add option to remove unused patterns

src/engine/song.cpp

@@ -278,6 +278,24 @@ void DivSubSong::clearData() {
   ordersLen=1;
 }
 
+void DivSubSong::removeUnusedPatterns() {
+  for (int i=0; i<DIV_MAX_CHANS; i++) {
+    bool used[DIV_MAX_PATTERNS];
+    memset(used,0,DIV_MAX_PATTERNS*sizeof(bool));
+
+    for (int j=0; j<ordersLen; j++) {
+      used[orders.ord[i][j]]=true;
+    }
+
+    for (int j=0; j<DIV_MAX_PATTERNS; j++) {
+      if (!used[j] && pat[i].data[j]!=NULL) {
+        delete pat[i].data[j];
+        pat[i].data[j]=NULL;
+      }
+    }
+  }
+}
+
 void DivSubSong::optimizePatterns() {
   for (int i=0; i<DIV_MAX_CHANS; i++) {
     logD("optimizing channel %d...",i);

src/engine/song.h

@@ -196,6 +196,7 @@ struct DivSubSong {
   void findLength(int loopOrder, int loopRow, double fadeoutLen, int& rowsForFadeout, bool& hasFFxx, std::vector<int>& orders, std::vector<DivGroovePattern>& grooves, int& length, int chans, int jumpTreatment, int ignoreJumpAtEnd, int firstPat=0);
 
   void clearData();
+  void removeUnusedPatterns();
   void optimizePatterns();
   void rearrangePatterns();
   void sortOrders();

src/gui/gui.cpp

@@ -6553,6 +6553,14 @@ bool FurnaceGUI::loop() {
               MARK_MODIFIED;
               ImGui::CloseCurrentPopup();
             }
+            if (ImGui::Button(_("Remove unused patterns"))) {
+              stop();
+              e->lockEngine([this]() {
+                e->curSubSong->removeUnusedPatterns();
+              });
+              MARK_MODIFIED;
+              ImGui::CloseCurrentPopup();
+            }
             if (ImGui::Button(_("Remove unused instruments"))) {
               stop();
               e->delUnusedIns();