Remove backend probing from XCUI panel canvas host

docs/plan/XCUI_Phase_Status_2026-04-05.md

@@ -46,6 +46,7 @@ Old `editor` replacement is explicitly out of scope for this phase.
   - `XCUIShellChromeState` no longer carries the legacy host demo-window toggle or command id on the generic shell-state surface
   - `Application.h` no longer exposes that legacy demo command through generic `ShellCommandIds`, `ShellCommandBindings`, or `RegisterShellViewCommands(...)`
   - the legacy demo window toggle now lives as a compatibility-only command inside `ApplicationLegacyImGui.cpp`
+  - `Application.h` now also uses backend-neutral compatibility-host naming for the non-native window-host path, so the generic application header no longer names `LegacyImGui` in its mode enum or private host-frame method declarations
   - generic `Application` host-mode/member naming is now also shifting from `LegacyImGui` toward `CompatibilityHost`, so the default shell surface does not have to encode ImGui into every host-facing method name
 - Old `editor` replacement remains deferred; all active execution still stays inside XCUI shared code and `new_editor`.
 
@@ -109,7 +110,7 @@ Current gap:
 - `new_editor` now also has an isolated `XCUIEditorCommandRouter` model with shortcut matching, enable predicates, and direct command invocation semantics covered by dedicated tests, ready for shell-frame integration.
 - `XCUI Demo` now exports pending per-frame command ids through `DrainPendingCommandIds()`, so editor-side hosts have a clean seam for observing demo/runtime command traffic without parsing draw data.
 - `XCUI Demo` and `LayoutLab` panel canvases are now being pulled behind a dedicated `IXCUIPanelCanvasHost` seam, so canvas surface presentation, hover/focus fallback state, and overlay draw hooks no longer have to stay hard-coded inside each ImGui panel implementation.
-- The panel-canvas seam now also exposes explicit backend/capability metadata and a minimal `NullXCUIPanelCanvasHost`, so non-ImGui host paths have a concrete placeholder backend instead of relying on an implicit ImGui default.
+- The panel-canvas seam now keeps the generic host contract on observable canvas behavior only; backend/capability identity probing has been removed from `IXCUIPanelCanvasHost`, and the minimal `NullXCUIPanelCanvasHost` remains the concrete placeholder host for non-ImGui paths.
 - `XCUI Demo` and `LayoutLab` panel input now also flows through an explicit `IXCUIInputSnapshotSource` seam, so panel/runtime code no longer reads `ImGuiIO` / `ImGui::IsKeyPressed` / `ImGui::IsMouseClicked` directly when the shell wants to use an ImGui adapter.
 - `new_editor` now also has an explicit `ImGuiXCUIInputSnapshotSource` adapter, keeping ImGui-specific input capture in the host adapter layer instead of inside panel/runtime update code.
 - Panel diagnostics were expanded to clearly separate preview/runtime/input state and native vs legacy paths.
@@ -265,7 +266,7 @@ Current gap:
 - `new_editor` now also has a pure `XCUIShellChromeState` model with dedicated tests, covering shell panel visibility, hosted-preview mode, and shell view toggles without depending on ImGui or `Application`.
 - `XCUIShellChromeState` now also exposes effective hosted-preview state helpers and shell view-toggle command-id helpers, so shell routing code no longer has to manually combine enablement and requested preview mode.
 - `XCUIShellChromeState` hosted-preview modes were renamed away from `LegacyImGui`, so XCUI shell state no longer treats ImGui as the generic fallback concept.
-- The panel-canvas seam now has dedicated null/imgui backend coverage, including explicit backend/capability reporting and a non-ImGui placeholder host path for future native shell adoption.
+- The panel-canvas seam now has dedicated null/compat/native coverage around stable debug names, passive-session safety, externally driven native snapshots, and compat-host factory creation without relying on explicit backend/capability reporting.
 - The native host follow-up is now present in `new_editor`:
   - `NativeWindowUICompositor` provides a swapchain-native XCUI packet present path beside the legacy ImGui compositor
   - `Application` now defaults to that native host path and directly composes `XCUI Demo` plus `Layout Lab` into one native shell frame

new_editor/src/XCUIBackend/ImGuiXCUIPanelCanvasHost.h

@@ -89,18 +89,6 @@ public:
         return "ImGuiXCUIPanelCanvasHost";
     }
 
-    XCUIPanelCanvasHostBackend GetBackend() const override {
-        return XCUIPanelCanvasHostBackend::ImGui;
-    }
-
-    XCUIPanelCanvasHostCapabilities GetCapabilities() const override {
-        XCUIPanelCanvasHostCapabilities capabilities = {};
-        capabilities.supportsPointerHitTesting = true;
-        capabilities.supportsHostedSurfaceImages = true;
-        capabilities.supportsPrimitiveOverlays = true;
-        return capabilities;
-    }
-
     XCUIPanelCanvasSession BeginCanvas(const XCUIPanelCanvasRequest& request) override {
         const char* childId =
             request.childId != nullptr && request.childId[0] != '\0'

new_editor/src/XCUIBackend/NativeXCUIPanelCanvasHost.h

@@ -132,18 +132,6 @@ public:
         return "NativeXCUIPanelCanvasHost";
     }
 
-    XCUIPanelCanvasHostBackend GetBackend() const override {
-        return XCUIPanelCanvasHostBackend::Native;
-    }
-
-    XCUIPanelCanvasHostCapabilities GetCapabilities() const override {
-        XCUIPanelCanvasHostCapabilities capabilities = {};
-        capabilities.supportsHostedSurfaceImages = true;
-        capabilities.supportsPrimitiveOverlays = true;
-        capabilities.supportsExternallyDrivenSession = true;
-        return capabilities;
-    }
-
     void SetCanvasSession(const XCUIPanelCanvasSession& session) {
         m_configuredSession = session;
         m_hasConfiguredSession = true;

new_editor/src/XCUIBackend/NullXCUIPanelCanvasHost.h

@@ -14,14 +14,6 @@ public:
         return "NullXCUIPanelCanvasHost";
     }
 
-    XCUIPanelCanvasHostBackend GetBackend() const override {
-        return XCUIPanelCanvasHostBackend::Null;
-    }
-
-    XCUIPanelCanvasHostCapabilities GetCapabilities() const override {
-        return {};
-    }
-
     XCUIPanelCanvasSession BeginCanvas(const XCUIPanelCanvasRequest& request) override {
         m_canvasSession = BuildPassiveXCUIPanelCanvasSession(request);
         return m_canvasSession;

new_editor/src/XCUIBackend/XCUIPanelCanvasHost.h

@@ -4,7 +4,6 @@
 
 #include <XCEngine/UI/DrawData.h>
 
-#include <cstdint>
 #include <memory>
 #include <string>
 #include <string_view>
@@ -13,19 +12,6 @@ namespace XCEngine {
 namespace Editor {
 namespace XCUIBackend {
 
-enum class XCUIPanelCanvasHostBackend : std::uint8_t {
-    Null = 0,
-    ImGui,
-    Native
-};
-
-struct XCUIPanelCanvasHostCapabilities {
-    bool supportsPointerHitTesting = false;
-    bool supportsHostedSurfaceImages = false;
-    bool supportsPrimitiveOverlays = false;
-    bool supportsExternallyDrivenSession = false;
-};
-
 struct XCUIPanelCanvasRequest {
     const char* childId = nullptr;
     float height = 0.0f;
@@ -98,8 +84,6 @@ public:
     virtual ~IXCUIPanelCanvasHost() = default;
 
     virtual const char* GetDebugName() const = 0;
-    virtual XCUIPanelCanvasHostBackend GetBackend() const = 0;
-    virtual XCUIPanelCanvasHostCapabilities GetCapabilities() const = 0;
     virtual XCUIPanelCanvasSession BeginCanvas(const XCUIPanelCanvasRequest& request) = 0;
     virtual void DrawFilledRect(
         const ::XCEngine::UI::UIRect& rect,

tests/NewEditor/test_imgui_xcui_panel_canvas_host.cpp

@@ -6,20 +6,12 @@ namespace {
 
 using XCEngine::Editor::XCUIBackend::CreateImGuiXCUIPanelCanvasHost;
 using XCEngine::Editor::XCUIBackend::IXCUIPanelCanvasHost;
-using XCEngine::Editor::XCUIBackend::XCUIPanelCanvasHostBackend;
-using XCEngine::Editor::XCUIBackend::XCUIPanelCanvasHostCapabilities;
 
-TEST(NewEditorImGuiXCUIPanelCanvasHostTest, ReportsExplicitBackendAndCapabilities) {
+TEST(NewEditorImGuiXCUIPanelCanvasHostTest, FactoryCreatesCompatCanvasHostWithStableDebugName) {
     std::unique_ptr<IXCUIPanelCanvasHost> host = CreateImGuiXCUIPanelCanvasHost();
     ASSERT_NE(host, nullptr);
 
     EXPECT_STREQ(host->GetDebugName(), "ImGuiXCUIPanelCanvasHost");
-    EXPECT_EQ(host->GetBackend(), XCUIPanelCanvasHostBackend::ImGui);
-
-    const XCUIPanelCanvasHostCapabilities capabilities = host->GetCapabilities();
-    EXPECT_TRUE(capabilities.supportsPointerHitTesting);
-    EXPECT_TRUE(capabilities.supportsHostedSurfaceImages);
-    EXPECT_TRUE(capabilities.supportsPrimitiveOverlays);
 }
 
 } // namespace

tests/NewEditor/test_legacy_imgui_host_interop.cpp

@@ -12,7 +12,6 @@ using XCEngine::Editor::XCUIBackend::CreateLegacyImGuiHostedPreviewPresenter;
 using XCEngine::Editor::XCUIBackend::CreateLegacyImGuiPanelCanvasHost;
 using XCEngine::Editor::XCUIBackend::CreateLegacyImGuiWindowUICompositor;
 using XCEngine::Editor::XCUIBackend::RenderLegacyImGuiDemoWindow;
-using XCEngine::Editor::XCUIBackend::XCUIPanelCanvasHostBackend;
 using XCEngine::Editor::XCUIBackend::XCUIInputBridgeFrameSnapshot;
 
 class ScopedImGuiContext final {
@@ -30,7 +29,7 @@ public:
     ScopedImGuiContext& operator=(const ScopedImGuiContext&) = delete;
 };
 
-TEST(LegacyImGuiHostInteropTest, CreatesLegacyHostAdaptersWithImGuiBackends) {
+TEST(LegacyImGuiHostInteropTest, CreatesLegacyHostAdaptersWithExpectedDebugNames) {
     auto compositor = CreateLegacyImGuiWindowUICompositor();
     auto presenter = CreateLegacyImGuiHostedPreviewPresenter();
     auto canvasHost = CreateLegacyImGuiPanelCanvasHost();
@@ -38,12 +37,7 @@ TEST(LegacyImGuiHostInteropTest, CreatesLegacyHostAdaptersWithImGuiBackends) {
     ASSERT_NE(compositor, nullptr);
     ASSERT_NE(presenter, nullptr);
     ASSERT_NE(canvasHost, nullptr);
-    EXPECT_EQ(canvasHost->GetBackend(), XCUIPanelCanvasHostBackend::ImGui);
-
-    const auto capabilities = canvasHost->GetCapabilities();
-    EXPECT_TRUE(capabilities.supportsPointerHitTesting);
-    EXPECT_TRUE(capabilities.supportsHostedSurfaceImages);
-    EXPECT_TRUE(capabilities.supportsPrimitiveOverlays);
+    EXPECT_STREQ(canvasHost->GetDebugName(), "ImGuiXCUIPanelCanvasHost");
 }
 
 TEST(LegacyImGuiHostInteropTest, ApplyInputCaptureCopiesImGuiIoFlagsIntoSnapshot) {

tests/NewEditor/test_native_xcui_panel_canvas_host.cpp

@@ -8,8 +8,6 @@ using XCEngine::Editor::XCUIBackend::CreateNativeXCUIPanelCanvasHost;
 using XCEngine::Editor::XCUIBackend::IXCUIPanelCanvasHost;
 using XCEngine::Editor::XCUIBackend::NativeXCUIPanelCanvasHost;
 using XCEngine::Editor::XCUIBackend::XCUIPanelCanvasFrameSnapshot;
-using XCEngine::Editor::XCUIBackend::XCUIPanelCanvasHostBackend;
-using XCEngine::Editor::XCUIBackend::XCUIPanelCanvasHostCapabilities;
 using XCEngine::Editor::XCUIBackend::XCUIPanelCanvasRequest;
 using XCEngine::Editor::XCUIBackend::XCUIPanelCanvasSession;
 
@@ -22,18 +20,11 @@ XCEngine::UI::UITextureHandle MakeSurfaceTextureHandle(std::uintptr_t nativeHand
     return texture;
 }
 
-TEST(NativeXCUIPanelCanvasHostTest, FactoryReportsNativeBackendCapabilitiesAndNoSnapshotBeforeBegin) {
+TEST(NativeXCUIPanelCanvasHostTest, FactoryCreatesHostWithStableDebugNameAndNoSnapshotBeforeBegin) {
     std::unique_ptr<IXCUIPanelCanvasHost> host = CreateNativeXCUIPanelCanvasHost();
     ASSERT_NE(host, nullptr);
 
     EXPECT_STREQ(host->GetDebugName(), "NativeXCUIPanelCanvasHost");
-    EXPECT_EQ(host->GetBackend(), XCUIPanelCanvasHostBackend::Native);
-
-    const XCUIPanelCanvasHostCapabilities capabilities = host->GetCapabilities();
-    EXPECT_FALSE(capabilities.supportsPointerHitTesting);
-    EXPECT_TRUE(capabilities.supportsHostedSurfaceImages);
-    EXPECT_TRUE(capabilities.supportsPrimitiveOverlays);
-    EXPECT_TRUE(capabilities.supportsExternallyDrivenSession);
 
     XCUIPanelCanvasFrameSnapshot snapshot = {};
     EXPECT_FALSE(host->TryGetLatestFrameSnapshot(snapshot));

tests/NewEditor/test_xcui_demo_panel.cpp

@@ -87,14 +87,6 @@ public:
         return "StubCanvasHost";
     }
 
-    XCEngine::Editor::XCUIBackend::XCUIPanelCanvasHostBackend GetBackend() const override {
-        return XCEngine::Editor::XCUIBackend::XCUIPanelCanvasHostBackend::Null;
-    }
-
-    XCEngine::Editor::XCUIBackend::XCUIPanelCanvasHostCapabilities GetCapabilities() const override {
-        return {};
-    }
-
     XCUIPanelCanvasSession BeginCanvas(const XCUIPanelCanvasRequest& request) override {
         lastRequest = request;
         ++beginCanvasCallCount;

tests/NewEditor/test_xcui_layout_lab_panel.cpp

@@ -69,14 +69,6 @@ public:
         return "StubCanvasHost";
     }
 
-    XCEngine::Editor::XCUIBackend::XCUIPanelCanvasHostBackend GetBackend() const override {
-        return XCEngine::Editor::XCUIBackend::XCUIPanelCanvasHostBackend::Null;
-    }
-
-    XCEngine::Editor::XCUIBackend::XCUIPanelCanvasHostCapabilities GetCapabilities() const override {
-        return {};
-    }
-
     XCUIPanelCanvasSession BeginCanvas(const XCUIPanelCanvasRequest&) override {
         return m_session;
     }

tests/NewEditor/test_xcui_panel_canvas_host.cpp

@@ -8,22 +8,22 @@ using XCEngine::Editor::XCUIBackend::CreateNullXCUIPanelCanvasHost;
 using XCEngine::Editor::XCUIBackend::BuildPassiveXCUIPanelCanvasSession;
 using XCEngine::Editor::XCUIBackend::IXCUIPanelCanvasHost;
 using XCEngine::Editor::XCUIBackend::ResolveXCUIPanelCanvasChildId;
-using XCEngine::Editor::XCUIBackend::XCUIPanelCanvasHostBackend;
-using XCEngine::Editor::XCUIBackend::XCUIPanelCanvasHostCapabilities;
 using XCEngine::Editor::XCUIBackend::XCUIPanelCanvasRequest;
 using XCEngine::Editor::XCUIBackend::XCUIPanelCanvasSession;
 
-TEST(NewEditorXCUIPanelCanvasHostTest, NullHostReportsExplicitBackendAndCapabilities) {
+TEST(NewEditorXCUIPanelCanvasHostTest, NullHostProvidesStableDebugNameAndSafePassiveSessions) {
     std::unique_ptr<IXCUIPanelCanvasHost> host = CreateNullXCUIPanelCanvasHost();
     ASSERT_NE(host, nullptr);
 
     EXPECT_STREQ(host->GetDebugName(), "NullXCUIPanelCanvasHost");
-    EXPECT_EQ(host->GetBackend(), XCUIPanelCanvasHostBackend::Null);
 
-    const XCUIPanelCanvasHostCapabilities capabilities = host->GetCapabilities();
-    EXPECT_FALSE(capabilities.supportsPointerHitTesting);
-    EXPECT_FALSE(capabilities.supportsHostedSurfaceImages);
-    EXPECT_FALSE(capabilities.supportsPrimitiveOverlays);
+    const XCUIPanelCanvasSession session = host->BeginCanvas({});
+    EXPECT_FALSE(session.validCanvas);
+    EXPECT_FALSE(session.hovered);
+    EXPECT_FALSE(session.windowFocused);
+    EXPECT_FLOAT_EQ(session.hostRect.width, 0.0f);
+    EXPECT_FLOAT_EQ(session.hostRect.height, 0.0f);
+    host->EndCanvas();
 }
 
 TEST(NewEditorXCUIPanelCanvasHostTest, ResolveChildIdFallsBackToStableDefaultForMissingNames) {