terminal/src/cascadia/WindowsTerminal/AppHost.cpp

// Copyright (c) Microsoft Corporation.
// Licensed under the MIT license.

#include "pch.h"
#include "AppHost.h"
#include "../types/inc/Viewport.hpp"
#include "../types/inc/utils.hpp"

using namespace winrt::Windows::UI;
using namespace winrt::Windows::UI::Composition;
using namespace winrt::Windows::UI::Xaml;
using namespace winrt::Windows::UI::Xaml::Hosting;
using namespace winrt::Windows::Foundation::Numerics;
using namespace ::Microsoft::Console;
using namespace ::Microsoft::Console::Types;

AppHost::AppHost() noexcept :
    _app{},
    _window{ nullptr }
{
    _useNonClientArea = _app.GetShowTabsInTitlebar();

    if (_useNonClientArea)
    {
        _window = std::make_unique<NonClientIslandWindow>();
    }
    else
    {
        _window = std::make_unique<IslandWindow>();
    }

    // Tell the window to callback to us when it's about to handle a WM_CREATE
    auto pfn = std::bind(&AppHost::_HandleCreateWindow,
                         this,
                         std::placeholders::_1,
                         std::placeholders::_2);
    _window->SetCreateCallback(pfn);

    _window->MakeWindow();
}

AppHost::~AppHost()
{
    // destruction order is important for proper teardown here
    _window = nullptr;
    _app.Close();
    _app = nullptr;
}

// Method Description:
// - Initializes the XAML island, creates the terminal app, and sets the
//   island's content to that of the terminal app's content. Also registers some
//   callbacks with TermApp.
// !!! IMPORTANT!!!
// This must be called *AFTER* WindowsXamlManager::InitializeForCurrentThread.
// If it isn't, then we won't be able to create the XAML island.
// Arguments:
// - <none>
// Return Value:
// - <none>
void AppHost::Initialize()
{
    _window->Initialize();

    if (_useNonClientArea)
    {
        // Register our callbar for when the app's non-client content changes.
        // This has to be done _before_ App::Create, as the app might set the
        // content in Create.
        _app.SetTitleBarContent({ this, &AppHost::_UpdateTitleBarContent });
    }
    _app.RequestedThemeChanged({ this, &AppHost::_UpdateTheme });

    _app.Create();

    _app.TitleChanged({ this, &AppHost::AppTitleChanged });
    _app.LastTabClosed({ this, &AppHost::LastTabClosed });

    AppTitleChanged(_app.GetTitle());

    // Set up the content of the application. If the app has a custom titlebar,
    // set that content as well.
    _window->SetContent(_app.GetRoot());
    _window->OnAppInitialized();
}

// Method Description:
// - Called when the app's title changes. Fires off a window message so we can
//   update the window's title on the main thread.
// Arguments:
// - newTitle: the string to use as the new window title
// Return Value:
// - <none>
void AppHost::AppTitleChanged(winrt::hstring newTitle)
{
    _window->UpdateTitle(newTitle.c_str());
}

// Method Description:
// - Called when no tab is remaining to close the window.
// Arguments:
// - <none>
// Return Value:
// - <none>
void AppHost::LastTabClosed()
{
    _window->Close();
}

// Method Description:
// - Resize the window we're about to create to the appropriate dimensions, as
//   specified in the settings. This will be called during the handling of
//   WM_CREATE. We'll load the settings for the app, then get the proposed size
//   of the terminal from the app. Using that proposed size, we'll resize the
//   window we're creating, so that it'll match the values in the settings.
// Arguments:
// - hwnd: The HWND of the window we're about to create.
// - proposedRect: The location and size of the window that we're about to
//   create. We'll use this rect to determine which monitor the window is about
//   to appear on.
// Return Value:
// - <none>
void AppHost::_HandleCreateWindow(const HWND hwnd, const RECT proposedRect)
{
    // Find nearest montitor.
    HMONITOR hmon = MonitorFromRect(&proposedRect, MONITOR_DEFAULTTONEAREST);

    // This API guarantees that dpix and dpiy will be equal, but neither is an
    // optional parameter so give two UINTs.
    UINT dpix = USER_DEFAULT_SCREEN_DPI;
    UINT dpiy = USER_DEFAULT_SCREEN_DPI;
    // If this fails, we'll use the default of 96.
    GetDpiForMonitor(hmon, MDT_EFFECTIVE_DPI, &dpix, &dpiy);

    auto initialSize = _app.GetLaunchDimensions(dpix);

    const short _currentWidth = Utils::ClampToShortMax(
        static_cast<long>(ceil(initialSize.X)), 1);
    const short _currentHeight = Utils::ClampToShortMax(
        static_cast<long>(ceil(initialSize.Y)), 1);

    // Create a RECT from our requested client size
    auto nonClient = Viewport::FromDimensions({ _currentWidth,
                                                _currentHeight })
                         .ToRect();

    // Get the size of a window we'd need to host that client rect. This will
    // add the titlebar space.
    if (_useNonClientArea)
    {
        // If we're in NC tabs mode, do the math ourselves. Get the margins
        // we're using for the window - this will include the size of the
        // titlebar content.
        auto pNcWindow = static_cast<NonClientIslandWindow*>(_window.get());
        const MARGINS margins = pNcWindow->GetFrameMargins();
        nonClient.left = 0;
        nonClient.top = 0;
        nonClient.right = margins.cxLeftWidth + nonClient.right + margins.cxRightWidth;
        nonClient.bottom = margins.cyTopHeight + nonClient.bottom + margins.cyBottomHeight;
    }
    else
    {
        bool succeeded = AdjustWindowRectExForDpi(&nonClient, WS_OVERLAPPEDWINDOW, false, 0, dpix);
        if (!succeeded)
        {
            // If we failed to get the correct window size for whatever reason, log
            // the error and go on. We'll use whatever the control proposed as the
            // size of our window, which will be at least close.
            LOG_LAST_ERROR();
            nonClient = Viewport::FromDimensions({ _currentWidth,
                                                   _currentHeight })
                            .ToRect();
        }
    }

    const auto adjustedHeight = nonClient.bottom - nonClient.top;
    const auto adjustedWidth = nonClient.right - nonClient.left;

    const COORD origin{ gsl::narrow<short>(proposedRect.left),
                        gsl::narrow<short>(proposedRect.top) };
    const COORD dimensions{ Utils::ClampToShortMax(adjustedWidth, 1),
                            Utils::ClampToShortMax(adjustedHeight, 1) };

    const auto newPos = Viewport::FromDimensions(origin, dimensions);

    bool succeeded = SetWindowPos(hwnd,
                                  nullptr,
                                  newPos.Left(),
                                  newPos.Top(),
                                  newPos.Width(),
                                  newPos.Height(),
                                  SWP_NOACTIVATE | SWP_NOZORDER);

    // If we can't resize the window, that's really okay. We can just go on with
    // the originally proposed window size.
    LOG_LAST_ERROR_IF(!succeeded);
}

// Method Description:
// - Called when the app wants to set its titlebar content. We'll take the
//   UIElement and set the Content property of our Titlebar that element.
// Arguments:
// - sender: unused
// - arg: the UIElement to use as the new Titlebar content.
// Return Value:
// - <none>
void AppHost::_UpdateTitleBarContent(const winrt::TerminalApp::App&, const winrt::Windows::UI::Xaml::UIElement& arg)
{
    if (_useNonClientArea)
    {
        (static_cast<NonClientIslandWindow*>(_window.get()))->SetTitlebarContent(arg);
    }
}

// Method Description:
// - Called when the app wants to change its theme. We'll forward this to the
//   IslandWindow, so it can update the root UI element of the entire XAML tree.
// Arguments:
// - sender: unused
// - arg: the ElementTheme to use as the new theme for the UI
// Return Value:
// - <none>
void AppHost::_UpdateTheme(const winrt::TerminalApp::App&, const winrt::Windows::UI::Xaml::ElementTheme& arg)
{
    _window->UpdateTheme(arg);
}