private void updateSelectionToViewportBottom() {
		int bottomRow = getViewportPositionAsRow() + getNumRowsInViewport();
		
		Pair filePos = model.getFilePositionForRow(bottomRow);
		if (filePos == null) {
			return;
		}
		long filePosForBottomRow = filePos.getEnd();
		model.selectedByteEnd = filePosForBottomRow;
		table.restoreSelection();
	}
Sets the last row in the viewport to be the end of the current selection range.  The 
start of the selection range remains untouched.
Ghidra/Framework/Project/src/main/java/ghidra/framework/main/logviewer/ui/ViewportUtility.java