1 files changed, 122 insertions, 0 deletions
diff --git a/src/demos/xtrans/OffscreenComponentWrapper.java b/src/demos/xtrans/OffscreenComponentWrapper.java
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+++ b/src/demos/xtrans/OffscreenComponentWrapper.java
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+package demos.xtrans;
+
+import java.awt.*;
+import javax.swing.*;
+
+// Internal JOGL API references
+import com.sun.opengl.impl.Debug;
+// FIXME: debugging only
+import com.sun.opengl.impl.Java2D;
+
+/** Provides an interposition point where we can install a new
+    Graphics object in the rendering pipeline. Because lightweight
+    components always delegate up to their parents to fetch Graphics
+    objects, we can use this point to swap in the off-screen
+    VolatileImage we're using for rendering. Applications should not
+    need to construct instances of this class directly, though they
+    may encounter them when traversing the component hierarchy created
+    by the OffscreenDesktopPane, since they are automatically inserted
+    during add operations. */
+
+public class OffscreenComponentWrapper extends JComponent {
+  private static final boolean DEBUG = Debug.debug("OffscreenComponentWrapper");
+
+  /** Instantiates an OffscreenComponentWrapper. This should not be
+      called directly by applications. */
+  public OffscreenComponentWrapper(Component arg) {
+    if (arg == null) {
+      throw new RuntimeException("Null argument");
+    }
+    add(arg);
+    setOpaque(false);
+  }
+
+  protected void addImpl(Component c, Object constraints, int index) {
+    if (getComponentCount() != 0) {
+      throw new RuntimeException("May only add one child");
+    }
+    super.addImpl(c, constraints, index);
+  }
+
+  /** Returns the sole child component of this one. */
+  public Component getChild() {
+    if (getComponentCount() == 0) {
+      throw new RuntimeException("No child found");
+    }
+    return getComponent(0);
+  }
+
+  public void remove(int i) {
+    super.remove(i);
+    throw new RuntimeException("Should not call this");
+  }
+
+  public void remove(Component c) {
+    super.remove(c);
+    throw new RuntimeException("Should not call this");
+  }
+
+  /** Overrides the superclass's getGraphics() in order to provide a
+      correctly-translated Graphics object on the
+      OffscreenDesktopPane's back buffer. */
+  public Graphics getGraphics() {
+    Component parent = getParent();
+    if ((parent != null) && (parent instanceof OffscreenDesktopPane)) {
+      OffscreenDesktopPane desktop = (OffscreenDesktopPane) parent;
+      OffscreenDesktopManager manager = (OffscreenDesktopManager) desktop.getDesktopManager();
+      // Find out where the component we're rendering lives on the back buffer
+      Graphics g = manager.getOffscreenGraphics();
+      Rectangle bounds = manager.getBoundsOnBackBuffer(getChild());
+      if (bounds == null) {
+        if (DEBUG) {
+          System.err.println("No bounds for child");
+        }
+
+        // Not yet laid out on back buffer; however, avoid painting to
+        // screen
+        return g;
+      }
+      if (DEBUG) {
+        System.err.println("Graphics.translate(" + bounds.x + "," + bounds.y + ")");
+        System.err.println("  Surface identifier = " + Java2D.getOGLSurfaceIdentifier(g));
+      }
+
+      g.translate(bounds.x, bounds.y);
+      // Also take into account the translation of the child
+      Component c = getChild();
+      g.translate(-c.getX(), -c.getY());
+      // Make sure any changes the user made to the double-buffering
+      // of child components don't mess up the rendering results
+      OffscreenDesktopManager.switchDoubleBuffering(this, false);
+      // A child component will be performing drawing and therefore
+      // get the OpenGL copy of the back buffer out of sync; will need
+      // to repair it
+      // NOTE: in theory we should only need to set the copy back
+      // state on the OffscreenDesktopManager. However it seems that
+      // there are certain operations (like scrolling in a
+      // JScrollPane) that have unanticipated consequences, such as
+      // drawing into the Swing back buffer (which is heavily
+      // undesirable, because it can cause on-screen visual artifacts
+      // in our rendering paradigm) as well as potentially
+      // inadvertently copying regions of the back buffer from one
+      // place to another. Since we don't know the side effects of
+      // such operations we currently need to treat the entire back
+      // buffer as being dirty.
+      manager.setNeedsRedraw();
+      // NOTE: this is a bit of a hack but we need to indicate to the
+      // parent desktop that it is dirty as well since one of its
+      // children (being painted by alternate means) needs to be
+      // redrawn
+      desktop.repaint();
+      return g;
+    } else {
+      return super.getGraphics();
+    }
+  }
+
+  public void paintComponent(Graphics g) {
+  }
+
+  protected void paintChildren(Graphics g) {
+  }
+}