Property panel: token[] view/edit, uniform row heights

- Add token[] attribute display: inline InputText (or Combo when
  allowedTokens metadata is present), collapsible [N tokens] tree
  for arrays with up to 32 editable entries
- Force all property table rows to GetFrameHeight() minimum via
  TableNextRow min_row_height so text-only and widget rows match
- Add AlignTextToFramePadding() before every TextUnformatted /
  TextDisabled / TextColored in cols 0-2 so short text sits centred
  in the uniform-height row rather than pinned to the top
- Wrap matrix attributes in TreeNodeEx [NxN] so they collapse to a
  single-height row; relationship targets use inline text / collapsible
  tree instead of a variable-height ListBox

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/ui/PropertyPanel.cpp

@@ -550,6 +550,7 @@ static void DrawPropertyMiniButton(const char* label, bool authored,
 
     ImGui::PushStyleColor(ImGuiCol_Text,   btnColor);
     ImGui::PushStyleColor(ImGuiCol_Button, ImVec4(0.f, 0.f, 0.f, 0.f));
+    ImGui::AlignTextToFramePadding();
     ImGui::SmallButton(label);
     ImGui::PopStyleColor(2);
 
@@ -841,19 +842,28 @@ static pxr::VtValue DrawVtValueWidget(pxr::UsdAttribute& attr,
         return VtValue();
     }
 
-    // ---- Matrices (multi-row, read-write) ----
+    // ---- Matrices: collapsed single row, expand to edit ----
-    auto drawMatrix = [](const char* id, ImGuiDataType dt, void* data, int rows, int cols) -> bool {
+    // Render rows inside a TreeNode so the table row stays one line tall
+    // when collapsed.  Expanded rows are user-initiated so taller is fine.
+    auto drawMatrix = [](const char* id, ImGuiDataType dt, void* data,
+                         int rows, int cols) -> bool {
         bool changed = false;
-        ImGui::PushID(id);
+        char hdr[24]; snprintf(hdr, sizeof(hdr), "[%dx%d]##%s", rows, cols, id);
-        for (int r = 0; r < rows; ++r) {
+        bool open = ImGui::TreeNodeEx(hdr,
-            char rowId[8]; snprintf(rowId, sizeof(rowId), "##r%d", r);
+            ImGuiTreeNodeFlags_AllowOverlap | ImGuiTreeNodeFlags_SpanAvailWidth);
-            ImGui::InputScalarN(rowId, dt,
+        if (open) {
-                static_cast<char*>(data) + r * cols * (dt == ImGuiDataType_Double ? 8 : 4),
+            ImGui::PushID(id);
-                cols, nullptr, nullptr,
+            for (int r = 0; r < rows; ++r) {
-                dt == ImGuiDataType_Double ? "%.4f" : "%.4f");
+                char rowId[8]; snprintf(rowId, sizeof(rowId), "##r%d", r);
-            changed |= ImGui::IsItemDeactivatedAfterEdit();
+                ImGui::SetNextItemWidth(-FLT_MIN);
+                ImGui::InputScalarN(rowId, dt,
+                    static_cast<char*>(data) + r * cols * (dt == ImGuiDataType_Double ? 8 : 4),
+                    cols, nullptr, nullptr, "%.4f");
+                changed |= ImGui::IsItemDeactivatedAfterEdit();
+            }
+            ImGui::PopID();
+            ImGui::TreePop();
         }
-        ImGui::PopID();
         return changed;
     };
 
@@ -890,29 +900,92 @@ static pxr::VtValue DrawVtValueWidget(pxr::UsdAttribute& attr,
 
     // ---- Token ----
     if (val.IsHolding<TfToken>()) {
+        ImGui::AlignTextToFramePadding();
         ImGui::TextUnformatted(val.UncheckedGet<TfToken>().GetText());
         return VtValue();
     }
 
     // ---- String / AssetPath ----
     if (val.IsHolding<std::string>()) {
+        ImGui::AlignTextToFramePadding();
         ImGui::TextUnformatted(val.UncheckedGet<std::string>().c_str());
         return VtValue();
     }
     if (val.IsHolding<SdfAssetPath>()) {
+        ImGui::AlignTextToFramePadding();
         ImGui::TextUnformatted(val.UncheckedGet<SdfAssetPath>().GetAssetPath().c_str());
         return VtValue();
     }
 
-    // ---- Token array (editable inline) ----
+    // ---- Token array: view + edit ----
     if (val.IsHolding<VtArray<TfToken>>()) {
-        const auto& arr = val.UncheckedGet<VtArray<TfToken>>();
+        VtArray<TfToken> arr = val.UncheckedGet<VtArray<TfToken>>();
-        ImGui::TextDisabled("[%zu tokens]", arr.size());
+        bool changed = false;
+
+        // Optional allowedTokens → show Combo per element instead of InputText.
+        VtValue allowedMeta;
+        attr.GetMetadata(TfToken("allowedTokens"), &allowedMeta);
+        const VtArray<TfToken>* allowed =
+            (!allowedMeta.IsEmpty() && allowedMeta.IsHolding<VtArray<TfToken>>())
+            ? &allowedMeta.UncheckedGet<VtArray<TfToken>>()
+            : nullptr;
+
+        // Widget for one element (combo or free-text).
+        auto drawOne = [&](int idx) {
+            ImGui::PushID(idx);
+            if (allowed) {
+                std::string cur = arr[idx].GetString();
+                ImGui::SetNextItemWidth(-FLT_MIN);
+                if (ImGui::BeginCombo("##tc", cur.c_str())) {
+                    for (const auto& tok : *allowed) {
+                        bool sel = (tok == arr[idx]);
+                        if (ImGui::Selectable(tok.GetText(), sel))
+                            { arr[idx] = tok; changed = true; }
+                        if (sel) ImGui::SetItemDefaultFocus();
+                    }
+                    ImGui::EndCombo();
+                }
+            } else {
+                char buf[256];
+                snprintf(buf, sizeof(buf), "%s", arr[idx].GetText());
+                ImGui::SetNextItemWidth(-FLT_MIN);
+                ImGui::InputText("##te", buf, sizeof(buf));
+                if (ImGui::IsItemDeactivatedAfterEdit())
+                    { arr[idx] = TfToken(buf); changed = true; }
+            }
+            ImGui::PopID();
+        };
+
+        if (arr.empty()) {
+            ImGui::AlignTextToFramePadding();
+            ImGui::TextDisabled("[empty]");
+        } else if (arr.size() == 1) {
+            drawOne(0);
+        } else {
+            bool open = ImGui::TreeNodeEx("##tarr",
+                ImGuiTreeNodeFlags_AllowOverlap | ImGuiTreeNodeFlags_SpanAvailWidth);
+            ImGui::SameLine(0, 6);
+            ImGui::TextDisabled("[%zu tokens]", arr.size());
+            if (open) {
+                static constexpr size_t kLimit = 32;
+                size_t lim = std::min(arr.size(), kLimit);
+                for (size_t i = 0; i < lim; ++i) {
+                    ImGui::Text("[%d]", (int)i);
+                    ImGui::SameLine();
+                    drawOne((int)i);
+                }
+                if (arr.size() > kLimit)
+                    ImGui::TextDisabled("  ... %zu more", arr.size() - kLimit);
+                ImGui::TreePop();
+            }
+        }
+        if (changed) return VtValue(arr);
         return VtValue();
     }
 
     // ---- Large arrays: just show size ----
     if (val.IsArrayValued() && val.GetArraySize() > 5) {
+        ImGui::AlignTextToFramePadding();
         ImGui::TextDisabled("[array  %zu]", val.GetArraySize());
         return VtValue();
     }
@@ -923,6 +996,7 @@ static pxr::VtValue DrawVtValueWidget(pxr::UsdAttribute& attr,
         oss << val;
         std::string s = oss.str();
         if (s.size() > 120) { s.resize(120); s += " ..."; }
+        ImGui::AlignTextToFramePadding();
         ImGui::TextUnformatted(s.c_str());
     }
     return VtValue();
@@ -1056,11 +1130,12 @@ void PropertyPanel::RenderPropertiesTable(const pxr::UsdPrim& prim) {
     // No TableHeadersRow – matches usdtweak "no header" intent
 
     const pxr::UsdEditTarget& editTarget = prim.GetStage()->GetEditTarget();
+    const float rowH = ImGui::GetFrameHeight();
     int uid = 0;
 
     // ---- Attributes (mirrors usdtweak attribute loop) ----
     for (auto& attr : prim.GetAttributes()) {
-        ImGui::TableNextRow();
+        ImGui::TableNextRow(ImGuiTableRowFlags_None, rowH);
 
         // Col 0 – mini button "(a)"
         ImGui::TableSetColumnIndex(0);
@@ -1073,6 +1148,7 @@ void PropertyPanel::RenderPropertiesTable(const pxr::UsdPrim& prim) {
 
         // Col 1 – display name  (namespace:basename)
         ImGui::TableSetColumnIndex(1);
+        ImGui::AlignTextToFramePadding();
         ImGui::TextUnformatted(GetPropDisplayName(attr).c_str());
 
         // Col 2 – value widget with PushItemWidth(-FLT_MIN)  (label hidden)
@@ -1109,9 +1185,12 @@ void PropertyPanel::RenderPropertiesTable(const pxr::UsdPrim& prim) {
         } else if (attr.HasAuthoredConnections()) {
             SdfPathVector conns;
             attr.GetConnections(&conns);
-            if (!conns.empty())
+            if (!conns.empty()) {
+                ImGui::AlignTextToFramePadding();
                 ImGui::TextDisabled("-> %s", conns[0].GetString().c_str());
+            }
         } else {
+            ImGui::AlignTextToFramePadding();
             ImGui::TextDisabled("no value");
         }
 
@@ -1121,7 +1200,7 @@ void PropertyPanel::RenderPropertiesTable(const pxr::UsdPrim& prim) {
 
     // ---- Relationships (mirrors usdtweak relationship loop) ----
     for (const auto& rel : prim.GetRelationships()) {
-        ImGui::TableNextRow();
+        ImGui::TableNextRow(ImGuiTableRowFlags_None, rowH);
 
         // Col 0 – mini button "(r)"
         ImGui::TableSetColumnIndex(0);
@@ -1136,24 +1215,36 @@ void PropertyPanel::RenderPropertiesTable(const pxr::UsdPrim& prim) {
         ImVec4 relColor = rel.IsAuthored()
             ? ImVec4(0.6f, 0.9f, 1.f, 1.f)
             : ImVec4(0.5f, 0.5f, 0.5f, 1.f);
+        ImGui::AlignTextToFramePadding();
         ImGui::TextColored(relColor, "%s", GetPropDisplayName(rel).c_str());
 
-        // Col 2 – target list  (mirrors DrawUsdRelationshipList in usdtweak)
+        // Col 2 – target list: single row when collapsed, expand for multiple
         ImGui::TableSetColumnIndex(2);
         SdfPathVector targets;
         rel.GetTargets(&targets);
         if (targets.empty()) {
+            ImGui::AlignTextToFramePadding();
             ImGui::TextDisabled("no targets");
+        } else if (targets.size() == 1) {
+            ImGui::AlignTextToFramePadding();
+            ImGui::TextDisabled("%s", targets[0].GetString().c_str());
+            if (ImGui::IsItemHovered())
+                ImGui::SetTooltip("%s", targets[0].GetString().c_str());
         } else {
             ImGui::PushID(rel.GetPath().GetString().c_str());
-            float listH = static_cast<float>(targets.size()) * 25.f;
+            bool open = ImGui::TreeNodeEx("##rtarr",
-            if (ImGui::BeginListBox("##rl", ImVec2(-FLT_MIN, listH))) {
+                ImGuiTreeNodeFlags_AllowOverlap | ImGuiTreeNodeFlags_SpanAvailWidth);
+            ImGui::SameLine(0, 6);
+            ImGui::TextDisabled("[%zu targets]", targets.size());
+            if (open) {
                 for (const auto& path : targets) {
                     ImGui::PushID(path.GetString().c_str());
-                    ImGui::TextUnformatted(path.GetString().c_str());
+                    ImGui::TextDisabled("%s", path.GetString().c_str());
+                    if (ImGui::IsItemHovered())
+                        ImGui::SetTooltip("%s", path.GetString().c_str());
                     ImGui::PopID();
                 }
-                ImGui::EndListBox();
+                ImGui::TreePop();
             }
             ImGui::PopID();
         }