+
+ /************************/
+ /* Set the service zone */
+ /************************/
+ function set_service_zone(event, zone) {
+ /* We can take the zone as a parameter too; this allows us to
+ * use this function for the (computed) MARC Train zone and
+ * not just the querystring Commuter Bus zone. The extra
+ * "event" parameter is there for the event listener, which
+ * would otherwise stuff an onload event into the zone
+ * parameter. "Thankfully" javascript lets us call a
+ * two-argument function with one argument and thereby abuse
+ * the event handler for this. */
+ const z = document.getElementById("zone");
+ const params = new URLSearchParams(document.location.search);
+
+ if (zone) {
+ z.textContent = zone;
+ z.style.display = "block"; /* It's hidden by default */
+ }
+ else if (params.get("zone")) {
+ /* Get the "zone" from the querystring if it's there */
+ z.textContent = params.get("zone");
+ z.style.display = "block"; /* It's hidden by default */
+ }
+
+ /* Otherwise, leave it blank (and hidden) */
+ }
+
+ /***********************************************************/
+ /* Resize the ticket background based on the service name */
+ /***********************************************************/
+
+ function resize_ticket() {
+ /* Get the "servicename" from the querystring if it's there */
+ const params = new URLSearchParams(document.location.search);
+ const tbg = document.getElementById("ticketbg");
+ const t = document.getElementById("ticket");
+ const sn = document.getElementById("servicename");
+
+ if (params.get("servicename") == "Commuter Bus") {
+ /* The top of the background is initially at y=246.859, and
+ * we scale it by a factor of 1.12 to y=276.482 for a change
+ * of 29.623. So after we scale it, we translate it upwards
+ * by that amount to put it back where it started. */
+ tbg.setAttribute("transform", "translate(0 -29.623) scale(1 1.12)");
+
+ /* Now translate the entire ticket up by the magic amount, 1/5
+ * of the size change we made to the background. This ratio
+ * was found by measuring pixels in side-by-side screenshots
+ * of BaltimoreLink and Commuter Bus tickets. */
+ t.setAttribute("transform", "translate(0 -9.33)");
+
+ /* More magic numbers discovered by comparing the two
+ * tickets overlayed in inkscape */
+ sn.setAttribute("transform", "translate(0 64.28)");
+ }
+ else if (params.get("servicename") == "MARC Train") {
+ /* insane tricks are explained above */
+ tbg.setAttribute("transform",
+ "translate(0 -72.378) scale(1 1.2932)");
+ t.setAttribute("transform", "translate(0 -67.17)");
+ sn.setAttribute("transform", "translate(0 131.0)");
+ }
+
+ /* Otherwise, leave it alone. The SVG was designed with the
+ * BaltimoreLink ticket in mind */
+ }
+
+ /****************************************/
+ /* Set and reposition the security code */
+ /****************************************/
+
+ function set_code() {
+ const ct = document.getElementById("codetext");
+
+ /* Get the "code" from the querystring if it's there */
+ const params = new URLSearchParams(document.location.search);
+ if (params.get("code")) {
+ ct.textContent = params.get("code").toUpperCase();
+ }
+ else {
+ /* Otherwise, use a random code */
+ const bucket = ["0","1","2","3","4","5","6","7","8","9",
+ "A","B","C","D","E","F","G","H","I","J",
+ "K","L","M","N","O","P","Q","R","S","T",
+ "U","V","W","X","Y","Z"];
+
+ /* Two random ints between 0 and 35 */
+ const i1 = Math.floor(Math.random() * 36);
+ const i2 = Math.floor(Math.random() * 36);
+ const d1 = bucket[i1];
+ const d2 = bucket[i2];
+ ct.textContent = d1 + d2;
+ }
+ }
+
+
+ function center_code() {
+ /* Center the security code inside its red box */
+ const ct = document.getElementById("codetext");
+ const bg = document.getElementById("codebg");
+
+ /* First, find the center of the red box */
+ const r1 = bg.getBoundingClientRect();
+ const c1 = r1.left + (r1.width / 2);
+
+ /* Now the center of the code text */
+ const r2 = ct.getBoundingClientRect();
+ const c2 = r2.left + (r2.width / 2);
+
+ /* What do we add to c2 to make it equal to c1? */
+ const hdelta = c1 - c2;
+
+ /* 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;
+
+ /* Since this <text> element has an "x" attribute it's easier for
+ * us to shift that than it is to mess with the "left" style. */
+ ct.setAttribute("x", parseFloat(ct.getAttribute("x")) + svg_hdelta);