#5532: Introduce an extended IEditableShaderLayer interface.

Just returning a const IShaderLayer reference for non-edit scenarios turns out to be impractical, since the render passes need to evaluate time-dependent expressions and update the stage's registers, requiring non-const access to the stages. The Material itself needs to know when it's being modified, so I went for intruducing a separate Material::getEditableLayer() method that is taking care of the backup clone as soon as it's called. This way it's possible to inspect and render a material without implicitly marking it as modified.

include/ishaderlayer.h

@@ -365,9 +365,6 @@ class IShaderLayer
     // The map expression used to generate/define the texture of this stage
     virtual shaders::IMapExpression::Ptr getMapExpression() const = 0;
 
-    // Update the "map" expression of this stage
-    virtual void setMapExpressionFromString(const std::string& expression) = 0;
-
     // Parser information, to reconstruct the use of certain keywords
     virtual int getParseFlags() const = 0;
 };
@@ -378,3 +375,15 @@ class IShaderLayer
  */
 typedef std::vector<IShaderLayer::Ptr> IShaderLayerVector;
 
+// Interface extension to IShaderLayer, offering editing functions
+class IEditableShaderLayer :
+    public IShaderLayer
+{
+public:
+    using Ptr = std::shared_ptr<IEditableShaderLayer>;
+
+    virtual ~IEditableShaderLayer() {}
+
+    // Update the "map" expression of this stage
+    virtual void setMapExpressionFromString(const std::string& expression) = 0;
+};

include/ishaders.h

@@ -319,6 +319,10 @@ class Material
      */
     virtual const IShaderLayerVector& getAllLayers() const = 0;
 
+    // Returns the edit interface for the given shader layer. Calling this method
+    // will immediately mark this Material as modified.
+    virtual const IEditableShaderLayer::Ptr& getEditableLayer(std::size_t index) = 0;
+
     /// Return the 2D light falloff texture, if this is a light shader
     virtual TexturePtr lightFalloffImage() = 0;
 

radiantcore/shaders/CShader.cpp

@@ -297,18 +297,27 @@ IShaderLayer* CShader::firstLayer() const
 {
 	if (_layers.empty())
 	{
-		return NULL;
+		return nullptr;
 	}
 
 	return _layers.front().get();
 }
 
-// Get all layers
 const IShaderLayerVector& CShader::getAllLayers() const
 {
     return _layers;
 }
 
+const IEditableShaderLayer::Ptr& CShader::getEditableLayer(std::size_t index)
+{
+    ensureTemplateCopy();
+
+    const auto& layers = _template->getLayers();
+    assert(index >= 0 && index < layers.size());
+
+    return layers[index];
+}
+
 /* Required Material light type predicates */
 
 bool CShader::isAmbientLight() const {

radiantcore/shaders/CShader.h

@@ -93,6 +93,7 @@ class CShader final :
 	bool isVisible() const override;
 	void setVisible(bool visible) override;
     const IShaderLayerVector& getAllLayers() const;
+    const IEditableShaderLayer::Ptr& getEditableLayer(std::size_t index) override;
 
     IMapExpression::Ptr getLightFalloffExpression() override;
 	IMapExpression::Ptr getLightFalloffCubeMapExpression() override;

radiantcore/shaders/Doom3ShaderLayer.h

@@ -19,7 +19,7 @@ class ShaderTemplate;
  * Implementation of IShaderLayer for Doom 3 shaders.
  */
 class Doom3ShaderLayer : 
-    public IShaderLayer
+    public IEditableShaderLayer
 {
 private:
     // The owning material template