ExpressionControlCommand.cc

// ExpressionControlCommand.h
#pragma once
#include <maya/MPxCommand.h>

class ExpressionControlCommand : public MPxCommand
{
public:
    MStatus doIt(const MArgList& argList) override;
    bool isUndoable() const override;

    static void* create();
    static MSyntax createSyntax();
};


// ExpressionControlCommand.cc
#include "ExpressionControlCommand.h"

#include <maya/MArgDatabase.h>
#include <maya/MSyntax.h>

// Include our custom widget
#include "ExpressionLineEdit.h"

#define kAttributeFlag "-a"
#define kAttributeFlagLong "-attribute"
#define kLabelFlag "-l"
#define kLabelFlagLong "-label"

MStatus ExpressionControlCommand::doIt(const MArgList& argList)
{
    MStatus status;
    MArgDatabase argDb(syntax(), argList);
    
    MString name;
    status = argDb.getCommandArgument(0, name);

    if(!status)
    {
        displayError("Control name is required!");
        return MS::kFailure;
	}

    MString nodeAttribute;
    if(argDb.isFlagSet(kAttributeFlag))
    {
        argDb.getFlagArgument(kAttributeFlag, 0, nodeAttribute);
    }
    else
    {
        displayError("A valid attribute needs to be specified!");
        return MS::kFailure;
    }

    MStringArray nodeAttributePair;
    nodeAttribute.split('.', nodeAttributePair);

    MSelectionList selList;
    selList.add(nodeAttributePair[0]);

    MObject node;
    selList.getDependNode(0, node);

    MFnDependencyNode nodeFn(node);
    MPlug attribute = nodeFn.findPlug(nodeAttributePair[1]);

    if(argDb.isEdit())
    {
        QWidget* widget = MQtUtil::findControl(name);

        if(!widget)
        {
            displayError("Unable to find an existing control with a given name!");
            return MS::kFailure;
        }

        // Update control to use the current attribute
        ExpressionLineEdit* control = static_cast<ExpressionLineEdit*>(widget);
        control->setAttribute(attribute);

        return MS::kSuccess;
    }

    QWidget* layout = MQtUtil::getCurrentParent();
    if(!layout)
    {
        displayError("Control must be created inside a valid layout!");
        return MS::kFailure;
    }

    MString label;
    if(argDb.isFlagSet(kLabelFlag))
    {
        argDb.getFlagArgument(kLabelFlag, 0, label);
    }
    else
    {
        label = attribute.partialName();
    }

    ExpressionLineEdit* control = new ExpressionLineEdit(attribute, MQtUtil::toQString(label));
    control->setObjectName(MQtUtil::toQString(name));

    MQtUtil::addWidgetToMayaLayout(control, layout);

    return MS::kSuccess;
}

bool ExpressionControlCommand::isUndoable() const
{
    return false;
}

void* ExpressionControlCommand::create()
{
    return new CreateExpressionControlCommand();
}

MSyntax ExpressionControlCommand::createSyntax()
{
    MSyntax syntax;

    syntax.enableEdit();
    syntax.addFlag(kAttributeFlag, kAttributeFlagLong, MSyntax::kString);
    syntax.addFlag(kLabelFlag, kLabelFlagLong, MSyntax::kString);
    syntax.addArg(MSyntax::kString);

    return syntax;
}