Balanced linespacing above and below text for better highlighting look. (#872)

Author: Jugen

richtextfx/src/main/java/org/fxmisc/richtext/GenericStyledArea.java

@@ -1187,7 +1187,8 @@ public void setLineHighlighterOn( boolean show )
                 {
                     int p = getCurrentParagraph();
                     int start = getCurrentLineStartInParargraph();
-                    int end = getCurrentLineEndInParargraph() + 1; // +1 for empty lines
+                    int end = getCurrentLineEndInParargraph();
+                    if (end == 0) end++;// +1 for empty lines
                     lineHighlighter.selectRange( p, start, p, end );
                 }
             };

richtextfx/src/main/java/org/fxmisc/richtext/ParagraphBox.java

@@ -95,9 +95,6 @@ public final ObservableMap<Selection<PS, SEG, S>, SelectionPath> selectionsPrope
         this.text = new ParagraphText<>(par, nodeFactory);
         applyParagraphStyle.accept(this.text, par.getParagraphStyle());
 
-        // Apply line-spacing (in a paragraph) to between paragraphs as well. Can be overriden with -fx-padding CSS.
-        text.lineSpacingProperty().addListener( (ob,ov,nv) -> setPadding( new Insets( 0, 0, nv.doubleValue(), 0 ) ) );
-        
         // start at -1 so that the first time it is displayed, the caret at pos 0 is not
         // accidentally removed from its parent and moved to this node's ParagraphText
         // before this node gets updated to its real index and therefore removes
@@ -240,21 +237,20 @@ protected double computePrefWidth(double ignoredHeight) {
     protected double computePrefHeight(double width) {
         Insets insets = getInsets();
         double overhead = getGraphicPrefWidth() + insets.getLeft() + insets.getRight();
-        return text.prefHeight(width - overhead) + insets.getTop() + insets.getBottom();
+        return text.prefHeight(width - overhead) + insets.getTop() + insets.getBottom() + text.getLineSpacing();
     }
 
     @Override
-    protected
-    void layoutChildren() {
+    protected void layoutChildren() {
         Insets ins = getInsets();
         double w = getWidth() - ins.getLeft() - ins.getRight();
         double h = getHeight() - ins.getTop() - ins.getBottom();
         double graphicWidth = getGraphicPrefWidth();
+        double half = text.getLineSpacing() / 2.0;
 
-        text.resizeRelocate(graphicWidth + ins.getLeft(), ins.getTop(), w - graphicWidth, h);
+        text.resizeRelocate(graphicWidth + ins.getLeft(), ins.getTop() + half, w - graphicWidth, h - half);
 
-        graphic.ifPresent(g -> g.resizeRelocate(graphicOffset.get() + ins.getLeft(), ins.getTop(), graphicWidth, h + ins.getBottom()));
-        // h + ins.getBottom() so that there aren't gaps when -fx-line-spacing or -fx-padding is active.
+        graphic.ifPresent(g -> g.resizeRelocate(graphicOffset.get() + ins.getLeft(), ins.getTop(), graphicWidth, h));
     }
 
     double getGraphicPrefWidth() {

richtextfx/src/main/java/org/fxmisc/richtext/ParagraphText.java

@@ -361,7 +361,7 @@ private PathElement[] getRangeShapeSafely(int start, int end) {
             } else {
                 shape = getRangeShape(start, paragraph.length());
                 // Since this might be a wrapped multi-line paragraph,
-                // there may be multiple groups of (1 MoveTo, 3 LineTo objects) for each line:
+                // there may be multiple groups of (1 MoveTo, 4 LineTo objects) for each line:
                 // MoveTo(topLeft), LineTo(topRight), LineTo(bottomRight), LineTo(bottomLeft)
 
                 // We only need to adjust the top right and bottom right corners to extend to the
@@ -378,6 +378,22 @@ private PathElement[] getRangeShapeSafely(int start, int end) {
             }
         }
 
+        if ( getLineSpacing() > 0 ) {
+            double half = getLineSpacing() / 2.0;
+            for ( int g = 0; g < shape.length; g += 5 ) {
+                MoveTo tl = (MoveTo) shape[g];
+                tl.setY( tl.getY()-half );
+                LineTo tr = (LineTo) shape[g+1];
+                tr.setY( tl.getY() );
+                LineTo br = (LineTo) shape[g+2];
+                br.setY( br.getY()+half );
+                LineTo bl = (LineTo) shape[g+3];
+                bl.setY( br.getY() );
+                LineTo t2 = (LineTo) shape[g+4];
+                t2.setY( tl.getY() );
+            }
+        }
+
         if (getLineCount() > 1) {
             // adjust right corners of wrapped lines
             boolean wrappedAtEndPos = (end > 0 && getLineOfCharacter(end) > getLineOfCharacter(end - 1));