Fixed WinDirStat's completely broken visualisation

The bug is caused by the fact that an unsigned long long minus an
unsigned long long is ALWAYS positive. The quicksort function algorithm used
`signum` to compare unsigned long longs. With signum
always returning either 1 or 0 (because always positive), the sorting was
pretty much useless. With an arbitrary sorting order in multiple locations of
the program, nothing was grouped correctly and the wrong file extensions got a
colour assigned.

The bug was introduced in revision 151.

5 files changed, 14 insertions, 11 deletions

diff --git a/windirstat/Controls/typeview.cpp b/windirstat/Controls/typeview.cpp
index 756bd7e..9b09372 100644
--- a/windirstat/Controls/typeview.cpp
+++ b/windirstat/Controls/typeview.cpp
@@ -182,13 +182,13 @@ int CExtensionListControl::CListItem::Compare(const CSortingListItem *baseOther,
     case COL_COLOR:
     case COL_BYTES:
         {
-            r = signum(m_record.bytes - other->m_record.bytes);
+            r = usignum(m_record.bytes, other->m_record.bytes);
         }
         break;
 
     case COL_FILES:
         {
-            r = signum(m_record.files - other->m_record.files);
+            r = usignum(m_record.files, other->m_record.files);
         }
         break;
 
diff --git a/windirstat/Dialogs/SelectDrivesDlg.cpp b/windirstat/Dialogs/SelectDrivesDlg.cpp
index 7232211..7b23e21 100644
--- a/windirstat/Dialogs/SelectDrivesDlg.cpp
+++ b/windirstat/Dialogs/SelectDrivesDlg.cpp
@@ -166,12 +166,12 @@ int CDriveItem::Compare(const CSortingListItem *baseOther, int subitem) const
         break;
     case COL_TOTAL:
         {
-            r = signum(m_totalBytes - other->m_totalBytes);
+            r = usignum(m_totalBytes, other->m_totalBytes);
         }
         break;
     case COL_FREE:
         {
-            r = signum(m_freeBytes - other->m_freeBytes);
+            r = usignum(m_freeBytes, other->m_freeBytes);
         }
         break;
     case COL_GRAPH:
diff --git a/windirstat/dirstatdoc.cpp b/windirstat/dirstatdoc.cpp
index 01277ec..61e66c2 100644
--- a/windirstat/dirstatdoc.cpp
+++ b/windirstat/dirstatdoc.cpp
@@ -808,7 +808,7 @@ int __cdecl CDirstatDoc::_compareExtensions(const void *item1, const void *item2
     SExtensionRecord r2;
     VERIFY(_pqsortExtensionData->Lookup(*ext1, r1));
     VERIFY(_pqsortExtensionData->Lookup(*ext2, r2));
-    return signum(r2.bytes - r1.bytes);
+    return usignum(r2.bytes, r1.bytes);
 }
 
 void CDirstatDoc::SetWorkingItemAncestor(CItem *item)
diff --git a/windirstat/item.cpp b/windirstat/item.cpp
index 0219fe7..e4f188c 100644
--- a/windirstat/item.cpp
+++ b/windirstat/item.cpp
@@ -277,7 +277,7 @@ int CItem::CompareSibling(const CTreeListItem *tlib, int subitem) const
     case COL_SUBTREEPERCENTAGE:
         if(MustShowReadJobs())
         {
-            r = signum(m_readJobs - other->m_readJobs);
+            r = usignum(m_readJobs, other->m_readJobs);
         }
         else
         {
@@ -293,25 +293,25 @@ int CItem::CompareSibling(const CTreeListItem *tlib, int subitem) const
 
     case COL_SUBTREETOTAL:
         {
-            r = signum(GetSize() - other->GetSize());
+            r = usignum(GetSize(), other->GetSize());
         }
         break;
 
     case COL_ITEMS:
         {
-            r = signum(GetItemsCount() - other->GetItemsCount());
+            r = usignum(GetItemsCount(), other->GetItemsCount());
         }
         break;
 
     case COL_FILES:
         {
-            r = signum(GetFilesCount() - other->GetFilesCount());
+            r = usignum(GetFilesCount(), other->GetFilesCount());
         }
         break;
 
     case COL_SUBDIRS:
         {
-            r = signum(GetSubdirsCount() - other->GetSubdirsCount());
+            r = usignum(GetSubdirsCount(), other->GetSubdirsCount());
         }
         break;
 
@@ -1650,7 +1650,7 @@ int __cdecl CItem::_compareBySize(const void *p1, const void *p2)
 
     // TODO: Use 2nd sort column (as set in our TreeListView?)
 
-    return signum(size2 - size1); // biggest first
+    return usignum(size2, size1); // biggest first
 }
 
 ULONGLONG CItem::GetProgressRangeMyComputer() const
diff --git a/windirstat/stdafx.h b/windirstat/stdafx.h
index 1514704..8c34010 100644
--- a/windirstat/stdafx.h
+++ b/windirstat/stdafx.h
@@ -78,6 +78,9 @@
 
 template<class T> int signum(T x) { return (x) < 0 ? -1 : (x) == 0 ? 0 : 1; }
 
+/// signum function for unsigned numbers.
+template<class T> int usignum(T x, T y) { return (x) < (y) ? -1 : (x) == (y) ? 0 : 1; }
+
 #define WEAK_ASSERT /##/ ASSERT
 
 #endif // __WDS_STDAFX_H__