+ /* We've measured everything so far in "client rect"
+ * coordinates, because that's the only available measurement
+ * we have for the width of the <text> element after futzing
+ * with its contents. But when we reposition that <text>
+ * element, it will be by adjusting its "x" attribute, and
+ * that attribute uses a different coordinate system than the
+ * client rect does. Specifically, "x" refers to an offset
+ * within the SVG's coordinate system, and the client rect
+ * coordinates are pixels on-screen. To convert between the
+ * two, we can take the "width" attribute of the background
+ * element and compare it to the width of the background
+ * element's client rect. Since the size of the background is
+ * fixed, this should give us a multiplier that turns client recr
+ * distances (what we have) into SVG distances (what we want) */
+ const client_to_svg = parseFloat(bg.getAttribute("width"))/r1.width;
+
+ /* Convert hdelta from client rect to SVG coordinates */
+ const svg_hdelta = hdelta * client_to_svg;
+