Render optimization (#1087)

* Caching and culling improvements

* doc

* Update canvas-rendering-cache-and-culling.md

* caching for wires

* cache invalidation improvements

* caching improvements

* twisted wire performance update

* Improved grid rendering on screen and when exporting; PDF export of the grid is now vector-based and does not get blurry on zooming in

* area append improvement

* bug fix for subtracting trace cuts

* Twisted wire stroke render improvement

* various performance improvements

* lazy area merging

* regression update

* Update update.xml

* code cleanup

* Twisted wire border thickness fix

diylc/diylc-swing/src/main/java/org/diylc/swing/plugins/canvas/CanvasPanel.java

@@ -306,7 +306,11 @@ public class CanvasPanel extends JComponent implements Autoscroll {
     
     Rectangle visibleRect = getVisibleRect();
 
-    if (bufferImage == null) {
+    // the buffer is redrawn in full on every paint, so only a change in size, which includes the
+    // HiDPI scale, calls for a new one; scrolling does not
+    if (bufferImage == null
+        || bufferImage.getWidth() != (int) Math.round(visibleRect.width * scaleFactor)
+        || bufferImage.getHeight() != (int) Math.round(visibleRect.height * scaleFactor)) {
       createBufferImage(visibleRect, scaleFactor);
     }
     Graphics2D bufferG2d = (Graphics2D) bufferImage.getGraphics();

diylc/diylc-swing/src/main/java/org/diylc/swing/plugins/canvas/CanvasPlugin.java

@@ -118,7 +118,6 @@ public class CanvasPlugin implements IPlugIn{
 
         @Override
         public void adjustmentValueChanged(AdjustmentEvent e) {
-          getCanvasPanel().invalidateCache();
           getCanvasPanel().revalidate();
         }
       });
@@ -127,7 +126,6 @@ public class CanvasPlugin implements IPlugIn{
 
         @Override
         public void adjustmentValueChanged(AdjustmentEvent e) {
-          getCanvasPanel().invalidateCache();
           getCanvasPanel().revalidate();
         }
       });