Resistors, capacitors, diodes, ICs, transistors and other PCB parts can be placed on the bottom of the board with the new 'Board Side' property; Gerber export puts their silkscreen on the bottom layer with the text mirrored

diylc/diylc-core/src/main/java/org/diylc/core/gerber/GerberExporter.java

@@ -162,13 +162,16 @@ public class GerberExporter {
       IGerberComponentSimple gerberComponentSimple = (IGerberComponentSimple) gerberComponent;
       GerberLayer layer = gerberComponentSimple.getGerberLayer();
       // components emit their top-side layer; a part mounted underneath goes to the bottom one
-      if (c instanceof IBoardSideComponent
-          && ((IBoardSideComponent) c).getBoardSide() == PCBLayer._1) {
+      boolean bottomSide = c instanceof IBoardSideComponent
+          && ((IBoardSideComponent) c).getBoardSide() == PCBLayer._1;
+      if (bottomSide) {
         layer = layer.flip();
       }
       g2d.startGerberOutput(layer, gerberComponentSimple.getGerberFunction(),
               gerberComponentSimple.isGerberNegative());
+      g2d.setMirrorText(bottomSide);
       c.draw(g2d, ComponentState.NORMAL, outlineMode, currentProject, g2d);
+      g2d.setMirrorText(false);
       g2d.stopGerberOutput();
     }
   }

diylc/diylc-core/src/main/java/org/diylc/core/gerber/GerberG2DWrapper.java

@@ -58,6 +58,7 @@ public class GerberG2DWrapper extends Graphics2D
   private double tolerance;
 
   private Rectangle2D boardRect;
+  private boolean mirrorText = false;
 
   public GerberG2DWrapper(Graphics2D graphics2d, String diylcVersion, Rectangle2D boardRect) {
     super();
@@ -154,6 +155,15 @@ public class GerberG2DWrapper extends Graphics2D
     return layerMap;
   }
 
+  /**
+   * Sets whether text is written mirrored, each string about its own centre. The output is in top
+   * view, so text on the bottom side has to be mirrored to read correctly once the board is turned
+   * over.
+   */
+  public void setMirrorText(boolean mirrorText) {
+    this.mirrorText = mirrorText;
+  }
+
   @Override
   public void draw(Shape s) {
     if (trackingGerber && !getColor().equals(Constants.TRANSPARENT_COLOR)) {
@@ -181,6 +191,10 @@ public class GerberG2DWrapper extends Graphics2D
     GlyphVector gv = font.createGlyphVector(graphics2d.getFontRenderContext(), str);
     
     AffineTransform translateInstance = AffineTransform.getTranslateInstance(x, y);
+    if (mirrorText) {
+      translateInstance.translate(gv.getLogicalBounds().getWidth(), 0);
+      translateInstance.scale(-1, 1);
+    }
 
     for (int i = 0; i < gv.getNumGlyphs(); i++) {
         Shape glyphShape = gv.getGlyphOutline(i);

diylc/diylc-core/src/test/java/org/diylc/core/gerber/GerberExporterTest.java

@@ -22,12 +22,17 @@
 package org.diylc.core.gerber;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
 
 import java.awt.Color;
+import java.awt.Font;
 import java.awt.Graphics2D;
+import java.awt.Shape;
 import java.awt.geom.Rectangle2D;
 import java.awt.image.BufferedImage;
+import java.util.ArrayList;
 import java.util.EnumSet;
+import java.util.List;
 
 import org.diylc.common.PCBLayer;
 import org.diylc.core.ComponentState;
@@ -74,6 +79,49 @@ public class GerberExporterTest {
     assertEquals(EnumSet.of(GerberLayer.SilkscreenTop), EnumSet.copyOf(g2d.getLayerMap().keySet()));
   }
 
+  @Test
+  public void testTopSideTextReadsLeftToRight() {
+    List<Rectangle2D> glyphs = drawText(PCBLayer._2);
+
+    assertTrue(glyphs.get(0).getMinX() < glyphs.get(1).getMinX());
+  }
+
+  @Test
+  public void testBottomSideTextIsMirrored() {
+    List<Rectangle2D> top = drawText(PCBLayer._2);
+    List<Rectangle2D> bottom = drawText(PCBLayer._1);
+
+    // seen from the top, the first letter of a bottom-side label is on the right
+    assertTrue(bottom.get(0).getMinX() > bottom.get(1).getMinX());
+    // mirrored about the centre of its layout box, so the text stays where it was; the glyphs'
+    // uneven side bearings move their drawn bounds by a pixel or so
+    assertEquals(union(top).getCenterX(), union(bottom).getCenterX(), 2);
+  }
+
+  private static List<Rectangle2D> drawText(PCBLayer side) {
+    List<Rectangle2D> glyphs = new ArrayList<Rectangle2D>();
+    BufferedImage img = new BufferedImage(100, 100, BufferedImage.TYPE_INT_ARGB);
+    Graphics2D graphics = img.createGraphics();
+    GerberG2DWrapper g2d =
+        new GerberG2DWrapper(graphics, "test", new Rectangle2D.Double(0, 0, 100, 100)) {
+          @Override
+          public void fillShape(Shape s) {
+            glyphs.add(s.getBounds2D());
+          }
+        };
+    GerberExporter.drawComponent(new Project(), g2d, new TextGerberComponent(side), false);
+    graphics.dispose();
+    return glyphs;
+  }
+
+  private static Rectangle2D union(List<Rectangle2D> rects) {
+    Rectangle2D union = (Rectangle2D) rects.get(0).clone();
+    for (Rectangle2D rect : rects) {
+      union.add(rect);
+    }
+    return union;
+  }
+
   private static GerberG2DWrapper draw(SimpleGerberComponent component) {
     BufferedImage img = new BufferedImage(100, 100, BufferedImage.TYPE_INT_ARGB);
     Graphics2D graphics = img.createGraphics();
@@ -126,4 +174,21 @@ public class GerberExporterTest {
       return side;
     }
   }
+
+  public static class TextGerberComponent extends SidedGerberComponent {
+
+    private static final long serialVersionUID = 1L;
+
+    public TextGerberComponent(PCBLayer side) {
+      super(side);
+    }
+
+    @Override
+    public void draw(Graphics2D g2d, ComponentState componentState, boolean outlineMode,
+        Project project, IDrawingObserver drawingObserver) {
+      g2d.setColor(Color.black);
+      g2d.setFont(new Font(Font.SANS_SERIF, Font.PLAIN, 20));
+      g2d.drawString("AB", 10, 50);
+    }
+  }
 }