web: expand tile bounds to include outward pin labels

The tile grid was sized to cover the die plus pin marker size, but
not the label text that extends outward from each die edge (matching
the Qt GUI placement).  Pin labels at the die boundary were clipped
because no tiles existed beyond the marker margin.

Expand getBounds() to account for the full label extent — marker
size + text margin + longest BTerm name width — converted to DBU at
the critical zoom where labels first appear.  The same bounds feed
both server tile mapping and the client bounds response, so the
client automatically requests tiles for the expanded area.

Signed-off-by: Matt Liberty <mliberty@precisioninno.com>

Author: maliberty

src/web/src/tile_generator.cpp

@@ -395,9 +395,22 @@ odb::Rect TileGenerator::getBounds() const
   odb::Rect bounds;
   if (odb::dbBlock* block = getBlock()) {
     bounds = block->getBBox()->getBox();
-    // Expand for pin markers that extend outside the die edge.
-    const int margin = getPinMaxSize();
-    if (margin > 0) {
+    // Expand for pin markers AND labels that extend outside the die edge.
+    // At the zoom where labels first appear, the label extends
+    //   marker_px + text_margin + text_width  pixels
+    // past the pin anchor.  Convert to DBU by dividing by the critical
+    // scale (= kMinPinNameSizePixels / pin_size).
+    const int pin_size = getPinMaxSize();
+    if (pin_size > 0) {
+      int max_text_px = 0;
+      for (odb::dbBTerm* term : block->getBTerms()) {
+        const int w = fontAtlasTextWidth(term->getName(), kPinLabelFontHeight);
+        if (w > max_text_px) {
+          max_text_px = w;
+        }
+      }
+      const int label_px = kMinPinNameSizePixels + 3 + max_text_px;
+      const int margin = label_px * pin_size / kMinPinNameSizePixels;
       bounds.set_xlo(bounds.xMin() - margin);
       bounds.set_ylo(bounds.yMin() - margin);
       bounds.set_xhi(bounds.xMax() + margin);