Create a Raw C++ DLL for Xojo

This example shows how to create a simple function that adds two numbers together by creating a simple DLL in C++ with Visual Studio 2019 that can be used in Xojo 2019 r1.1. The secret is that the functions will need to have "C"-like names to prevent name mangling. This example is for 64-bit applications.

Raw Plugin Screen Grab

Here are the steps to create the plugin in Visual Studio 2019 and read the DLL in Xojo.

Start Visual Studio 2019
Create a new project
Select Dynamic-Link Library with exports (DLL)
Create project name RawPluginCPlusPlus code

Add code to RawPluginCPlusPlusCode.cpp

// RawPluginCPlusPlusCode.cpp : Defines the exported functions for the DLL.

#include "pch.h"

#include "framework.h"

#include "RawPluginCPlusPlusCode.h"

// This is an example of an exported function.

RAWPLUGINCPLUSPLUSCODE_API int AddTwo(int x, int y)

{

return x + y;

}

Add code to RawPluginCPlusPlusCode.h

// The following ifdef block is the standard way of creating macros which make exporting

// from a DLL simpler. All files within this DLL are compiled with the RAWPLUGINCPLUSPLUSCODE_EXPORTS

// symbol defined on the command line. This symbol should not be defined on any project

// that uses this DLL. This way any other project whose source files include this file see

// RAWPLUGINCPLUSPLUSCODE_API functions as being imported from a DLL, whereas this DLL sees symbols

// defined with this macro as being exported.

#ifdef RAWPLUGINCPLUSPLUSCODE_EXPORTS

#define RAWPLUGINCPLUSPLUSCODE_API __declspec(dllexport)

#else

#define RAWPLUGINCPLUSPLUSCODE_API __declspec(dllimport)

#endif

extern "C" RAWPLUGINCPLUSPLUSCODE_API int AddTwo(int x, int y);

Select ‘Release’ and ‘x64’ configuration in Visual Studio
Select Build menu and press Build Solution
Start Xojo 2019 r1.1
Create a new Desktop project in Windows and save it as RawPlugin.xojo_binary_file
Change the Xojo project to an x64 application
Copy the dll file from C:\Users\Owner\Desktop\New\RawPlugin\RawPluginCPlusPlusCode\x64\Release\ RAWPLUGINCPLUSPLUSCODE.dll and paste it beside the RawPlugin.xojo_binary_file
Add three TextFields to hold two numbers from the user (numbers to be added) and the last Textfield to show the answer.
Add the following code to an action event

Sub Action() Handles Action

Declare Function AddTwo Lib "C:\Users\Owner\Desktop\New\RawPlugin\RAWPLUGINCPLUSPLUSCODE.dll" (x as Integer, y as Integer) As Integer

Dim Answer as Integer

If System.IsFunctionAvailable("AddTwo", "C:\Users\Owner\Desktop\New\RawPlugin\RAWPLUGINCPLUSPLUSCODE.dll") Then

Answer = AddTwo(5, 3) //Add 5 + 3

Answer = AddTwo(TFFirstNumber.Text.CLong, TFSecondNumber.Text.CLong)

Else

Answer = 0 //Error

End If

TFAnswer.Text = Answer.ToText

End Sub

The code can be downloaded at Github Raw Plugin.

Thats it! This program was created in Visual Studio C++ 2019, and Xojo 2019 r1.1 on the 23rd of September 2019.