ui: separated GraphView style settings into class GraphViewStyle

This change adds the class GraphViewStyle that holds all values for defining the style of Nodes and Edges in the Graph.
The GraphViewStyleImpl interface and the QtGraphViewStyleImpl implementation are used to request Qt specific metrics,
like the charwidth of used fonts.

This change includes the following fixes:
* aggregation number always in the middle between nodes
* darker color for aggregation edge
* split off QGraphicsLineItem implementations from QtGraphEdge
* fixed some colors in color scheme

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src/lib/component/view/GraphViewStyle.h

@@ -0,0 +1,103 @@
+#ifndef GRAPH_VIEW_STYLE_H
+#define GRAPH_VIEW_STYLE_H
+
+#include <map>
+#include <memory>
+
+#include "component/view/graphElements/GraphNode.h"
+#include "component/view/GraphViewStyleImpl.h"
+#include "data/graph/Node.h"
+
+class GraphViewStyle
+{
+public:
+	struct NodeMargins
+	{
+		NodeMargins();
+
+		int left;
+		int right;
+
+		int top;
+		int bottom;
+
+		int spacingX;
+		int spacingY;
+
+		int minWidth;
+		float charWidth;
+	};
+
+	struct NodeStyle
+	{
+		NodeStyle();
+
+		std::string color;
+
+		std::string shadowColor;
+		int shadowBlurRadius;
+
+		int cornerRadius;
+
+		float borderWidth;
+		std::string borderColor;
+		bool borderDashed;
+
+		std::string fontName;
+		size_t fontSize;
+		bool fontBold;
+
+		Vec2i textOffset;
+
+		bool undefinedPattern;
+	};
+
+	struct EdgeStyle
+	{
+		EdgeStyle();
+
+		std::string color;
+
+		float width;
+		int zValue;
+
+		bool isStraight;
+
+		int arrowLength;
+		int arrowWidth;
+		bool arrowClosed;
+
+		int cornerRadius;
+		int verticalOffset;
+
+		Vec2i originOffset;
+		Vec2i targetOffset;
+	};
+
+	static std::shared_ptr<GraphViewStyleImpl> getImpl();
+	static void setImpl(std::shared_ptr<GraphViewStyleImpl> impl);
+
+	static float getCharWidthForNodeType(Node::NodeType type);
+
+	static size_t getFontSizeForNodeType(Node::NodeType type);
+	static size_t getFontSizeOfAccessNode();
+	static size_t getFontSizeOfNumber();
+
+	static std::string getFontNameForNodeType(Node::NodeType type);
+	static std::string getFontNameOfAccessNode();
+	static std::string getFontNameOfNumber();
+
+	static NodeMargins getMarginsForNodeType(Node::NodeType type, bool hasChildren);
+	static NodeMargins getMarginsOfAccessNode(bool expanded, size_t subNodeCount, size_t invisibleSubNodeCount);
+
+	static NodeStyle getStyleForNodeType(Node::NodeType type, bool isActive, bool isFocused, bool hasChildren);
+	static NodeStyle getStyleOfAccessNode();
+
+	static EdgeStyle getStyleForEdgeType(Edge::EdgeType type, bool isActive, bool isFocused);
+
+private:
+	static std::map<Node::NodeType, float> s_charWidths;
+	static std::shared_ptr<GraphViewStyleImpl> s_impl;
+};
+
+#endif // GRAPH_VIEW_STYLE_H