Contain XCUI ImGui adapters behind explicit host seams

new_editor/src/XCUIBackend/ImGuiXCUIInputSource.h

@@ -0,0 +1,56 @@
+#pragma once
+
+#include "XCUIBackend/ImGuiXCUIInputAdapter.h"
+
+namespace XCEngine {
+namespace Editor {
+namespace XCUIBackend {
+
+class ImGuiXCUIInputSnapshotSource final : public IXCUIInputSnapshotSource {
+public:
+    explicit ImGuiXCUIInputSnapshotSource(const ImGuiIO* io = nullptr)
+        : m_io(io) {
+    }
+
+    void SetIO(const ImGuiIO* io) {
+        m_io = io;
+    }
+
+    const ImGuiIO* GetIO() const {
+        return ResolveIO();
+    }
+
+    XCUIInputBridgeFrameSnapshot CaptureSnapshot(
+        const XCUIInputBridgeCaptureOptions& options = XCUIInputBridgeCaptureOptions()) const override {
+        const ImGuiIO* io = ResolveIO();
+        return io != nullptr
+            ? ImGuiXCUIInputAdapter::CaptureSnapshot(*io, options)
+            : XCUIInputBridgeFrameSnapshot();
+    }
+
+    const ::XCEngine::UI::UIPoint& GetPointerPosition() const override {
+        m_cachedPointerPosition = {};
+        const ImGuiIO* io = ResolveIO();
+        if (io != nullptr) {
+            m_cachedPointerPosition = ::XCEngine::UI::UIPoint(io->MousePos.x, io->MousePos.y);
+        }
+
+        return m_cachedPointerPosition;
+    }
+
+private:
+    const ImGuiIO* ResolveIO() const {
+        if (m_io != nullptr) {
+            return m_io;
+        }
+
+        return ImGui::GetCurrentContext() != nullptr ? &ImGui::GetIO() : nullptr;
+    }
+
+    const ImGuiIO* m_io = nullptr;
+    mutable ::XCEngine::UI::UIPoint m_cachedPointerPosition = {};
+};
+
+} // namespace XCUIBackend
+} // namespace Editor
+} // namespace XCEngine