Improve label readability with collision suppression and zoom density

frontend/app.js

@@ -381,6 +381,11 @@ function saveSnapshot() {
 function updateTransform() {
   el.canvasInner.style.transform = `translate(${state.panX}px, ${state.panY}px) scale(${state.scale})`;
   el.zoomResetBtn.textContent = `${Math.round(state.scale * 100)}%`;
+  const svg = el.canvasInner.querySelector("svg");
+  if (svg) {
+    applyLabelDensityByZoom(svg);
+    resolveLabelCollisions(svg);
+  }
 }
 
 function fitView(layout) {
@@ -589,6 +594,114 @@ function setLabelLayerVisibility() {
   if (layer) {
     layer.style.display = state.showLabels ? "" : "none";
   }
+  applyLabelDensityByZoom(svg);
+  resolveLabelCollisions(svg);
+}
+
+function boxesOverlap(a, b, pad = 2) {
+  return !(a.right + pad < b.left || a.left - pad > b.right || a.bottom + pad < b.top || a.top - pad > b.bottom);
+}
+
+function labelPriority(node) {
+  if (node.hasAttribute("data-net-label")) return 4;
+  if (node.hasAttribute("data-ref-label")) return 3;
+  if (node.hasAttribute("data-pin-label")) return 2;
+  if (node.hasAttribute("data-value-label")) return 1;
+  return 0;
+}
+
+function applyLabelDensityByZoom(svg) {
+  const pinLabels = svg.querySelectorAll("[data-pin-label]");
+  const valueLabels = svg.querySelectorAll("[data-value-label]");
+  const refLabels = svg.querySelectorAll("[data-ref-label]");
+  const dense = state.scale < 0.85;
+  const veryDense = state.scale < 0.65;
+
+  pinLabels.forEach((n) => {
+    n.style.display = dense ? "none" : "";
+  });
+  valueLabels.forEach((n) => {
+    n.style.display = veryDense ? "none" : "";
+  });
+  refLabels.forEach((n) => {
+    n.style.display = veryDense ? "none" : "";
+  });
+}
+
+function resolveLabelCollisions(svg) {
+  if (!state.showLabels) {
+    return;
+  }
+
+  const labels = [
+    ...svg.querySelectorAll("[data-net-label], [data-pin-label], [data-ref-label], [data-value-label]")
+  ].filter((n) => n.style.display !== "none");
+
+  for (const n of labels) {
+    n.style.visibility = "";
+  }
+
+  const netSeen = [];
+  for (const node of labels) {
+    const net = node.getAttribute("data-net-label");
+    if (!net) {
+      continue;
+    }
+    const box = node.getBoundingClientRect();
+    let dup = false;
+    for (const prev of netSeen) {
+      if (prev.net !== net) {
+        continue;
+      }
+      const dx = Math.abs((box.left + box.right) / 2 - prev.cx);
+      const dy = Math.abs((box.top + box.bottom) / 2 - prev.cy);
+      if (dx < 30 && dy < 18) {
+        dup = true;
+        break;
+      }
+    }
+    if (dup) {
+      node.style.visibility = "hidden";
+      continue;
+    }
+    netSeen.push({
+      net,
+      cx: (box.left + box.right) / 2,
+      cy: (box.top + box.bottom) / 2
+    });
+  }
+
+  const active = labels.filter((n) => n.style.display !== "none" && n.style.visibility !== "hidden");
+  const entries = active.map((node) => ({
+    node,
+    priority: labelPriority(node),
+    box: node.getBoundingClientRect()
+  }));
+
+  for (let i = 0; i < entries.length; i += 1) {
+    const a = entries[i];
+    if (a.node.style.visibility === "hidden") {
+      continue;
+    }
+    for (let j = i + 1; j < entries.length; j += 1) {
+      const b = entries[j];
+      if (b.node.style.visibility === "hidden") {
+        continue;
+      }
+      if (!boxesOverlap(a.box, b.box, 1)) {
+        continue;
+      }
+
+      if (a.priority === b.priority) {
+        b.node.style.visibility = "hidden";
+      } else if (a.priority > b.priority) {
+        b.node.style.visibility = "hidden";
+      } else {
+        a.node.style.visibility = "hidden";
+        break;
+      }
+    }
+  }
 }
 
 function renderInstances() {
@@ -1197,6 +1310,11 @@ function renderCanvas() {
   bindSvgInteractions();
   applyVisualHighlight();
   updateTransform();
+  const svg = el.canvasInner.querySelector("svg");
+  if (svg) {
+    applyLabelDensityByZoom(svg);
+    resolveLabelCollisions(svg);
+  }
 }
 
 function renderAll() {

src/render.js

@@ -437,8 +437,8 @@ export function renderSvgFromLayout(model, layout, options = {}) {
     ${pinCoreSvg}
   </g>
   ${pinLabelsSvg}
-  <text x="${x + 8}" y="${refY}" font-size="${compactLabel ? 11 : 12}" font-weight="700" fill="#111827" stroke="#f8fafc" stroke-width="2.2" paint-order="stroke fill">${esc(refLabel)}</text>
+  <text x="${x + 8}" y="${refY}" font-size="${compactLabel ? 11 : 12}" font-weight="700" fill="#111827" stroke="#f8fafc" stroke-width="2.2" paint-order="stroke fill" data-ref-label="${esc(inst.ref)}">${esc(refLabel)}</text>
-  <text x="${x + 8}" y="${valueY}" font-size="${compactLabel ? 9 : 10}" fill="#667085" stroke="#f8fafc" stroke-width="2" paint-order="stroke fill">${esc(valueLabel)}</text>
+  <text x="${x + 8}" y="${valueY}" font-size="${compactLabel ? 9 : 10}" fill="#667085" stroke="#f8fafc" stroke-width="2" paint-order="stroke fill" data-value-label="${esc(inst.ref)}">${esc(valueLabel)}</text>
 </g>`;
     })
     .join("\n");