From 8d5052bf4efa0b90e68e21446ad42d53e8fe5097 Mon Sep 17 00:00:00 2001
From: Paul Licameli <paul.licameli@gmail.com>
Date: Tue, 2 Jun 2015 22:38:08 -0400
Subject: [PATCH] Avoid assertion violation while scrolling

---
 src/WaveClip.cpp | 50 +++++++++++++++++++++++++++++-------------------
 1 file changed, 30 insertions(+), 20 deletions(-)

diff --git a/src/WaveClip.cpp b/src/WaveClip.cpp
index a46f91766..c42e75ba5 100644
--- a/src/WaveClip.cpp
+++ b/src/WaveClip.cpp
@@ -499,7 +499,7 @@ namespace {
 inline
 void findCorrection(const sampleCount oldWhere[], int oldLen, int newLen,
          double t0, double rate, double samplesPerPixel,
-         double &oldWhere0, double &denom, int &oldX0, int &oldXLast, double &correction)
+         double &oldWhere0, double &denom, long &oldX0, long &oldXLast, double &correction)
 {
    // Mitigate the accumulation of location errors
    // in copies of copies of ... of caches.
@@ -511,25 +511,35 @@ void findCorrection(const sampleCount oldWhere[], int oldLen, int newLen,
    // Find the length in samples of the old cache.
    denom = oldWhereLast - oldWhere0;
 
-   // Skip unless denom rounds off to at least 1.
-   if (denom >= 0.5)
+   // What sample would go in where[0] with no correction?
+   const double guessWhere0 = t0 * rate;
+
+   // What integer position in the old cache array does that map to?
+   // (even if it is out of bounds)
+   oldX0 = floor(0.5 + oldLen * (guessWhere0 - oldWhere0) / denom);
+   // What sample count would the old cache have put there?
+   const double where0 = oldWhere0 + double(oldX0) * samplesPerPixel;
+   // What integer position in the old cache array does our last column
+   // map to?  (even if out of bounds)
+   oldXLast = floor(0.5 + oldLen * (
+      (where0 + double(newLen) * samplesPerPixel - oldWhere0)
+      / denom
+   ));
+
+   if ( // Skip if old and new are disjoint:
+      oldWhereLast <= guessWhere0 ||
+      guessWhere0 + newLen * samplesPerPixel <= oldWhere0 ||
+      // Skip unless denom rounds off to at least 1.
+      denom < 0.5)
+   {
+      correction = 0.0;
+   }
+   else
    {
-      // What sample would go in where[0] with no correction?
-      const double guessWhere0 = t0 * rate;
-      // What integer position in the old cache array does that map to?
-      // (even if it is out of bounds)
-      oldX0 = floor(0.5 + oldLen * (guessWhere0 - oldWhere0) / denom);
-      // What sample count would the old cache have put there?
-      const double where0 = oldWhere0 + double(oldX0) * samplesPerPixel;
       // What correction is needed to align the new cache with the old?
-      correction = where0 - guessWhere0;
-      wxASSERT(-samplesPerPixel <= correction && correction <= samplesPerPixel);
-      // What integer position in the old cache array does our last column
-      // map to?  (even if out of bounds)
-      oldXLast = floor(0.5 + oldLen * (
-         (where0 + double(newLen) * samplesPerPixel - oldWhere0)
-         / denom
-         ));
+      const double correction0 = where0 - guessWhere0;
+      correction = std::max(-samplesPerPixel, std::min(samplesPerPixel, correction0));
+      wxASSERT(correction == correction0);
    }
 }
 
@@ -599,7 +609,7 @@ bool WaveClip::GetWaveDisplay(WaveDisplay &display, double t0,
 
    double oldWhere0 = 0;
    double denom = 0;
-   int oldX0 = 0, oldXLast = 0;
+   long oldX0 = 0, oldXLast = 0;
    double correction = 0.0;
    if (match &&
        oldCache->len > 0) {
@@ -918,7 +928,7 @@ bool WaveClip::GetSpectrogram(WaveTrackCache &waveTrackCache,
    // reuse and finding corrections
    double oldWhere0 = 0;
    double denom = 0;
-   int oldX0 = 0, oldXLast = 0;
+   long oldX0 = 0, oldXLast = 0;
    double correction = 0.0;
 
    if (match &&