GUI: add advanced VGM export menu

does NOT work yet!

src/engine/engine.cpp

@@ -625,6 +625,29 @@ DivInstrumentType DivEngine::getPreferInsType(int chan) {
   return DIV_INS_FM;
 }
 
+bool DivEngine::isVGMExportable(DivSystem which) {
+  switch (which) {
+    case DIV_SYSTEM_GENESIS:
+    case DIV_SYSTEM_GENESIS_EXT:
+    case DIV_SYSTEM_SMS:
+    case DIV_SYSTEM_GB:
+    case DIV_SYSTEM_PCE:
+    case DIV_SYSTEM_NES:
+    case DIV_SYSTEM_ARCADE:
+    case DIV_SYSTEM_YM2151:
+    case DIV_SYSTEM_YM2612:
+    case DIV_SYSTEM_YM2610:
+    case DIV_SYSTEM_YM2610_EXT:
+    case DIV_SYSTEM_AY8910:
+    case DIV_SYSTEM_AY8930:
+    case DIV_SYSTEM_SAA1099:
+      return true;
+    default:
+      return false;
+  }
+  return false;
+}
+
 const char* DivEngine::getEffectDesc(unsigned char effect, int chan) {
   switch (effect) {
     case 0x00:

src/engine/engine.h

@@ -234,6 +234,9 @@ class DivEngine {
     // notify wavetable change
     void notifyWaveChange(int wave);
 
+    // returns whether a system is VGM compatible
+    bool isVGMExportable(DivSystem which);
+
     // save config
     bool saveConf();
 

src/gui/gui.cpp

@@ -4038,9 +4038,34 @@ bool FurnaceGUI::loop() {
         }
         ImGui::EndMenu();
       }
-      if (ImGui::MenuItem("export VGM...")) {
+      if (ImGui::BeginMenu("export VGM...")) {
+        ImGui::Text("settings:");
+        ImGui::Checkbox("loop",&vgmExportLoop);
+        ImGui::Text("systems to export:");;
+        bool hasOneAtLeast=false;
+        for (int i=0; i<e->song.systemLen; i++) {
+          ImGui::BeginDisabled(!e->isVGMExportable(e->song.system[i]));
+          ImGui::Checkbox(fmt::sprintf("%d. %s##_SYSV%d",i+1,e->getSystemName(e->song.system[i]),i).c_str(),&willExport[i]);
+          ImGui::EndDisabled();
+          if (!e->isVGMExportable(e->song.system[i])) {
+            if (ImGui::IsItemHovered(ImGuiHoveredFlags_AllowWhenDisabled)) {
+              ImGui::SetTooltip("this system is not supported by the VGM format!");
+            }
+          } else {
+            if (willExport[i]) hasOneAtLeast=true;
+          }
+        }
+        ImGui::Text("select the systems you wish to export,");
+        ImGui::Text("but only up to 2 of each type.");
+        if (hasOneAtLeast) {
+          if (ImGui::MenuItem("click to export")) {
             openFileDialog(GUI_FILE_EXPORT_VGM);
           }
+        } else {
+          ImGui::Text("nothing to export");
+        }
+        ImGui::EndMenu();
+      }
       ImGui::Separator();
       if (ImGui::BeginMenu("add system...")) {
         sysAddOption(DIV_SYSTEM_GENESIS);
@@ -4742,6 +4767,7 @@ FurnaceGUI::FurnaceGUI():
   modified(false),
   displayError(false),
   displayExporting(false),
+  vgmExportLoop(true),
   curFileDialog(GUI_FILE_OPEN),
   warnAction(GUI_WARN_OPEN),
   scrW(1280),
@@ -4869,4 +4895,6 @@ FurnaceGUI::FurnaceGUI():
   valueKeys[SDLK_d]=13;
   valueKeys[SDLK_e]=14;
   valueKeys[SDLK_f]=15;
+
+  memset(willExport,1,32*sizeof(bool));
 }

src/gui/gui.h

@@ -162,7 +162,8 @@ class FurnaceGUI {
 
   String workingDir, fileName, clipboard, warnString, errorString, lastError, curFileName;
 
-  bool quit, warnQuit, willCommit, edit, modified, displayError, displayExporting;
+  bool quit, warnQuit, willCommit, edit, modified, displayError, displayExporting, vgmExportLoop;
+  bool willExport[32];
 
   FurnaceGUIFileDialogs curFileDialog;
   FurnaceGUIWarnings warnAction;