller
-const SmallestDirectory = 3; // ...but never smaller than a file's dot
+// With ShrinkByDepth, directory dots shrink in even steps from their usual
+// size to a file dot's size (a file with one link) at this depth (the red
+// ones), and stay that size below it.
+const ShrinkDepth = 5;
+const FileDotRadius = 3.8;
 
 function ReadRole(Name) {
   return getComputedStyle(document.documentElement).getPropertyValue(`--${Name}`).trim();
@@ -206,7 +209,8 @@ export default function GraphPane({
       }
       Node.Colour = ColourByDepth ? DepthColours[Depth % DepthColours.length] : Colours.Directory;
       if (ShrinkByDepth) {
-        Node.Radius = Math.max(SmallestDirectory, Node.Radius * Math.pow(ShrinkPerDepth, Depth));
+        const Step = Math.min(Depth, ShrinkDepth) / ShrinkDepth;
+        Node.Radius += (FileDotRadius - Node.Radius) * Step;
       }
     }
     // Anything but "Left" (including an old "Middle") pans with Right.