#5382: Add PatchControlIterator class

radiantcore/patch/algorithm/PatchIterators.h

@@ -0,0 +1,155 @@
+#pragma once
+
+#include "ipatch.h"
+#include <fmt/format.h>
+
+namespace patch
+{
+
+/**
+ * Forward iterator used to traverse the control points of a patch.
+ * The visited points, stride or ordering are defined by the forward function
+ * object passed to the constructor.
+ *
+ * Each iterator instance refers to a single control of the patch, defined
+ * by the row and col indices. An iterator whose coordinates are out of bounds
+ * will return isValid() == false, throwing exceptions when dereferenced.
+ *
+ * The state of the iterator is protected allowing subclasses to access
+ * it in their forward function implementation.
+ */
+class PatchControlIterator
+{
+public:
+    // The function object implementing the move-forward logic of this iterator
+    using Forwarder = std::function<void(PatchControlIterator&)>;
+
+protected:
+    IPatch& _patch;
+
+    // Using signed indices to allow out-of-bounds iterators
+    int _row;
+    int _col;
+
+    // Moves this iterator forward by one step
+    Forwarder _forward;
+
+protected:
+    PatchControlIterator(IPatch& patch, int row, int col, Forwarder forward) :
+        _patch(patch),
+        _row(row),
+        _col(col),
+        _forward(forward)
+    {}
+
+    PatchControlIterator(const PatchControlIterator& other) = default;
+    PatchControlIterator& operator=(const PatchControlIterator& other) = default;
+
+public:
+    // Post-increment i++
+    PatchControlIterator operator++(int)
+    {
+        PatchControlIterator previous = *this;
+        ++(*this);
+        return previous;
+    }
+
+    // Pre-increment ++i
+    PatchControlIterator& operator++()
+    {
+        // Call the logic moving our iterator forward by one step
+        _forward(*this);
+
+        return *this;
+    }
+
+    PatchControl& operator*()
+    {
+        throwIfOutOfBounds();
+        return _patch.ctrlAt(static_cast<std::size_t>(_row), static_cast<std::size_t>(_col));
+    }
+
+    const PatchControl& operator*() const
+    {
+        throwIfOutOfBounds();
+        return _patch.ctrlAt(_row, _col);
+    }
+
+    PatchControl* operator->()
+    {
+        return &**this;
+    }
+
+    const PatchControl* operator->() const
+    {
+        return &**this;
+    }
+
+    bool isValid() const
+    {
+        return _col >= 0 && _row >= 0 &&
+                _col < static_cast<int>(_patch.getWidth()) &&
+                _row < static_cast<int>(_patch.getHeight());
+    }
+
+    // Interface to set or reset the iterator coordinates
+    int getRow() const
+    {
+        return _row;
+    }
+
+    int getColumn() const
+    {
+        return _col;
+    }
+
+    void set(int row, int col)
+    {
+        _row = row;
+        _col = col;
+    }
+
+private:
+    void throwIfOutOfBounds() const
+    {
+        // Dereferencing an out-of-bounds iterator?
+        if (!isValid())
+        {
+            throw std::runtime_error(fmt::format("Iterator (row={0},col={1}) is out of bounds", _row, _col));
+        }
+    }
+};
+
+// An iterator traversing a single row of a patch
+class PatchRowIterator :
+    public PatchControlIterator
+{
+public:
+    PatchRowIterator(IPatch& patch, std::size_t row) :
+        PatchControlIterator(patch, static_cast<int>(row), 0, moveToNextCol)
+    {}
+
+private:
+    static void moveToNextCol(PatchControlIterator& it)
+    {
+        it.set(it.getRow(), it.getColumn() + 1);
+    }
+};
+
+// An iterator traversing a single column of a patch
+class PatchColumnIterator :
+    public PatchControlIterator
+{
+public:
+    PatchColumnIterator(IPatch& patch, std::size_t col) :
+        PatchControlIterator(patch, 0, static_cast<int>(col), moveToNextRow)
+    {}
+
+private:
+    static void moveToNextRow(PatchControlIterator& it)
+    {
+        it.set(it.getRow() + 1, it.getColumn());
+    }
+};
+
+}

tools/msvc/DarkRadiantCore.vcxproj

@@ -900,6 +900,7 @@
     <ClInclude Include="..\..\radiantcore\particles\RenderableParticleStage.h" />
     <ClInclude Include="..\..\radiantcore\particles\StageDef.h" />
     <ClInclude Include="..\..\radiantcore\patch\algorithm\General.h" />
+    <ClInclude Include="..\..\radiantcore\patch\algorithm\PatchIterators.h" />
     <ClInclude Include="..\..\radiantcore\patch\algorithm\Prefab.h" />
     <ClInclude Include="..\..\radiantcore\patch\Patch.h" />
     <ClInclude Include="..\..\radiantcore\patch\PatchConstants.h" />

tools/msvc/DarkRadiantCore.vcxproj.filters

@@ -2061,5 +2061,8 @@
     <ClInclude Include="..\..\radiantcore\rendersystem\OpenGLModule.h">
       <Filter>src\rendersystem</Filter>
     </ClInclude>
+    <ClInclude Include="..\..\radiantcore\patch\algorithm\PatchIterators.h">
+      <Filter>src\patch\algorithm</Filter>
+    </ClInclude>
   </ItemGroup>
 </Project>