Base: Add Base::ProgressIndicator for OCCT progress reporting

Introduce a new `ProgressIndicator` base class
(`ProgressIndicator.h`/`.cpp`) with a singleton-managed, no-op default
implementation matching OCCT’s `Message_ProgressIndicator` interface.
Update `CMakeLists.txt` to include the new sources.

src/Base/CMakeLists.txt

@@ -205,6 +205,7 @@ SET(FreeCADBase_CPP_SRCS
     Placement.cpp
     PlacementPyImp.cpp
     PrecisionPyImp.cpp
+    ProgressIndicator.cpp
     ProgressIndicatorPy.cpp
     PyExport.cpp
     PyObjectBase.cpp
@@ -271,6 +272,7 @@ SET(FreeCADBase_HPP_SRCS
     Placement.h
     Precision.h
     ProgressIndicatorPy.h
+    ProgressIndicator.h
     PyExport.h
     PyObjectBase.h
     PyWrapParseTupleAndKeywords.h

src/Base/ProgressIndicator.cpp

@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: LGPL-2.1-or-later
+/***************************************************************************
+ *   Copyright (c) 2025 James Stanley <james@incoherency.co.uk>            *
+ *                                                                         *
+ *   This file is part of FreeCAD.                                         *
+ *                                                                         *
+ *   FreeCAD is free software: you can redistribute it and/or modify it    *
+ *   under the terms of the GNU Lesser General Public License as           *
+ *   published by the Free Software Foundation, either version 2.1 of the  *
+ *   License, or (at your option) any later version.                       *
+ *                                                                         *
+ *   FreeCAD is distributed in the hope that it will be useful, but        *
+ *   WITHOUT ANY WARRANTY; without even the implied warranty of            *
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU      *
+ *   Lesser General Public License for more details.                       *
+ *                                                                         *
+ *   You should have received a copy of the GNU Lesser General Public      *
+ *   License along with FreeCAD. If not, see                               *
+ *   <https://www.gnu.org/licenses/>.                                      *
+ *                                                                         *
+ **************************************************************************/
+
+#include "ProgressIndicator.h"
+
+namespace Base
+{
+
+ProgressIndicator::ProgressIndicator() = default;
+ProgressIndicator::ProgressIndicator(const ProgressIndicator&) = default;
+ProgressIndicator& ProgressIndicator::operator=(const ProgressIndicator&) = default;
+ProgressIndicator::~ProgressIndicator() = default;
+
+}  // namespace Base

src/Base/ProgressIndicator.h

@@ -0,0 +1,97 @@
+// SPDX-License-Identifier: LGPL-2.1-or-later
+/***************************************************************************
+ *   Copyright (c) 2025 James Stanley <james@incoherency.co.uk>            *
+ *                                                                         *
+ *   This file is part of FreeCAD.                                         *
+ *                                                                         *
+ *   FreeCAD is free software: you can redistribute it and/or modify it    *
+ *   under the terms of the GNU Lesser General Public License as           *
+ *   published by the Free Software Foundation, either version 2.1 of the  *
+ *   License, or (at your option) any later version.                       *
+ *                                                                         *
+ *   FreeCAD is distributed in the hope that it will be useful, but        *
+ *   WITHOUT ANY WARRANTY; without even the implied warranty of            *
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU      *
+ *   Lesser General Public License for more details.                       *
+ *                                                                         *
+ *   You should have received a copy of the GNU Lesser General Public      *
+ *   License along with FreeCAD. If not, see                               *
+ *   <https://www.gnu.org/licenses/>.                                      *
+ *                                                                         *
+ **************************************************************************/
+
+#ifndef BASE_PROGRESSINDICATOR_H
+#define BASE_PROGRESSINDICATOR_H
+
+#include "FCGlobal.h"
+
+namespace Base
+{
+
+/**
+ * @class ProgressIndicator
+ * @brief Base interface for reporting and controlling long-running operations.
+ *
+ * This abstract base class provides a uniform way to:
+ *   - Display progress updates via @c show().
+ *   - Query whether the user has requested cancellation via @c userBreak().
+ *
+ * By default:
+ *   - @c userBreak() returns false (no cancellation).
+ *   - @c show() is a no-op.
+ *
+ * Derived classes should override these methods to integrate with
+ * specific UI frameworks or console output.
+ */
+class BaseExport ProgressIndicator
+{
+public:
+    /**
+     * @brief Flags to control behavior of the show() update.
+     */
+    enum class ShowFlags
+    {
+        None = 0,  ///< Default behavior; update only if significant progress.
+        Force = 1  ///< Force update regardless of progress threshold.
+    };
+
+    ProgressIndicator();
+    ProgressIndicator(const ProgressIndicator&);
+    ProgressIndicator(ProgressIndicator&&) = delete;
+    ProgressIndicator& operator=(const ProgressIndicator&);
+    ProgressIndicator& operator=(ProgressIndicator&&) = delete;
+    virtual ~ProgressIndicator();
+
+    /**
+     * @brief Check if the user has requested to abort the operation.
+     *
+     * Override to implement cancellation logic.
+     *
+     * @return @c true if the user requested a break, @c false otherwise.
+     */
+    virtual bool userBreak()
+    {
+        return false;
+    }
+
+    /**
+     * @brief Update the progress display.
+     *
+     * This method is called whenever the progress position changes.
+     *
+     * The parameter `position` is a normalized progress value:
+     *   - Range [0.0, 1.0] for determinate progress (e.g., 0.57 for 57% complete).
+     *   - A value of -1.0 indicates infinite (indeterminate) progress.
+     *
+     * @param position Normalized progress value or -1.0 for infinite progress.
+     * @param isForce  If true, indicates a forced update even if the change threshold (≈1%) hasn’t
+     * been met.
+     */
+    virtual void show([[maybe_unused]] float position,
+                      [[maybe_unused]] ShowFlags flags = ShowFlags::None)
+    {}
+};
+
+}  // namespace Base
+
+#endif