web: add DRC viewer widget

[openroad-ci]

Summary

Add a DRC (Design Rule Check) viewer to the web UI with:

• Server-side handlers for categories, markers, report loading, marker updates, and violation highlighting
• Client-side DRC widget with category selector, violation tree, load/highlight, and file upload dialog
• DRC overlay rendering in the tile generator
• C++ and JS tests for the new functionality

Type of Change

• New feature

Impact

DRC viewer works

Verification

• I have verified that the local build succeeds (./etc/Build.sh).
• I have run the relevant tests and they pass.
• My code follows the repository's formatting guidelines.
• I have signed my commits (DCO).

[gemini-code-assist]

Code Review

This pull request introduces a comprehensive DRC (Design Rule Check) viewer widget for the web-based GUI, mirroring the functionality of the Qt-based DRCWidget. It includes a new frontend DrcWidget for category selection and violation tree navigation, alongside a backend DRCHandler to manage marker data, report loading, and overlay rendering. While the implementation successfully integrates DRC visualization into the tile-based rendering system, several performance and robustness issues were identified. Specifically, toggling category visibility triggers a flood of individual WebSocket requests, and the backend relies on inefficient ODB marker iterations (getAllMarkers) which can cause significant lag in designs with many violations. Additionally, the report loading logic uses a hardcoded category name, which will cause conflicts when attempting to load multiple reports.

[gemini-code-assist]

This function is inefficient for two reasons:

1. It calls category->getAllMarkers(), which in ODB allocates and populates a new std::vector containing all markers in the hierarchy every time it is called. For large reports, this is expensive.
2. It does not check if marker_id is valid (e.g., -1 for deselect) before performing the linear scan.

Adding an early exit for invalid IDs and considering a more efficient lookup (like a map in SessionState) would improve responsiveness.

odb::dbMarker* DRCHandler::findMarkerById(SessionState& state,
                                          odb::dbChip* chip,
                                          int marker_id)
{
  if (marker_id < 0) {
    return nullptr;
  }
  std::lock_guard<std::mutex> lock(state.drc_mutex);
  if (state.active_drc_category.empty()) {
    return nullptr;
  }
  odb::dbMarkerCategory* category
      = chip->findMarkerCategory(state.active_drc_category.c_str());
  if (!category) {
    return nullptr;
  }
  for (odb::dbMarker* marker : category->getAllMarkers()) {
    if (static_cast<int>(marker->getId()) == marker_id) {
      return marker;
    }
  }
  return nullptr;
}

[gemini-code-assist]

Calling getAllMarkers() inside refreshDRCOverlay causes a full iteration and vector allocation every time a single marker's visibility is toggled. For reports with a high volume of violations, this will lead to noticeable lag in the UI. Consider caching the marker list in SessionState when a category is first selected.

[gemini-code-assist]

The category name "DRC" is hardcoded. If a user attempts to load a second DRC report, odb::dbMarkerCategory::fromTR will attempt to create another category with the same name, which will likely fail or throw an exception because ODB requires unique category names at the same level.

Consider using the filename (stem) to generate a unique category name or checking if the category already exists and prompting the user/overwriting it.

[github-actions]

clang-tidy review says "All clean, LGTM! 👍"

[github-actions]

clang-tidy review says "All clean, LGTM! 👍"