Extract ScopedIncrementor into utility

Move the helper class ScopedIncrementor into kdevplatform/util, because
it has other uses than just in the BreakpointModel.

Introduce a new class template NonNegative to assert that we don't
accidentally decrement the counter below zero. Convert the class
ScopedIncrementor into a class template that can operate with an
instance of NonNegative or any other integral type.

If a future use arises for being able to move a ScopedIncrementor guard
or construct it from an already incremented counter, such semantics can
be implemented later.

kdevplatform/debugger/breakpoint/breakpointmodel.cpp

@@ -77,7 +77,7 @@ class KDevelop::BreakpointModelPrivate
     ReloadState reloadState = ReloadState::Idle;
     /// Non-zero while KDevelop code is adding or removing a document mark.
     /// This allows to react to user-driven mark changes without getting confused by our own code changes.
-    int inhibitMarkChange = 0;
+    NonNegative<> inhibitMarkChange;
     QList<Breakpoint*> breakpoints;
     /// FIXME: this is just an ugly workaround to not leak deleted breakpoints
     ///        a real fix would make sure that we actually delete breakpoints
@@ -688,7 +688,7 @@ void BreakpointModel::reportChange(Breakpoint* breakpoint, Breakpoint::Column co
     scheduleSave();
 }
 
-ScopedIncrementor BreakpointModel::markChangeGuard()
+ScopedIncrementor<> BreakpointModel::markChangeGuard()
 {
     Q_D(BreakpointModel);
 

kdevplatform/debugger/breakpoint/breakpointmodel.h

@@ -13,6 +13,7 @@
 #include "breakpoint.h"
 
 #include <util/namespacedoperatorbitwiseorworkaroundqtbug.h>
+#include <util/scopedincrementor.h>
 
 #include <KTextEditor/Document>
 
@@ -31,23 +32,6 @@ class IDocument;
 class Breakpoint;
 class BreakpointModelPrivate;
 
-class ScopedIncrementor
-{
-    int& m_value;
-
-public:
-    explicit ScopedIncrementor(int& value)
-        : m_value(value)
-    {
-        ++m_value;
-    }
-    ~ScopedIncrementor()
-    {
-        --m_value;
-    }
-    Q_DISABLE_COPY_MOVE(ScopedIncrementor)
-};
-
 class KDEVPLATFORMDEBUGGER_EXPORT BreakpointModel : public QAbstractTableModel
 {
     Q_OBJECT
@@ -197,7 +181,7 @@ private Q_SLOTS:
     /**
      * Call this function and keep the returned guard object alive while adding or removing document marks.
      */
-    ScopedIncrementor markChangeGuard();
+    ScopedIncrementor<> markChangeGuard();
 
     /**
      * Remove all breakpoint marks from @p document.

kdevplatform/util/CMakeLists.txt

@@ -101,6 +101,7 @@ install( FILES
     projecttestjob.h
     widgetcolorizer.h
     path.h
+    scopedincrementor.h
     stack.h
     stringviewhelpers.h
     texteditorhelpers.h

kdevplatform/util/scopedincrementor.h

@@ -0,0 +1,64 @@
+/*
+    SPDX-FileCopyrightText: 2024 Jarmo Tiitto <[email protected]>
+
+    SPDX-License-Identifier: LGPL-2.1-or-later
+*/
+
+#ifndef KDEVPLATFORM_SCOPEDINCREMENTOR_H
+#define KDEVPLATFORM_SCOPEDINCREMENTOR_H
+
+#include <QtAssert>
+#include <QtClassHelperMacros>
+
+namespace KDevelop {
+
+template<typename T = int>
+class NonNegative
+{
+public:
+    NonNegative& operator++()
+    {
+        ++m_value;
+        return *this;
+    }
+
+    NonNegative& operator--()
+    {
+        Q_ASSERT(m_value);
+        --m_value;
+        return *this;
+    }
+
+    operator bool() const
+    {
+        return m_value;
+    }
+
+private:
+    T m_value = 0;
+};
+
+template<typename T = NonNegative<int>>
+class ScopedIncrementor
+{
+public:
+    explicit ScopedIncrementor(T& value)
+        : m_value(value)
+    {
+        ++m_value;
+    }
+
+    ~ScopedIncrementor()
+    {
+        --m_value;
+    }
+
+    Q_DISABLE_COPY_MOVE(ScopedIncrementor)
+
+private:
+    T& m_value;
+};
+
+}
+
+#endif // KDEVPLATFORM_SCOPEDINCREMENTOR_H