win32

#define UNICODE
#define _UNICODE

#include <tchar.h>
#include <windows.h>
#include <windowsx.h>
#include <commctrl.h>
#include <richedit.h>

// Code::Block doesn't have a tom.h :(
// https://github.com/kinke/mingw-w64-crt/blob/master/mingw-w64-headers/include/tom.h
#include "tom.h" 
#include <richole.h>
#include <unknwn.h>

#pragma comment(lib,"Comctl32.lib")

IUnknown* tr_code = NULL;
ITextDocument* td_code;

#define DEFINE_GUIDXXX(name, l, w1, w2, b1, b2, b3, b4, b5, b6, b7, b8) EXTERN_C const GUID name = { l, w1, w2, { b1, b2,  b3,  b4,  b5,  b6,  b7,  b8 } }
DEFINE_GUIDXXX(IID_ITextDocument, 0x8CC497C0, 0xA1DF, 0x11CE, 0x80, 0x98, 0x00, 0xAA, 0x00, 0x47, 0xBE, 0x5D);

#define IDC_EDITOR 1000
#define IDC_BUTTON 1001

HWND hEditorWnd;

bool updateHighlighting(HWND hWnd) {
    int carriagePos = 0;
    SendMessage(hWnd, EM_GETSEL, (WPARAM)&carriagePos, (WPARAM)&carriagePos);

    CHARFORMAT cf = { 0 };
    cf.cbSize = sizeof(CHARFORMAT);
    cf.dwMask = CFM_COLOR | CFM_BOLD;
    cf.crTextColor = RGB(0, 0, 200);
    cf.dwEffects = CFM_BOLD;
    SendMessage(hWnd, EM_SETSEL, 0, -1);
    SendMessage(hWnd, EM_SETCHARFORMAT, SCF_SELECTION, (LPARAM)&cf);

    cf.dwMask = CFM_COLOR | CFM_BOLD;
    cf.dwEffects = cf.dwEffects & ~CFM_BOLD;
    cf.crTextColor = RGB(200, 0, 0);
    SendMessage(hWnd, EM_SETSEL, 4, 6);

    SendMessage(hWnd, EM_SETCHARFORMAT, SCF_SELECTION, (LPARAM)&cf);
    SendMessage(hWnd, EM_SETSEL, carriagePos, carriagePos);

    _tprintf(TEXT("End highlight
"));
    return true;
}

LRESULT CALLBACK WindowProcedure(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam) {
    switch (msg) {
    case WM_DESTROY:
        PostQuitMessage(0);
        break;

    case WM_COMMAND: {
        if (LOWORD(wParam) == IDC_BUTTON && HIWORD(wParam) == BN_CLICKED)
            _tprintf(TEXT("UNDO: can %i => result: %i
"), Edit_CanUndo(hEditorWnd), Edit_Undo(hEditorWnd));

        if (LOWORD(wParam) == IDC_EDITOR && HIWORD(wParam) == EN_CHANGE) {
            td_code->Undo(tomSuspend, NULL); // <---
            updateHighlighting(hEditorWnd);
            td_code->Undo(tomResume, NULL); // <---
            return 1;
        }

    }
                   break;

    default:
        return DefWindowProc(hWnd, msg, wParam, lParam);
    }

    return 0;
}

int WINAPI WinMain(HINSTANCE hThisInstance, HINSTANCE hPrevInstance, LPSTR lpszArgument, int nCmdShow) {
    InitCommonControls();
    LoadLibrary(TEXT("msftedit.dll"));

    HWND hWnd;
    MSG msg;
    WNDCLASSEX wincl;

    wincl.hInstance = hThisInstance;
    wincl.lpszClassName = TEXT("AppClass");
    wincl.lpfnWndProc = WindowProcedure;
    wincl.style = CS_DBLCLKS;
    wincl.cbSize = sizeof(WNDCLASSEX);
    wincl.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wincl.hIconSm = LoadIcon(NULL, IDI_APPLICATION);
    wincl.hCursor = LoadCursor(NULL, IDC_ARROW);
    wincl.lpszMenuName = NULL;
    wincl.cbClsExtra = 0;
    wincl.cbWndExtra = 0;
    wincl.hbrBackground = (HBRUSH)COLOR_BACKGROUND;

    if (!RegisterClassEx(&wincl))
        return 0;

    hWnd = CreateWindowEx(0, TEXT("AppClass"), TEXT("Test"), WS_OVERLAPPEDWINDOW | WS_VISIBLE, 300, 400, 310, 375, HWND_DESKTOP, NULL, hThisInstance, NULL);

    CreateWindowEx(0, WC_BUTTON, L"UNDO", WS_VISIBLE | WS_CHILD | WS_TABSTOP, 10, 310, 280, 30, hWnd, (HMENU)IDC_BUTTON, hThisInstance, NULL);
    hEditorWnd = CreateWindowEx(0, TEXT("RICHEDIT50W"), NULL, WS_VISIBLE | WS_CHILD | ES_MULTILINE | ES_AUTOVSCROLL | ES_AUTOHSCROLL | ES_WANTRETURN | WS_VSCROLL | WS_HSCROLL | WS_TABSTOP | ES_NOHIDESEL, 0, 0, 300, 300, hWnd, (HMENU)IDC_EDITOR, hThisInstance, NULL);
    SendMessage(hEditorWnd, EM_SETEVENTMASK, 0, ENM_CHANGE | ENM_UPDATE | ENM_KEYEVENTS);

    // /   
    SendMessage(hEditorWnd, EM_GETOLEINTERFACE, 0, (LPARAM)&tr_code);
    if (tr_code == (IRichEditOle*)NULL) {
        MessageBox(0, TEXT("Error when trying to get RichEdit OLE Object"), NULL, 0);
        return 0;
    }
    tr_code->QueryInterface(IID_ITextDocument, (void**)&td_code);
    // /    

    while (GetMessage(&msg, NULL, 0, 0)) {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    return msg.wParam;
}