web: cache pin label margin to avoid per-tile BTerms iteration

Move the max-text-width-across-all-BTerms computation out of getBounds()
into computePinLabelMargin(), called from the constructor and eagerInit().
The cached margin (in DBU) is reused on every getBounds() call, avoiding
an O(N) iteration over all pins on every tile request.

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

Author: maliberty

src/web/src/tile_generator.cpp

@@ -21,6 +21,7 @@
 #include "color.h"
 #include "db_sta/dbSta.hh"
 #include "font_atlas.h"
+#include "glyph_cache.h"
 #include "gui/gui.h"
 #include "gui/heatMap.h"
 #include "json_builder.h"
@@ -280,6 +281,7 @@ TileGenerator::TileGenerator(odb::dbDatabase* db,
   if (chip) {
     search_->setTopChip(chip);
   }
+  computePinLabelMargin();
 }
 
 TileGenerator::~TileGenerator() = default;
@@ -294,6 +296,29 @@ void TileGenerator::eagerInit()
   if (block) {
     search_->eagerInit(block);
   }
+  computePinLabelMargin();
+}
+
+void TileGenerator::computePinLabelMargin()
+{
+  odb::dbBlock* block = getBlock();
+  if (!block) {
+    pin_label_margin_dbu_ = 0;
+    return;
+  }
+  const int pin_size = getPinMaxSize();
+  if (pin_size <= 0) {
+    pin_label_margin_dbu_ = 0;
+    return;
+  }
+  int max_text_px = 0;
+  const auto pin_font = fontAtlasGetFont(kPinLabelFontHeight);
+  for (odb::dbBTerm* term : block->getBTerms()) {
+    const int w = pin_font.textWidth(term->getName());
+    max_text_px = std::max(w, max_text_px);
+  }
+  const int label_px = kMinPinNameSizePixels + 3 + max_text_px;
+  pin_label_margin_dbu_ = label_px * pin_size / kMinPinNameSizePixels;
 }
 
 bool TileGenerator::shapesReady() const
@@ -395,25 +420,11 @@ odb::Rect TileGenerator::getBounds() const
   odb::Rect bounds;
   if (odb::dbBlock* block = getBlock()) {
     bounds = block->getBBox()->getBox();
-    // 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;
-      const auto pin_font = fontAtlasGetFont(kPinLabelFontHeight);
-      for (odb::dbBTerm* term : block->getBTerms()) {
-        const int w = pin_font.textWidth(term->getName());
-        max_text_px = std::max(w, max_text_px);
-      }
-      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);
-      bounds.set_yhi(bounds.yMax() + margin);
+    if (pin_label_margin_dbu_ > 0) {
+      bounds.set_xlo(bounds.xMin() - pin_label_margin_dbu_);
+      bounds.set_ylo(bounds.yMin() - pin_label_margin_dbu_);
+      bounds.set_xhi(bounds.xMax() + pin_label_margin_dbu_);
+      bounds.set_yhi(bounds.yMax() + pin_label_margin_dbu_);
     }
   }
   return bounds;

src/web/src/tile_generator.h

@@ -355,10 +355,13 @@ class TileGenerator
                        const Color& c,
                        int width = 3);
 
+  void computePinLabelMargin();
+
   odb::dbDatabase* db_;
   sta::dbSta* sta_;
   utl::Logger* logger_;
   std::unique_ptr<Search> search_;
+  int pin_label_margin_dbu_ = 0;  // cached by computePinLabelMargin()
   static constexpr int kTileSizeInPixel = 256;
 };
 

src/web/test/cpp/CMakeLists.txt

@@ -62,9 +62,23 @@ gtest_discover_tests(TestDebugGraphics
   WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/..
 )
 
+add_executable(TestGlyphCache TestGlyphCache.cpp)
+
+target_link_libraries(TestGlyphCache ${TEST_LIBS})
+
+target_include_directories(TestGlyphCache
+  PRIVATE
+    ${CMAKE_CURRENT_SOURCE_DIR}/../../src
+)
+
+gtest_discover_tests(TestGlyphCache
+  WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/..
+)
+
 add_dependencies(build_and_test
   TestTileGenerator
   TestRequestHandler
   TestSaveReport
   TestDebugGraphics
+  TestGlyphCache
 )