#92: extract the main rendering code to the RenderElement method

src/WpfMath/Box.cs

@@ -1,6 +1,5 @@
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
-using System.Windows;
 using System.Windows.Media;
 using WpfMath.Rendering;
 
@@ -87,30 +86,9 @@ public double Shift
             set;
         }
 
-        /// <summary>
-        /// Draws the box into a <see cref="DrawingContext"/> while providing guidelines for WPF render to snap
-        /// the box boundaries onto the device pixel grid.
-        /// </summary>
-        public void DrawWithGuidelines(DrawingContext drawingContext, double scale, double x, double y)
-        {
-            var guidelines = new GuidelineSet
-            {
-                GuidelinesX = { scale * x, scale * (x + TotalWidth) },
-                GuidelinesY = { scale * y, scale * (y + TotalHeight) }
-            };
-            drawingContext.PushGuidelineSet(guidelines);
-
-            DrawBackground(drawingContext, scale, x, y);
-            Draw(drawingContext, scale, x, y);
-
-            drawingContext.Pop();
-        }
-
-        public abstract void Draw(DrawingContext drawingContext, double scale, double x, double y);
-
+        // TODO[F]: Remove this method and replace with GeometryRenderer.
         public abstract void RenderGeometry(GeometryGroup geometry, double scale, double x, double y);
 
-        // TODO[F]: Make it call DrawWithGuidelines before every render.
         public abstract void RenderTo(IElementRenderer renderer, double x, double y);
 
         public virtual void Add(Box box)
@@ -124,19 +102,5 @@ public virtual void Add(int position, Box box)
         }
 
         public abstract int GetLastFontId();
-
-        private void DrawBackground(DrawingContext drawingContext, double scale, double x, double y)
-        {
-            if (Background != null)
-            {
-                // Fill background of box with color:
-                drawingContext.DrawRectangle(
-                    Background,
-                    null,
-                    new Rect(scale * x, scale * (y - Height),
-                    scale * TotalWidth,
-                    scale * TotalHeight));
-            }
-        }
     }
 }

src/WpfMath/CharBox.cs

@@ -34,14 +34,6 @@ private GlyphRun GetGlyphRun(double scale, double x, double y)
 
         }
 
-        public override void Draw(DrawingContext drawingContext, double scale, double x, double y)
-        {
-            GlyphRun glyphRun = GetGlyphRun(scale, x, y);
-
-            // Draw character at given position.
-            drawingContext.DrawGlyphRun(this.Foreground ?? Brushes.Black, glyphRun);
-        }
-
         public override void RenderGeometry(GeometryGroup geometry, double scale, double x, double y)
         {
             GlyphRun glyphRun = GetGlyphRun(scale, x, y);

src/WpfMath/GlueBox.cs

@@ -25,10 +25,6 @@ public double Shrink
             private set;
         }
 
-        public override void Draw(DrawingContext drawingContext, double scale, double x, double y)
-        {
-        }
-
         public override void RenderGeometry(GeometryGroup geometry, double scale, double x, double y)
         {
         }

src/WpfMath/HorizontalBox.cs

@@ -59,16 +59,6 @@ public override void Add(Box box)
             this.Italic = Math.Max((this.Children.Count == 0 ? double.NegativeInfinity : Italic), box.Italic);
         }
 
-        public override void Draw(DrawingContext drawingContext, double scale, double x, double y)
-        {
-            var curX = x;
-            foreach (var box in Children)
-            {
-                box.DrawWithGuidelines(drawingContext, scale, curX, y + box.Shift);
-                curX += box.Width;
-            }
-        }
-
         public override void RenderGeometry(GeometryGroup geometry, double scale, double x, double y)
         {
             var curX = x;
@@ -84,7 +74,7 @@ public override void RenderTo(IElementRenderer renderer, double x, double y)
             var curX = x;
             foreach (var box in Children)
             {
-                box.RenderTo(renderer, curX, y + box.Shift);
+                renderer.RenderElement(box, curX, y + box.Shift);
                 curX += box.Width;
             }
         }

src/WpfMath/HorizontalRule.cs

@@ -20,12 +20,6 @@ public HorizontalRule(TexEnvironment environment, double thickness, double width
             this.Background = environment.Background;	//Not strictly necessary
         }
 
-        public override void Draw(DrawingContext drawingContext, double scale, double x, double y)
-        {
-            drawingContext.DrawRectangle(this.Foreground ?? Brushes.Black, null, new Rect(
-                x * scale, (y - this.Height) * scale, this.Width * scale, this.Height * scale));
-        }
-
         public override void RenderGeometry(GeometryGroup geometry, double scale, double x, double y)
         {
             RectangleGeometry rectangleGeometry = new RectangleGeometry(new Rect(

src/WpfMath/OverUnderBox.cs

@@ -55,48 +55,6 @@ public bool Over
             private set;
         }
 
-        public override void Draw(DrawingContext drawingContext, double scale, double x, double y)
-        {
-            this.BaseBox.DrawWithGuidelines(drawingContext, scale, x, y);
-
-            if (this.Over)
-            {
-                // Draw delimeter and script boxes over base box.
-                var centerY = y - this.BaseBox.Height - this.DelimeterBox.Width;
-                var translationX = x + this.DelimeterBox.Width / 2;
-                var translationY = centerY + this.DelimeterBox.Width / 2;
-
-                drawingContext.PushTransform(new TranslateTransform(translationX * scale, translationY * scale));
-                drawingContext.PushTransform(new RotateTransform(90));
-                this.DelimeterBox.DrawWithGuidelines(drawingContext, scale, -this.DelimeterBox.Width / 2,
-                    -this.DelimeterBox.Depth + this.DelimeterBox.Width / 2);
-                drawingContext.Pop();
-                drawingContext.Pop();
-
-                // Draw script box as superscript.
-                if (this.ScriptBox != null)
-                    this.ScriptBox.DrawWithGuidelines(drawingContext, scale, x, centerY - this.Kern - this.ScriptBox.Depth);
-            }
-            else
-            {
-                // Draw delimeter and script boxes under base box.
-                var centerY = y + this.BaseBox.Depth + this.DelimeterBox.Width;
-                var translationX = x + this.DelimeterBox.Width / 2;
-                var translationY = centerY - this.DelimeterBox.Width / 2;
-
-                drawingContext.PushTransform(new TranslateTransform(translationX * scale, translationY * scale));
-                drawingContext.PushTransform(new RotateTransform(90));
-                this.DelimeterBox.DrawWithGuidelines(drawingContext, scale, -this.DelimeterBox.Width / 2,
-                    -this.DelimeterBox.Depth + this.DelimeterBox.Width / 2);
-                drawingContext.Pop();
-                drawingContext.Pop();
-
-                // Draw script box as subscript.
-                ScriptBox?.DrawWithGuidelines(drawingContext, scale, x, centerY + Kern + ScriptBox.Height);
-            }
-
-        }
-
         public override void RenderGeometry(GeometryGroup geometry, double scale, double x, double y)
         {
             GeometryGroup group = new GeometryGroup();
@@ -137,7 +95,7 @@ public override void RenderGeometry(GeometryGroup geometry, double scale, double
 
         public override void RenderTo(IElementRenderer renderer, double x, double y)
         {
-            BaseBox.RenderTo(renderer, x, y);
+            renderer.RenderElement(BaseBox, x, y);
 
             if (Over)
             {
@@ -159,7 +117,10 @@ public override void RenderTo(IElementRenderer renderer, double x, double y)
                     -DelimeterBox.Depth + DelimeterBox.Width / 2);
 
                 // Draw script box as superscript.
-                ScriptBox?.RenderTo(renderer, x, centerY - Kern - ScriptBox.Depth);
+                if (ScriptBox != null)
+                {
+                    renderer.RenderElement(ScriptBox, x, centerY - Kern - ScriptBox.Depth);
+                }
             }
             else
             {
@@ -184,7 +145,10 @@ public override void RenderTo(IElementRenderer renderer, double x, double y)
                     -DelimeterBox.Depth + DelimeterBox.Width / 2);
 
                 // Draw script box as subscript.
-                ScriptBox?.RenderTo(renderer, x, centerY + Kern + ScriptBox.Height);
+                if (ScriptBox != null)
+                {
+                    renderer.RenderElement(ScriptBox, x, centerY + Kern + ScriptBox.Height);
+                }
             }
         }
 

src/WpfMath/Rendering/IElementRenderer.cs

@@ -7,6 +7,13 @@ namespace WpfMath.Rendering
     /// <summary>Renderer interface for WPF-Math elements.</summary>
     public interface IElementRenderer
     {
+        /// <summary>Renders a <see cref="Box"/> to the renderer drawing context.</summary>
+        /// <param name="box">The element that should be rendered.</param>
+        /// <param name="x">An X coordinate of the top left corner.</param>
+        /// <param name="y">An Y coordinate of the top left corner.</param>
+        /// <remarks>Should be called for every element of the formula (including nested ones).</remarks>
+        void RenderElement(Box box, double x, double y);
+
         /// <summary>Renders a glyph run (e.g. a character).</summary>
         /// <param name="scaledGlyphFactory">Function to generate a glyph run for the chosen scale.</param>
         /// <param name="x">An X coordinate of the top left corner.</param>

src/WpfMath/Rendering/WpfElementRenderer.cs

@@ -17,6 +17,17 @@ public WpfElementRenderer(DrawingContext drawingContext, double scale)
             _scale = scale;
         }
 
+        public void RenderElement(Box box, double x, double y)
+        {
+            var guidelines = GenerateGuidelines(box, x, y);
+            _drawingContext.PushGuidelineSet(guidelines);
+
+            RenderBackground(box, x, y);
+            box.RenderTo(this, x, y);
+
+            _drawingContext.Pop();
+        }
+
         public void RenderGlyphRun(Func<double, GlyphRun> scaledGlyphFactory, double x, double y, Brush foreground)
         {
             var glyphRun = scaledGlyphFactory(_scale);
@@ -37,14 +48,37 @@ public void RenderTransformed(Box box, Transform[] transforms, double x, double
                 _drawingContext.PushTransform(transform);
             }
 
-            box.RenderTo(this, x, y);
+            RenderElement(box, x, y);
 
             for (var i = 0; i < scaledTransforms.Count; ++i)
             {
                 _drawingContext.Pop();
             }
         }
 
+        private void RenderBackground(Box box, double x, double y)
+        {
+            if (box.Background != null)
+            {
+                // Fill background of box with color:
+                _drawingContext.DrawRectangle(
+                    box.Background,
+                    null,
+                    new Rect(_scale * x, _scale * (y - box.Height),
+                        _scale * box.TotalWidth,
+                        _scale * box.TotalHeight));
+            }
+        }
+
+        /// <summary>
+        /// Genetates the guidelines for WPF render to snap the box boundaries onto the device pixel grid.
+        /// </summary>
+        private GuidelineSet GenerateGuidelines(Box box, double x, double y) => new GuidelineSet
+        {
+            GuidelinesX = {_scale * x, _scale * (x + box.TotalWidth)},
+            GuidelinesY = {_scale * y, _scale * (y + box.TotalHeight)}
+        };
+
         private Rect ScaleRectangle(Rect rectangle) =>
             new Rect(rectangle.X * _scale, rectangle.Y * _scale, rectangle.Width * _scale, rectangle.Height * _scale);
 

src/WpfMath/StrutBox.cs

@@ -21,10 +21,6 @@ public StrutBox(double width, double height, double depth, double shift)
             this.Shift = shift;
         }
 
-        public override void Draw(DrawingContext drawingContext, double scale, double x, double y)
-        {
-        }
-
         public override void RenderGeometry(GeometryGroup geometry, double scale, double x, double y)
         {
         }

src/WpfMath/TexRenderer.cs

@@ -66,7 +66,7 @@ public BitmapSource RenderToBitmap(double x, double y)
         public void Render(DrawingContext drawingContext, double x, double y)
         {
             var renderer = new WpfElementRenderer(drawingContext, Scale);
-            Box.RenderTo(renderer, x / Scale, y / Scale + Box.Height);
+            renderer.RenderElement(Box, x / Scale, y / Scale + Box.Height);
         }
     }
 }

src/WpfMath/VerticalBox.cs

@@ -78,18 +78,6 @@ private void RecalculateWidth(Box box)
             this.Width = rightMostPos - leftMostPos;
         }
 
-        public override void Draw(DrawingContext drawingContext, double scale, double x, double y)
-        {
-            var curY = y - Height;
-            foreach (var child in this.Children)
-            {
-                curY += child.Height;
-
-                child.DrawWithGuidelines(drawingContext, scale, x + child.Shift - leftMostPos, curY);
-                curY += child.Depth;
-            }
-        }
-
         public override void RenderGeometry(GeometryGroup geometry, double scale, double x, double y)
         {
             var curY = y - Height;
@@ -107,7 +95,7 @@ public override void RenderTo(IElementRenderer renderer, double x, double y)
             foreach (var child in Children)
             {
                 curY += child.Height;
-                child.RenderTo(renderer, x + child.Shift - leftMostPos, curY);
+                renderer.RenderElement(child, x + child.Shift - leftMostPos, curY);
                 curY += child.Depth;
             }
         }