feat: allow dragging feature dialog

app.js

@@ -7,6 +7,7 @@ const FEATURE_INFO_LAYER_NAMES = new Set(["parcelas", "predios"]);
 const DEVICE_ORIENTATION_EVENTS = ["deviceorientationabsolute", "deviceorientation"];
 const COMPASS_HEADING_DEADBAND = 2;
 const SMALL_SCREEN_MEDIA_QUERY = "(max-width: 920px)";
+const MODAL_VIEWPORT_PADDING = 24;
 
 const els = {
   appShell: document.querySelector(".app-shell"),
@@ -21,6 +22,7 @@ const els = {
   parcelSearchStatus: document.getElementById("parcel-search-status"),
   backgroundSelect: document.getElementById("background-select"),
   featureModal: document.getElementById("feature-modal"),
+  featureModalDialog: document.querySelector(".feature-modal-dialog"),
   featureModalClose: document.getElementById("feature-modal-close"),
   featureModalKind: document.getElementById("feature-modal-kind"),
   featureArea: document.getElementById("feature-area"),
@@ -108,6 +110,7 @@ let lastCompassHeading;
 let pendingCompassHeading;
 let compassAnimationFrame;
 let deviceCompassFallbackTimer;
+let modalDrag;
 
 const map = new ol.Map({
   target: "map",
@@ -148,6 +151,10 @@ els.backgroundSelect.addEventListener("change", syncBackground);
 els.sidebarOpen.addEventListener("click", () => setSidebarCollapsed(false));
 els.sidebarClose.addEventListener("click", () => setSidebarCollapsed(true));
 els.featureModalClose.addEventListener("click", closeFeatureModal);
+els.featureModalDialog.addEventListener("pointerdown", startFeatureModalDrag);
+els.featureModalDialog.addEventListener("pointermove", dragFeatureModal);
+els.featureModalDialog.addEventListener("pointerup", stopFeatureModalDrag);
+els.featureModalDialog.addEventListener("pointercancel", stopFeatureModalDrag);
 els.featureModal.addEventListener("click", (event) => {
   if (event.target.matches("[data-feature-modal-close]")) {
     closeFeatureModal();
@@ -164,6 +171,7 @@ document.addEventListener("keydown", (event) => {
     }
   }
 });
+window.addEventListener("resize", keepFeatureModalInViewport);
 map.on("singleclick", showFeatureInformation);
 areaZoomInteraction.on("boxend", zoomToSelectedArea);
 areaZoomInteraction.on("boxcancel", () => {
@@ -745,9 +753,75 @@ function unqualifiedLayerName(name) {
 }
 
 function closeFeatureModal() {
+  resetFeatureModalPosition();
   els.featureModal.hidden = true;
 }
 
+function startFeatureModalDrag(event) {
+  if (event.button !== 0 || event.target.closest("button, a, input, select, textarea, label")) {
+    return;
+  }
+
+  const dialogRect = els.featureModalDialog.getBoundingClientRect();
+  els.featureModalDialog.style.position = "fixed";
+  els.featureModalDialog.style.left = `${dialogRect.left}px`;
+  els.featureModalDialog.style.top = `${dialogRect.top}px`;
+  els.featureModalDialog.style.margin = "0";
+  els.featureModalDialog.classList.add("is-dragging");
+  modalDrag = {
+    pointerId: event.pointerId,
+    offsetX: event.clientX - dialogRect.left,
+    offsetY: event.clientY - dialogRect.top,
+  };
+  els.featureModalDialog.setPointerCapture(event.pointerId);
+}
+
+function dragFeatureModal(event) {
+  if (!modalDrag || event.pointerId !== modalDrag.pointerId) {
+    return;
+  }
+
+  const dialogRect = els.featureModalDialog.getBoundingClientRect();
+  const maxLeft = Math.max(MODAL_VIEWPORT_PADDING, window.innerWidth - dialogRect.width - MODAL_VIEWPORT_PADDING);
+  const maxTop = Math.max(MODAL_VIEWPORT_PADDING, window.innerHeight - dialogRect.height - MODAL_VIEWPORT_PADDING);
+  const left = Math.min(maxLeft, Math.max(MODAL_VIEWPORT_PADDING, event.clientX - modalDrag.offsetX));
+  const top = Math.min(maxTop, Math.max(MODAL_VIEWPORT_PADDING, event.clientY - modalDrag.offsetY));
+
+  els.featureModalDialog.style.left = `${left}px`;
+  els.featureModalDialog.style.top = `${top}px`;
+}
+
+function stopFeatureModalDrag(event) {
+  if (!modalDrag || event.pointerId !== modalDrag.pointerId) {
+    return;
+  }
+
+  els.featureModalDialog.releasePointerCapture(event.pointerId);
+  els.featureModalDialog.classList.remove("is-dragging");
+  modalDrag = undefined;
+}
+
+function keepFeatureModalInViewport() {
+  if (els.featureModal.hidden || !els.featureModalDialog.style.left) {
+    return;
+  }
+
+  const dialogRect = els.featureModalDialog.getBoundingClientRect();
+  const maxLeft = Math.max(MODAL_VIEWPORT_PADDING, window.innerWidth - dialogRect.width - MODAL_VIEWPORT_PADDING);
+  const maxTop = Math.max(MODAL_VIEWPORT_PADDING, window.innerHeight - dialogRect.height - MODAL_VIEWPORT_PADDING);
+  els.featureModalDialog.style.left = `${Math.min(maxLeft, Math.max(MODAL_VIEWPORT_PADDING, dialogRect.left))}px`;
+  els.featureModalDialog.style.top = `${Math.min(maxTop, Math.max(MODAL_VIEWPORT_PADDING, dialogRect.top))}px`;
+}
+
+function resetFeatureModalPosition() {
+  modalDrag = undefined;
+  els.featureModalDialog.classList.remove("is-dragging");
+  els.featureModalDialog.style.removeProperty("position");
+  els.featureModalDialog.style.removeProperty("left");
+  els.featureModalDialog.style.removeProperty("top");
+  els.featureModalDialog.style.removeProperty("margin");
+}
+
 function formatFeatureArea(feature) {
   const properties = feature.properties || {};
   const areaEntry = Object.entries(properties).find(([name, value]) =>