rive-flutter/example/windows/runner/flutter_window.cpp

#include "flutter_window.h"

#include <optional>

#include "flutter/generated_plugin_registrant.h"

FlutterWindow::FlutterWindow(const flutter::DartProject& project) :
    project_(project)
{}

FlutterWindow::~FlutterWindow() {}

bool FlutterWindow::OnCreate()
{
    if (!Win32Window::OnCreate())
    {
        return false;
    }

    RECT frame = GetClientArea();

    // The size here must match the window dimensions to avoid unnecessary
    // surface creation / destruction in the startup path.
    flutter_controller_ = std::make_unique<flutter::FlutterViewController>(
        frame.right - frame.left,
        frame.bottom - frame.top,
        project_);
    // Ensure that basic setup of the controller was successful.
    if (!flutter_controller_->engine() || !flutter_controller_->view())
    {
        return false;
    }
    RegisterPlugins(flutter_controller_->engine());
    SetChildContent(flutter_controller_->view()->GetNativeWindow());
    return true;
}

void FlutterWindow::OnDestroy()
{
    if (flutter_controller_)
    {
        flutter_controller_ = nullptr;
    }

    Win32Window::OnDestroy();
}

LRESULT
FlutterWindow::MessageHandler(HWND hwnd,
                              UINT const message,
                              WPARAM const wparam,
                              LPARAM const lparam) noexcept
{
    // Give Flutter, including plugins, an opportunity to handle window
    // messages.
    if (flutter_controller_)
    {
        std::optional<LRESULT> result =
            flutter_controller_->HandleTopLevelWindowProc(hwnd,
                                                          message,
                                                          wparam,
                                                          lparam);
        if (result)
        {
            return *result;
        }
    }

    switch (message)
    {
        case WM_FONTCHANGE:
            flutter_controller_->engine()->ReloadSystemFonts();
            break;
    }

    return Win32Window::MessageHandler(hwnd, message, wparam, lparam);
}