feat(ui): move editing context breadcrumb to viewport overlay (#232)

Convert BreadcrumbToolBar from a QToolBar in the MainWindow toolbar area
to a QFrame overlay at the top-left of each 3D viewport.

Changes:
- BreadcrumbToolBar: change base class from QToolBar to QFrame, use
  QHBoxLayout instead of toolbar actions, semi-transparent overlay
  background with rounded corners
- MainWindow: remove breadcrumb toolbar creation, toolbar break, and
  signal connection
- View3DInventor: create per-view BreadcrumbToolBar as a child of the
  GL viewer widget, positioned at (8,8) with event filter to keep it
  raised on viewport resize

Each 3D view now has its own breadcrumb instance connected to the
EditingContextResolver singleton. This reclaims the full-width toolbar
row and keeps the editing context visually tied to the viewport.

src/Gui/BreadcrumbToolBar.cpp

@@ -26,6 +26,7 @@
 #include "EditingContext.h"
 
 #include <QColor>
+#include <QHBoxLayout>
 #include <QLabel>
 #include <QToolButton>
 
@@ -40,7 +41,6 @@ using namespace Gui;
 
 static QString chipStyle(const QString& bgHex)
 {
-    // Darken background slightly for contrast, use white text
     QColor bg(bgHex);
     QColor textColor(QStringLiteral("#cdd6f4"));  // Catppuccin Text
 
@@ -81,24 +81,25 @@ static QString separatorStyle()
 // ---------------------------------------------------------------------------
 
 BreadcrumbToolBar::BreadcrumbToolBar(QWidget* parent)
-    : QToolBar(parent)
+    : QFrame(parent)
 {
     setObjectName(QStringLiteral("BreadcrumbToolBar"));
-    setWindowTitle(tr("Editing Context"));
-    setMovable(false);
-    setFloatable(false);
-    setIconSize(QSize(16, 16));
 
-    // Thin toolbar with minimal margins
+    _layout = new QHBoxLayout(this);
+    _layout->setContentsMargins(6, 4, 6, 4);
+    _layout->setSpacing(2);
+
+    // Semi-transparent overlay background
     setStyleSheet(QStringLiteral(
-        "QToolBar {"
-        "  background: #1e1e2e;"  // Catppuccin Base
-        "  border: none;"
-        "  spacing: 2px;"
-        "  padding: 2px 4px;"
-        "  max-height: 24px;"
+        "QFrame#BreadcrumbToolBar {"
+        "  background-color: rgba(30, 30, 46, 200);"  // Catppuccin Base, ~78% opacity
+        "  border: 1px solid rgba(69, 71, 90, 150);"  // Surface1
+        "  border-radius: 6px;"
         "}"
     ));
+
+    setSizePolicy(QSizePolicy::Minimum, QSizePolicy::Fixed);
+    setFixedHeight(28);
 }
 
 
@@ -110,6 +111,7 @@ void BreadcrumbToolBar::updateContext(const EditingContext& ctx)
 {
     clearSegments();
     buildSegments(ctx);
+    adjustSize();
 }
 
 
@@ -120,17 +122,16 @@ void BreadcrumbToolBar::updateContext(const EditingContext& ctx)
 void BreadcrumbToolBar::clearSegments()
 {
     for (auto* btn : _segments) {
-        removeAction(btn->defaultAction());
+        _layout->removeWidget(btn);
         delete btn;
     }
     _segments.clear();
 
     for (auto* sep : _separators) {
+        _layout->removeWidget(sep);
         delete sep;
     }
     _separators.clear();
-
-    clear();
 }
 
 void BreadcrumbToolBar::buildSegments(const EditingContext& ctx)
@@ -144,7 +145,7 @@ void BreadcrumbToolBar::buildSegments(const EditingContext& ctx)
         if (i > 0) {
             auto* sep = new QLabel(QStringLiteral("\u203A"));  // › character
             sep->setStyleSheet(separatorStyle());
-            addWidget(sep);
+            _layout->addWidget(sep);
             _separators.append(sep);
         }
 
@@ -168,7 +169,7 @@ void BreadcrumbToolBar::buildSegments(const EditingContext& ctx)
             segmentClicked(segmentIndex);
         });
 
-        addWidget(btn);
+        _layout->addWidget(btn);
         _segments.append(btn);
     }
 }

src/Gui/BreadcrumbToolBar.h

@@ -25,10 +25,11 @@
 #ifndef GUI_BREADCRUMBTOOLBAR_H
 #define GUI_BREADCRUMBTOOLBAR_H
 
-#include <QToolBar>
+#include <QFrame>
 #include <QList>
 #include <FCGlobal.h>
 
+class QHBoxLayout;
 class QToolButton;
 class QLabel;
 
@@ -38,11 +39,14 @@ namespace Gui
 struct EditingContext;
 
 /**
- * A thin toolbar that displays the current editing context as color-coded
- * breadcrumb segments.  Each segment is a clickable QToolButton; clicking
- * a parent segment navigates up (exits the current edit, etc.).
+ * A small overlay widget that displays the current editing context as
+ * color-coded breadcrumb segments.  Each segment is a clickable QToolButton;
+ * clicking a parent segment navigates up (exits the current edit, etc.).
+ *
+ * Intended to be parented to the 3D viewport widget so it floats at the
+ * top-left corner of the view.
  */
-class GuiExport BreadcrumbToolBar: public QToolBar
+class GuiExport BreadcrumbToolBar: public QFrame
 {
     Q_OBJECT
 
@@ -59,6 +63,7 @@ private:
     void clearSegments();
     void buildSegments(const EditingContext& ctx);
 
+    QHBoxLayout* _layout;
     QList<QToolButton*> _segments;
     QList<QLabel*> _separators;
 };

src/Gui/MainWindow.cpp

@@ -105,8 +105,7 @@
 #include "SelectionView.h"
 #include "SplashScreen.h"
 #include "StatusBarLabel.h"
-#include "BreadcrumbToolBar.h"
-#include "EditingContext.h"
+
 #include "ToolBarManager.h"
 #include "ToolBoxManager.h"
 #include "Tree.h"
@@ -307,7 +306,6 @@ struct MainWindowP
     QLabel* actionLabel;
     InputHintWidget* hintLabel;
     QLabel* rightSideLabel;
-    BreadcrumbToolBar* breadcrumbBar = nullptr;
     QTimer* actionTimer;
     QTimer* statusTimer;
     QTimer* activityTimer;
@@ -492,20 +490,6 @@ MainWindow::MainWindow(QWidget* parent, Qt::WindowFlags f)
 #endif
     connect(d->mdiArea, &QMdiArea::subWindowActivated, this, &MainWindow::onWindowActivated);
 
-    // Breadcrumb toolbar for editing context display
-    d->breadcrumbBar = new BreadcrumbToolBar(this);
-    addToolBar(Qt::TopToolBarArea, d->breadcrumbBar);
-    insertToolBarBreak(d->breadcrumbBar);
-
-    // Initialize the editing context resolver and connect to breadcrumb
-    auto* ctxResolver = EditingContextResolver::instance();
-    connect(
-        ctxResolver,
-        &EditingContextResolver::contextChanged,
-        d->breadcrumbBar,
-        &BreadcrumbToolBar::updateContext
-    );
-
     setupDockWindows();
 
     // accept drops on the window, get handled in dropEvent, dragEnterEvent

src/Gui/View3DInventor.cpp

@@ -60,7 +60,9 @@
 #include "View3DInventor.h"
 #include "View3DSettings.h"
 #include "Application.h"
+#include "BreadcrumbToolBar.h"
 #include "BitmapFactory.h"
+#include "EditingContext.h"
 #include "Camera.h"
 #include "Document.h"
 #include "FileDialog.h"
@@ -145,6 +147,19 @@ View3DInventor::View3DInventor(
     // apply the user settings
     applySettings();
 
+    // Breadcrumb overlay at top-left of viewport
+    _breadcrumb = new BreadcrumbToolBar(_viewer->getWidget());
+    _breadcrumb->move(8, 8);
+    _breadcrumb->raise();
+    _breadcrumb->show();
+    _viewer->getWidget()->installEventFilter(this);
+
+    auto* ctxResolver = EditingContextResolver::instance();
+    connect(ctxResolver, &EditingContextResolver::contextChanged,
+            _breadcrumb, &BreadcrumbToolBar::updateContext);
+    // Apply the current context immediately
+    _breadcrumb->updateContext(ctxResolver->currentContext());
+
     stopSpinTimer = new QTimer(this);
     connect(stopSpinTimer, &QTimer::timeout, this, &View3DInventor::stopAnimating);
 
@@ -935,6 +950,17 @@ void View3DInventor::contextMenuEvent(QContextMenuEvent* e)
     MDIView::contextMenuEvent(e);
 }
 
+bool View3DInventor::eventFilter(QObject* obj, QEvent* ev)
+{
+    if (obj == _viewer->getWidget() && ev->type() == QEvent::Resize) {
+        // Keep breadcrumb at top-left after viewport resize
+        if (_breadcrumb) {
+            _breadcrumb->raise();
+        }
+    }
+    return MDIView::eventFilter(obj, ev);
+}
+
 void View3DInventor::customEvent(QEvent* e)
 {
     if (e->type() == QEvent::User) {

src/Gui/View3DInventor.h

@@ -40,6 +40,7 @@ class QStackedWidget;
 namespace Gui
 {
 
+class BreadcrumbToolBar;
 class Document;
 class View3DInventorViewer;
 class View3DPy;
@@ -155,11 +156,13 @@ protected:
     void keyPressEvent(QKeyEvent* e) override;
     void keyReleaseEvent(QKeyEvent* e) override;
     void focusInEvent(QFocusEvent* e) override;
+    bool eventFilter(QObject* obj, QEvent* ev) override;
     void customEvent(QEvent* e) override;
     void contextMenuEvent(QContextMenuEvent* e) override;
 
 private:
     View3DInventorViewer* _viewer;
+    BreadcrumbToolBar* _breadcrumb;
     PyObject* _viewerPy;
     QTimer* stopSpinTimer;
     QStackedWidget* stack;