draw manager: lazily fetch screenshot image

Also no longer pass images to every frame listener. With GPU rendering
it is expensive to get Images each frame.

runelite-client/src/main/java/net/runelite/client/callback/Hooks.java

@@ -283,6 +283,7 @@ public class Hooks implements Callbacks
 		}
 
 		Image image = mainBufferProvider.getImage();
+		final Image finalImage;
 		final Graphics2D graphics2d = (Graphics2D) image.getGraphics();
 
 		try
@@ -334,13 +335,17 @@ public class Hooks implements Callbacks
 					: RenderingHints.VALUE_INTERPOLATION_BILINEAR);
 			stretchedGraphics.drawImage(image, 0, 0, stretchedDimensions.width, stretchedDimensions.height, null);
 
-			image = stretchedImage;
+			finalImage = image = stretchedImage;
+		}
+		else
+		{
+			finalImage = image;
 		}
 
 		// Draw the image onto the game canvas
 		graphics.drawImage(image, 0, 0, client.getCanvas());
 
-		drawManager.processDrawComplete(image);
+		drawManager.processDrawComplete(() -> finalImage);
 	}
 
 	@Override

runelite-client/src/main/java/net/runelite/client/plugins/fps/FpsDrawListener.java

@@ -24,8 +24,6 @@
  */
 package net.runelite.client.plugins.fps;
 
-import java.awt.Image;
-import java.util.function.Consumer;
 import javax.inject.Inject;
 import net.runelite.api.events.FocusChanged;
 
@@ -42,7 +40,7 @@ import net.runelite.api.events.FocusChanged;
  * Enforcing FPS in the draw code does not impact the client engine's ability to run including its audio,
  * even when forced to 1 FPS with this plugin.
  */
-public class FpsDrawListener implements Consumer<Image>
+public class FpsDrawListener implements Runnable
 {
 	private static final int SAMPLE_SIZE = 4;
 
@@ -90,7 +88,7 @@ public class FpsDrawListener implements Consumer<Image>
 	}
 
 	@Override
-	public void accept(Image image)
+	public void run()
 	{
 
 		if (!isEnforced())

runelite-client/src/main/java/net/runelite/client/ui/DrawManager.java

@@ -30,6 +30,7 @@ import java.util.Queue;
 import java.util.concurrent.ConcurrentLinkedQueue;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.function.Consumer;
+import java.util.function.Supplier;
 import javax.inject.Singleton;
 import lombok.extern.slf4j.Slf4j;
 
@@ -37,10 +38,10 @@ import lombok.extern.slf4j.Slf4j;
 @Slf4j
 public class DrawManager
 {
-	private final List<Consumer<Image>> everyFrame = new CopyOnWriteArrayList<>();
+	private final List<Runnable> everyFrame = new CopyOnWriteArrayList<>();
 	private final Queue<Consumer<Image>> nextFrame = new ConcurrentLinkedQueue<>();
 
-	public void registerEveryFrameListener(Consumer<Image> everyFrameListener)
+	public void registerEveryFrameListener(Runnable everyFrameListener)
 	{
 		if (!everyFrame.contains(everyFrameListener))
 		{
@@ -48,7 +49,7 @@ public class DrawManager
 		}
 	}
 
-	public void unregisterEveryFrameListener(Consumer<Image> everyFrameListener)
+	public void unregisterEveryFrameListener(Runnable everyFrameListener)
 	{
 		everyFrame.remove(everyFrameListener);
 	}
@@ -58,13 +59,13 @@ public class DrawManager
 		nextFrame.add(nextFrameListener);
 	}
 
-	public void processDrawComplete(Image image)
+	public void processDrawComplete(Supplier<Image> imageSupplier)
 	{
-		for (Consumer<Image> everyFrameListener : everyFrame)
+		for (Runnable everyFrameListener : everyFrame)
 		{
 			try
 			{
-				everyFrameListener.accept(image);
+				everyFrameListener.run();
 			}
 			catch (Exception e)
 			{
@@ -73,8 +74,27 @@ public class DrawManager
 		}
 
 		Consumer<Image> nextFrameListener = nextFrame.poll();
+		Image image = null;
 		while (nextFrameListener != null)
 		{
+			if (image == null)
+			{
+				try
+				{
+					image = imageSupplier.get();
+				}
+				catch (Exception ex)
+				{
+					log.warn("error getting screenshot", ex);
+				}
+			}
+
+			if (image == null)
+			{
+				nextFrame.clear();
+				break;
+			}
+
 			try
 			{
 				nextFrameListener.accept(image);