Codechange: Don't update window contents if scrollbar position has not moved.

1 files changed, 8 insertions, 4 deletions

diff --git a/src/widget_type.h b/src/widget_type.h
index 200711356..c50a263d6 100644
--- a/src/widget_type.h
+++ b/src/widget_type.h
@@ -737,12 +737,15 @@ public:
 	/**
 	 * Sets the position of the first visible element
 	 * @param position the position of the element
+	 * @return true iff the position has changed
 	 */
-	void SetPosition(int position)
+	bool SetPosition(int position)
 	{
 		assert(position >= 0);
 		assert(this->count <= this->cap ? (position == 0) : (position + this->cap <= this->count));
+		uint16 old_pos = this->pos;
 		this->pos = position;
+		return this->pos != old_pos;
 	}
 
 	/**
@@ -750,16 +753,17 @@ public:
 	 * If the position would be too low or high it will be clamped appropriately
 	 * @param difference the amount of change requested
 	 * @param unit The stepping unit of \a difference
+	 * @return true iff the position has changed
 	 */
-	void UpdatePosition(int difference, ScrollbarStepping unit = SS_SMALL)
+	bool UpdatePosition(int difference, ScrollbarStepping unit = SS_SMALL)
 	{
-		if (difference == 0) return;
+		if (difference == 0) return false;
 		switch (unit) {
 			case SS_SMALL: difference *= this->stepsize; break;
 			case SS_BIG:   difference *= this->cap; break;
 			default: break;
 		}
-		this->SetPosition(Clamp(this->pos + difference, 0, std::max(this->count - this->cap, 0)));
+		return this->SetPosition(Clamp(this->pos + difference, 0, std::max(this->count - this->cap, 0)));
 	}
 
 	/**