Fix ModuleWidget::getParam(), getInput(), and getOutput() returning incorrect object.

include/app/ModuleWidget.hpp

@@ -19,6 +19,8 @@ struct ModuleWidget : widget::OpaqueWidget {
 	engine::Module *module = NULL;
 
 	widget::Widget *panel = NULL;
+	/** Note that the indexes of these vectors might not correspond with the indexes of `Module::params` etc.
+	*/
 	std::vector<ParamWidget*> params;
 	std::vector<PortWidget*> outputs;
 	std::vector<PortWidget*> inputs;

include/history.hpp

@@ -20,6 +20,11 @@ namespace app {
 namespace history {
 
 
+/** An undo action with an inverse redo action.
+
+Pointers to Modules, Params, etc. are not allowed in Actions because the object they refer to may be deleted and restored.
+Instead, use moduleIds, etc.
+*/
 struct Action {
 	/** Name of the action, lowercase. Used in the phrase "Undo ..." */
 	std::string name;
@@ -51,7 +56,7 @@ struct ComplexAction : Action {
 };
 
 
-/** An action operating on a module
+/** An action operating on a module.
 Subclass this to create your own custom actions for your module.
 */
 struct ModuleAction : Action {

src/app/ModuleWidget.cpp

@@ -415,20 +415,26 @@ void ModuleWidget::addInput(PortWidget *input) {
 }
 
 ParamWidget *ModuleWidget::getParam(int paramId) {
-	if (0 <= paramId && paramId < (int) params.size())
-		return params[paramId];
+	for (ParamWidget *param : params) {
+		if (param->paramQuantity && param->paramQuantity->paramId == paramId)
+			return param;
+	}
 	return NULL;
 }
 
 PortWidget *ModuleWidget::getOutput(int outputId) {
-	if (0 <= outputId && outputId < (int) outputs.size())
-		return outputs[outputId];
+	for (PortWidget *port : outputs) {
+		if (port->portId == outputId)
+			return port;
+	}
 	return NULL;
 }
 
 PortWidget *ModuleWidget::getInput(int inputId) {
-	if (0 <= inputId && inputId < (int) inputs.size())
-		return inputs[inputId];
+	for (PortWidget *port : inputs) {
+		if (port->portId == inputId)
+			return port;
+	}
 	return NULL;
 }