Codechange: Rely on Scrollbar::SetPosition to clamp.

Manually clamping scrollbar bounds before calling `SetPosition()` is doubling up work that the function already does.

src/script/script_gui.cpp

@@ -860,11 +860,10 @@ struct ScriptDebugWindow : public Window {
 		/* Detect when the user scrolls the window. Enable autoscroll when the
 		 * bottom-most line becomes visible. */
 		if (this->last_vscroll_pos != this->vscroll->GetPosition()) {
-			this->autoscroll = this->vscroll->GetPosition() >= log.size() - this->vscroll->GetCapacity();
+			this->autoscroll = this->vscroll->GetPosition() + this->vscroll->GetCapacity() >= (int)log.size();
 		}
 		if (this->autoscroll) {
-			int scroll_pos = std::max<int>(0, (int)log.size() - this->vscroll->GetCapacity());
-			if (this->vscroll->SetPosition(scroll_pos)) {
+			if (this->vscroll->SetPosition((int)log.size())) {
 				/* We need a repaint */
 				this->SetWidgetDirty(WID_SCRD_SCROLLBAR);
 				this->SetWidgetDirty(WID_SCRD_LOG_PANEL);

src/window.cpp

@@ -2379,13 +2379,10 @@ static void HandleScrollbarScrolling(Window *w)
 		return;
 	}
 
-	/* Find the item we want to move to and make sure it's inside bounds. */
-	int pos = std::min(RoundDivSU(std::max(0, i + _scrollbar_start_pos) * sb->GetCount(), _scrollbar_size), std::max(0, sb->GetCount() - sb->GetCapacity()));
-	if (rtl) pos = std::max(0, sb->GetCount() - sb->GetCapacity() - pos);
-	if (pos != sb->GetPosition()) {
-		sb->SetPosition(pos);
-		w->SetDirty();
-	}
+	/* Find the item we want to move to. SetPosition will make sure it's inside bounds. */
+	int pos = RoundDivSU((i + _scrollbar_start_pos) * sb->GetCount(), _scrollbar_size);
+	if (rtl) pos = sb->GetCount() - sb->GetCapacity() - pos;
+	if (sb->SetPosition(pos)) w->SetDirty();
 }
 
 /**