Fixed ClassCastException bug in PostWindow.

Fixed page flipping in RichTextPane3, after last bug fix.

PostWindow.java

@@ -29,6 +29,7 @@ import java.awt.Image;
 import java.awt.Component;
 import java.awt.event.ActionListener;
 import java.awt.event.ActionEvent;
+import java.awt.MediaTracker;
 import java.util.List;
 import java.util.ArrayList;
 import java.net.URL;
@@ -428,7 +429,49 @@ implements ActionListener {
     setAuthorId(String n) { authorId.setText(n); }
 
 	public void
-	setAuthorAvatar(Image n) { profile.setImage(n); }
+	setAuthorAvatar(Image n)
+	{
+		try {
+			MediaTracker mt = new MediaTracker(this);
+			mt.addImage(n, 0);
+			mt.waitForID(0);
+		}
+		catch (InterruptedException eIt) {
+			assert false;
+		}
+		/*
+		* Blocks until the image loads. We have to do this because
+		* there is an unfixed JDK bug in Image#getScaledInstance
+		* (which RoundButton uses) where when you pass it an AWT
+		* image, it incorrectly sets the ColorModel's transfer type,
+		* causing a ClassCastException, and returns a valid image
+		* with blank data. It seems using loaded images does not
+		* replicate the issue, which would explain why the bug
+		* hasn't been found and fixed..
+		*
+		* For future readers wondering. JDK 11, up to JDK 15.
+		* java.awt.image.ColorModel#getAlpha(:845), who was called
+		* sun.awt.image.ImageRepresentation#convertToRGB, who was
+		* called by AreaAveragingScaleFilter trying to #setPixels.
+		* Cause RoundButton was using Image.SCALE_SMOOTH.
+		*
+		* I guess it kind of makes sense, why would I try to get a
+		* scaled instance of an image that hadn't finished loading.
+		* An intelligent class would render the awt.Image as-is until
+		* it has completely loaded, then call #getScaledInstance
+		* instead. I won't have RoundButton do that for now, as
+		* my other classes like RichTextPane3 might have this too.
+		*
+		* If you asked me how I'd generalise the solution. My
+		* expectation had been that #getScaledInstance waits for
+		* the image too, returning a null image until it's done.
+		* So I'd put a #getScaledInstance in ImageApi, which does
+		* this, using MediaTracker. That assumes what I'm doing
+		* right now definitely works.
+		*/
+
+		profile.setImage(n);
+	}
 
     public void
     setDate(String n) { date.setText(n); }

RichTextPane3.java

@@ -39,7 +39,7 @@ implements
 	layoutEnd, selStart, selEnd;
 
 	private int
-	startingLine, endingLine;
+	startingLine, lastLine;
 
 //	---%-@-%---
 
@@ -77,7 +77,7 @@ implements
 		startingLine = 1;
 		layout(html, fm, cursor);
 		layout.put(layoutEnd, cursor.clone());
-		endingLine = cursor.line;
+		lastLine = cursor.line;
 		repaint();
 
 		int iy = fm.getAscent();
@@ -108,7 +108,7 @@ implements
 	nextPage()
 	{
 		int advance = getHeightInLines();
-		if (endingLine - startingLine < advance) return;
+		if (lastLine - startingLine < advance) return;
 		else startingLine += advance;
 		repaint();
 	}
@@ -557,7 +557,7 @@ implements
 		FontMetrics fm = getFontMetrics(getFont());
         int initial = fm.getAscent();
         int advance = fm.getAscent() + fm.getDescent();
-		return isnap2(getHeight(), initial, advance);
+		return isnap2(getHeight(), initial, advance) - 1;
 	}
 
     public void

TwoToggleButton.java

@@ -298,8 +298,6 @@ implements KeyListener, MouseListener, FocusListener {
 
 		int ow = image.getWidth(this);
 		int oh = image.getHeight(this);
-		if (ow == -1) return;
-
 		int nx = 6;
 		int ny = 6;
 		int nw = button.getWidth(this) - 12;
@@ -312,6 +310,8 @@ implements KeyListener, MouseListener, FocusListener {
 		{
 			int sw = ow > oh ? -1 : nw;
 			int sh = oh > ow ? -1 : nh;
+			// We do not defend against unloaded images. There is
+			// a bug on those anyways, see comment in PostWindow.
 			scaled = image.getScaledInstance(
 				sw, sh,
 				Image.SCALE_SMOOTH