XCEngine/new_editor/app/Platform/Win32/WindowManager/TabDrag.cpp

#include "Platform/Win32/EditorWindowManager.h"

#include "Platform/Win32/WindowManager/CrossWindowDropInternal.h"
#include "State/EditorContext.h"
#include "Platform/Win32/EditorWindow.h"

#include <algorithm>
#include <cmath>

namespace XCEngine::UI::Editor::App {

namespace {

using Win32::Internal::CrossWindowDockDropTarget;
using Win32::Internal::TryResolveCrossWindowDockDropTarget;

constexpr LONG kFallbackDragHotspotX = 40;
constexpr LONG kFallbackDragHotspotY = 12;

POINT BuildFallbackGlobalTabDragHotspot() {
    POINT hotspot = {};
    hotspot.x = kFallbackDragHotspotX;
    hotspot.y = kFallbackDragHotspotY;
    return hotspot;
}

float ResolveWindowDpiScale(HWND hwnd) {
    if (hwnd == nullptr) {
        return 1.0f;
    }

    const UINT dpi = GetDpiForWindow(hwnd);
    return dpi == 0u ? 1.0f : static_cast<float>(dpi) / 96.0f;
}

} // namespace

bool EditorWindowManager::IsGlobalTabDragActive() const {
    return m_globalTabDragSession.active;
}

bool EditorWindowManager::OwnsActiveGlobalTabDrag(std::string_view windowId) const {
    return m_globalTabDragSession.active &&
        m_globalTabDragSession.panelWindowId == windowId;
}

void EditorWindowManager::BeginGlobalTabDragSession(
    std::string_view panelWindowId,
    std::string_view sourceNodeId,
    std::string_view panelId,
    const POINT& screenPoint,
    const POINT& dragHotspot) {
    m_globalTabDragSession.active = true;
    m_globalTabDragSession.panelWindowId = std::string(panelWindowId);
    m_globalTabDragSession.sourceNodeId = std::string(sourceNodeId);
    m_globalTabDragSession.panelId = std::string(panelId);
    m_globalTabDragSession.screenPoint = screenPoint;
    m_globalTabDragSession.dragHotspot = dragHotspot;
}

bool EditorWindowManager::TryResolveGlobalTabDragHotspot(
    const EditorWindow& sourceWindow,
    std::string_view nodeId,
    std::string_view panelId,
    const POINT& screenPoint,
    POINT& outDragHotspot) const {
    const HWND hwnd = sourceWindow.GetHwnd();
    if (hwnd == nullptr) {
        return false;
    }

    const auto& layout =
        sourceWindow.GetShellFrame().workspaceInteractionFrame.dockHostFrame.layout;
    for (const Widgets::UIEditorDockHostTabStackLayout& tabStack : layout.tabStacks) {
        if (tabStack.nodeId != nodeId) {
            continue;
        }

        const std::size_t tabCount =
            (std::min)(tabStack.items.size(), tabStack.tabStripLayout.tabHeaderRects.size());
        for (std::size_t index = 0u; index < tabCount; ++index) {
            if (tabStack.items[index].panelId != panelId) {
                continue;
            }

            const ::XCEngine::UI::UIPoint clientPointDips =
                sourceWindow.ConvertScreenPixelsToClientDips(screenPoint);
            const ::XCEngine::UI::UIRect& tabRect =
                tabStack.tabStripLayout.tabHeaderRects[index];
            const float dpiScale = ResolveWindowDpiScale(hwnd);
            const float localOffsetXDips = (std::clamp)(
                clientPointDips.x - tabRect.x,
                0.0f,
                (std::max)(tabRect.width, 0.0f));
            const float localOffsetYDips = (std::clamp)(
                clientPointDips.y - tabRect.y,
                0.0f,
                (std::max)(tabRect.height, 0.0f));
            outDragHotspot.x = static_cast<LONG>(std::lround(localOffsetXDips * dpiScale));
            outDragHotspot.y = static_cast<LONG>(std::lround(localOffsetYDips * dpiScale));
            return true;
        }
    }

    return false;
}

void EditorWindowManager::UpdateGlobalTabDragOwnerWindowPosition() {
    if (!m_globalTabDragSession.active) {
        return;
    }

    EditorWindow* ownerWindow = FindWindow(m_globalTabDragSession.panelWindowId);
    if (ownerWindow == nullptr || ownerWindow->GetHwnd() == nullptr) {
        return;
    }

    RECT windowRect = {};
    if (!GetWindowRect(ownerWindow->GetHwnd(), &windowRect)) {
        return;
    }

    const LONG targetLeft =
        m_globalTabDragSession.screenPoint.x - m_globalTabDragSession.dragHotspot.x;
    const LONG targetTop =
        m_globalTabDragSession.screenPoint.y - m_globalTabDragSession.dragHotspot.y;
    if (windowRect.left == targetLeft && windowRect.top == targetTop) {
        return;
    }

    SetWindowPos(
        ownerWindow->GetHwnd(),
        nullptr,
        targetLeft,
        targetTop,
        0,
        0,
        SWP_NOSIZE | SWP_NOZORDER | SWP_NOACTIVATE);
}

void EditorWindowManager::ClearGlobalTabDragDropPreview() {
    if (m_globalTabDragSession.previewWindowId.empty()) {
        return;
    }

    if (EditorWindow* previewWindow = FindWindow(m_globalTabDragSession.previewWindowId);
        previewWindow != nullptr) {
        previewWindow->ClearExternalDockHostDropPreview();
        previewWindow->InvalidateHostWindow();
    }
    m_globalTabDragSession.previewWindowId.clear();
}

void EditorWindowManager::UpdateGlobalTabDragDropPreview() {
    if (!m_globalTabDragSession.active) {
        return;
    }

    EditorWindow* targetWindow = FindTopmostWindowAtScreenPoint(
        m_globalTabDragSession.screenPoint,
        m_globalTabDragSession.panelWindowId);
    if (targetWindow == nullptr || targetWindow->GetHwnd() == nullptr) {
        ClearGlobalTabDragDropPreview();
        return;
    }

    const ::XCEngine::UI::UIPoint targetPoint =
        targetWindow->ConvertScreenPixelsToClientDips(m_globalTabDragSession.screenPoint);
    const Widgets::UIEditorDockHostLayout& targetLayout =
        targetWindow->GetShellFrame().workspaceInteractionFrame.dockHostFrame.layout;
    CrossWindowDockDropTarget dropTarget = {};
    if (!TryResolveCrossWindowDockDropTarget(targetLayout, targetPoint, dropTarget) ||
        !dropTarget.valid) {
        ClearGlobalTabDragDropPreview();
        return;
    }

    if (!m_globalTabDragSession.previewWindowId.empty() &&
        m_globalTabDragSession.previewWindowId != targetWindow->GetWindowId()) {
        ClearGlobalTabDragDropPreview();
    }

    Widgets::UIEditorDockHostDropPreviewState preview = {};
    preview.visible = true;
    preview.sourceNodeId = m_globalTabDragSession.sourceNodeId;
    preview.sourcePanelId = m_globalTabDragSession.panelId;
    preview.targetNodeId = dropTarget.nodeId;
    preview.placement = dropTarget.placement;
    preview.insertionIndex = dropTarget.insertionIndex;
    targetWindow->SetExternalDockHostDropPreview(preview);
    targetWindow->InvalidateHostWindow();
    m_globalTabDragSession.previewWindowId = std::string(targetWindow->GetWindowId());
}

void EditorWindowManager::EndGlobalTabDragSession() {
    if (!m_globalTabDragSession.active) {
        return;
    }

    ClearGlobalTabDragDropPreview();

    if (EditorWindow* ownerWindow = FindWindow(m_globalTabDragSession.panelWindowId);
        ownerWindow != nullptr) {
        if (GetCapture() == ownerWindow->GetHwnd()) {
            ReleaseCapture();
        }
        ownerWindow->ResetInteractionState();
    }

    m_globalTabDragSession = {};
}

bool EditorWindowManager::HandleGlobalTabDragPointerMove(HWND hwnd) {
    if (!m_globalTabDragSession.active) {
        return false;
    }

    const EditorWindow* ownerWindow = FindWindow(m_globalTabDragSession.panelWindowId);
    if (ownerWindow == nullptr || ownerWindow->GetHwnd() != hwnd) {
        return false;
    }

    POINT screenPoint = {};
    if (GetCursorPos(&screenPoint)) {
        m_globalTabDragSession.screenPoint = screenPoint;
        UpdateGlobalTabDragOwnerWindowPosition();
        UpdateGlobalTabDragDropPreview();
    }
    return true;
}

void EditorWindowManager::ProcessPendingGlobalTabDragStarts() {
    if (m_globalTabDragSession.active) {
        return;
    }

    for (const std::unique_ptr<EditorWindow>& window : m_windows) {
        if (window == nullptr || window->GetHwnd() == nullptr) {
            continue;
        }

        if (TryStartGlobalTabDrag(*window)) {
            return;
        }
    }
}

bool EditorWindowManager::TryStartGlobalTabDrag(EditorWindow& sourceWindow) {
    const std::optional<EditorWindowPendingTabDragStart> pending =
        sourceWindow.ConsumePendingTabDragStart();
    if (!pending.has_value()) {
        return false;
    }

    POINT dragHotspot = BuildFallbackGlobalTabDragHotspot();
    TryResolveGlobalTabDragHotspot(
        sourceWindow,
        pending->nodeId,
        pending->panelId,
        pending->screenPoint,
        dragHotspot);

    if (sourceWindow.IsPrimary()) {
        UIEditorWindowWorkspaceController windowWorkspaceController =
            BuildLiveWindowWorkspaceController(sourceWindow.GetWindowId());
        const UIEditorWindowWorkspaceOperationResult result =
            windowWorkspaceController.DetachPanelToNewWindow(
                sourceWindow.GetWindowId(),
                pending->nodeId,
                pending->panelId);
        if (result.status != UIEditorWindowWorkspaceOperationStatus::Changed) {
            LogRuntimeTrace(
                "drag",
                "failed to start global tab drag from primary window: " + result.message);
            return false;
        }

        if (!SynchronizeWindowsFromController(
                windowWorkspaceController,
                result.targetWindowId,
                pending->screenPoint)) {
            LogRuntimeTrace("drag", "failed to synchronize detached drag window state");
            return false;
        }

        EditorWindow* detachedWindow = FindWindow(result.targetWindowId);
        if (detachedWindow == nullptr || detachedWindow->GetHwnd() == nullptr) {
            LogRuntimeTrace("drag", "detached drag window was not created.");
            return false;
        }

        BeginGlobalTabDragSession(
            detachedWindow->GetWindowId(),
            detachedWindow->GetWorkspaceController().GetWorkspace().root.nodeId,
            pending->panelId,
            pending->screenPoint,
            dragHotspot);
        UpdateGlobalTabDragOwnerWindowPosition();
        SetCapture(detachedWindow->GetHwnd());
        SetForegroundWindow(detachedWindow->GetHwnd());
        LogRuntimeTrace(
            "drag",
            "started global tab drag by detaching panel '" + pending->panelId +
                "' into window '" + std::string(detachedWindow->GetWindowId()) + "'");
        return true;
    }

    sourceWindow.ResetInteractionState();
    BeginGlobalTabDragSession(
        sourceWindow.GetWindowId(),
        pending->nodeId,
        pending->panelId,
        pending->screenPoint,
        dragHotspot);
    UpdateGlobalTabDragOwnerWindowPosition();
    if (sourceWindow.GetHwnd() != nullptr) {
        SetCapture(sourceWindow.GetHwnd());
    }
    LogRuntimeTrace(
        "drag",
        "started global tab drag from detached window '" +
            std::string(sourceWindow.GetWindowId()) +
            "' panel '" + pending->panelId + "'");
    return true;
}

} // namespace XCEngine::UI::Editor::App