From ab1a045d10e9e3e24f731086d6354336253f8b81 Mon Sep 17 00:00:00 2001
From: Stefan Schimanski <sts@lyx.org>
Date: Sat, 26 Jan 2008 00:47:22 +0000
Subject: [PATCH] * fix random jumps when scrolling very fast using a touchpad
 or mouse wheel.

The problem was this: The value in BufferView::scrollDocView(int value) is
relative to the d->scrollbarParameters_.min/max interval and _not_ absolute.


git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@22675 a592a061-630c-0410-9148-cb99ea01b6c8
---
 src/BufferView.cpp | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/BufferView.cpp b/src/BufferView.cpp
index 2a543ff5a7..e563a4f81d 100644
--- a/src/BufferView.cpp
+++ b/src/BufferView.cpp
@@ -508,7 +508,12 @@ void BufferView::scrollDocView(int value)
 		return;
 	}
 
-	int par_pos = 0;
+	// cut off at the top
+	if (value < d->scrollbarParameters_.min)
+		value = d->scrollbarParameters_.min;
+
+	// find paragraph at target positin
+	int par_pos = d->scrollbarParameters_.min;
 	for (size_t i = 0; i != d->par_height_.size(); ++i) {
 		par_pos += d->par_height_[i];
 		if (par_pos >= value) {
@@ -521,7 +526,15 @@ void BufferView::scrollDocView(int value)
 		<< "\tanchor_ref_ = " << d->anchor_pit_
 		<< "\tpar_pos = " << par_pos);
 
+	// cut off at the end of the buffer
+	if (value > par_pos) {
+		value = d->scrollbarParameters_.max;
+		d->anchor_pit_ = d->par_height_.size() - 1;
+	}
+
+	// set pixel offset of screen to anchor pit
 	d->anchor_ypos_ = par_pos - value;
+
 	updateMetrics();
 	buffer_.changed();
 }