Remove ModuleWidget::oldPos, store old module positions in RackWidget::Internal.

include/app/ModuleWidget.hpp

@@ -118,7 +118,6 @@ struct ModuleWidget : widget::OpaqueWidget {
 
 	PRIVATE math::Vec& dragOffset();
 	PRIVATE bool& dragEnabled();
-	PRIVATE math::Vec& oldPos();
 	PRIVATE engine::Module* releaseModule();
 };
 

src/app/ModuleWidget.cpp

@@ -36,12 +36,6 @@ struct ModuleWidget::Internal {
 	math::Vec dragRackPos;
 	bool dragEnabled = true;
 
-	/** The position in the RackWidget when dragging began.
-	Used for history::ModuleMove.
-	Set by RackWidget::updateModuleOldPositions() when *any* module begins dragging, since force-dragging can move other modules around.
-	*/
-	math::Vec oldPos;
-
 	widget::Widget* panel = NULL;
 };
 
@@ -1044,10 +1038,6 @@ bool& ModuleWidget::dragEnabled() {
 	return internal->dragEnabled;
 }
 
-math::Vec& ModuleWidget::oldPos() {
-	return internal->oldPos;
-}
-
 engine::Module* ModuleWidget::releaseModule() {
 	engine::Module* module = this->module;
 	this->module = NULL;

src/app/RackWidget.cpp

@@ -36,6 +36,7 @@ struct RackWidget::Internal {
 	math::Vec selectionStart;
 	math::Vec selectionEnd;
 	std::set<ModuleWidget*> selectedModules;
+	std::map<ModuleWidget*, math::Vec> moduleOldPositions;
 };
 
 
@@ -800,9 +801,9 @@ bool RackWidget::hasModules() {
 }
 
 void RackWidget::updateModuleOldPositions() {
-	// Set all modules' oldPos field from their current position.
+	internal->moduleOldPositions.clear();
 	for (ModuleWidget* mw : getModules()) {
-		mw->oldPos() = mw->box.pos;
+		internal->moduleOldPositions[mw] = mw->getPosition();
 	}
 }
 
@@ -812,7 +813,10 @@ history::ComplexAction* RackWidget::getModuleDragAction() {
 
 	for (ModuleWidget* mw : getModules()) {
 		// Create ModuleMove action if the module was moved.
-		math::Vec oldPos = mw->oldPos();
+		auto it = internal->moduleOldPositions.find(mw);
+		if (it == internal->moduleOldPositions.end())
+			continue;
+		math::Vec oldPos = it->second;
 		if (!oldPos.equals(mw->box.pos)) {
 			history::ModuleMove* mmh = new history::ModuleMove;
 			mmh->moduleId = mw->module->id;