GUI: improve chan osc wave centering

src/engine/workPool.cpp

@@ -0,0 +1,20 @@
+/**
+ * Furnace Tracker - multi-system chiptune tracker
+ * Copyright (C) 2021-2023 tildearrow and contributors
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+ #include "workPool.h"

src/engine/workPool.h

@@ -0,0 +1,66 @@
+/**
+ * Furnace Tracker - multi-system chiptune tracker
+ * Copyright (C) 2021-2023 tildearrow and contributors
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef _WORKPOOL_H
+#define _WORKPOOL_H
+
+#include <thread>
+#include <mutex>
+#include <functional>
+#include <condition_variable>
+
+struct DivWorkThread {
+  std::mutex lock;
+  std::thread* thread;
+  std::condition_variable notify;
+  bool busy, terminate;
+
+  void run();
+  DivWorkThread():
+    busy(false) {}
+};
+
+/**
+ * this class provides an implementation of a "thread pool" for executing tasks in parallel.
+ * it is highly recommended to use `new` when allocating a DivWorkPool.
+ */
+class DivWorkPool {
+  DivWorkThread* workThreads;
+  public:
+    /**
+     * push a new job to this work pool.
+     * if all work threads are busy, this will block until one is free.
+     */
+    bool push();
+    
+    /**
+     * check whether this work pool is busy.
+     */
+    bool busy();
+
+    /**
+     * wait for all work threads to finish.
+     */
+    bool wait();
+
+    DivWorkPool(unsigned int threads=0);
+    ~DivWorkPool();
+};
+
+#endif

src/gui/chanOsc.cpp

@@ -533,9 +533,9 @@ void FurnaceGUI::drawChanOsc() {
                     double dft[2];
                     dft[0]=0.0;
                     dft[1]=0.0;
-                    for (int j=0; j<waveLen; j++) {
-                      double one=((double)buf->data[(unsigned short)(needlePos-((int)waveLen)+j)&0xffff]/32768.0);
-                      double two=(double)j*(-2.0*M_PI)/waveLen;
+                    for (int j=needlePos-1-((displaySize+(int)waveLen)>>1), k=0; k<waveLen; j++, k++) {
+                      double one=((double)buf->data[j&0xffff]/32768.0);
+                      double two=(double)k*(-2.0*M_PI)/waveLen;
                       dft[0]+=one*cos(two);
                       dft[1]+=one*sin(two);
                     }
@@ -545,7 +545,7 @@ void FurnaceGUI::drawChanOsc() {
 
                     if (chanOscWaveCorr) {
                       needlePos-=phase*waveLen;
-                      needlePos-=(2*waveLen-fmod(displaySize,waveLen*2))*0.5;
+                       //needlePos-=(2*waveLen-fmod(displaySize,waveLen*2))*0.5;
                     }
                   }
                 }