Move Win32 async context ownership and trim canvas draw setup

docs/modernization/debt.md

@@ -18,6 +18,17 @@ agent or engineer to remove them without reconstructing context from chat.
 
 ## Reductions
 
+- 2026-06-16: `DEBT-0003` was narrowed again. The Win32 async GL/context lock
+  state now lives in `src/platform_windows/windows_platform_services.cpp`
+  instead of `src/main.cpp` retained state, and `main.cpp` only seeds the
+  created `HDC`/`HGLRC` into that platform-owned helper during initialization
+  and context recreation; broader Win32 bootstrap/runtime ownership remains.
+- 2026-06-16: `DEBT-0036` was narrowed again. `NodeCanvas` merged-path
+  per-plane merged-texture draw callback setup now routes through
+  `make_legacy_canvas_draw_merge_layer_texture_draw(...)` in
+  `src/legacy_canvas_draw_merge_services.h` instead of keeping that callback
+  setup inline in `NodeCanvas::draw()`; broader canvas draw orchestration and
+  retained GL resource ownership remain.
 - 2026-06-16: `DEBT-0037` was narrowed again. `App::rec_loop()` in
   `src/app.cpp` now delegates recording worker iteration orchestration into
   `process_legacy_recording_worker_iteration(...)` in

docs/modernization/roadmap.md

@@ -117,9 +117,9 @@ Current architecture mismatches that must be treated as real blockers:
   checkerboard background setup now route through retained draw-merge helpers,
   with the cache-to-screen checkerboard-plane callback setup also reduced and
   the merged-path checkerboard background-plane callback plus per-plane
-  merged-texture draw plus the smoothing-mask face shader/draw pass plus
-  heightmap, current-mode, and grid-mode callback setup now routed through the
-  same retained helper family.
+  merged-texture draw callback plus the smoothing-mask face shader/draw pass
+  plus heightmap, current-mode, and grid-mode callback setup now routed
+  through the same retained helper family.
 - `app_layout.cpp` and `app_dialogs.cpp` are still mixed shell/controller files
   rather than thin composition/binding surfaces.
 - `App`, `Canvas`, `Node`, retained workers, and platform entrypoints still use
@@ -135,13 +135,15 @@ Current architecture mismatches that must be treated as real blockers:
   coordination flags now use `std::atomic` instead of unsynchronized globals,
   while the main Win32 entrypoint now groups window/GL/task/VR state behind a
   retained local state object instead of separate process-wide globals, the
-  canvas async worker now sits behind a named retained local worker-state
-  helper instead of a bare static accessor, the prepared-file worker and the
-  canvas async import/export/save/open worker now live under `AppRuntime`
-  instead of retained static app-events/canvas workers, and `App::rec_loop()`
-  now delegates worker-iteration orchestration into the retained recording
-  bridge even though that retained recording path still owns the worker-side
-  readback flow.
+  Win32 async GL/context lock state now lives under
+  `src/platform_windows/windows_platform_services.cpp` instead of `main.cpp`
+  retained state, the canvas async worker now sits behind a named retained
+  local worker-state helper instead of a bare static accessor, the
+  prepared-file worker and the canvas async import/export/save/open worker now
+  live under `AppRuntime` instead of retained static app-events/canvas
+  workers, and `App::rec_loop()` now delegates worker-iteration orchestration
+  into the retained recording bridge even though that retained recording path
+  still owns the worker-side readback flow.
 - Modern C++23 usage exists in extracted components, especially `std::span`,
   explicit result/status objects, and a few concepts, but the live app still
   does not consistently express ownership, thread affinity, or renderer

docs/modernization/tasks.md

@@ -155,6 +155,10 @@ Current slice:
   through `make_legacy_canvas_draw_merge_background_checkerboard_plane(...)`,
   but the node still owns broader live layer traversal and renderer-state
   sequencing.
+- `NodeCanvas` merged-path per-plane merged-texture draw callback setup now
+  also routes through `make_legacy_canvas_draw_merge_layer_texture_draw(...)`,
+  but the node still owns broader live layer traversal and renderer-state
+  sequencing.
 - `NodeCanvas` smoothing-mask face shader setup plus per-face draw execution
   now also route through
   `execute_legacy_canvas_draw_merge_smask_faces(...)`, but the node still owns
@@ -356,6 +360,10 @@ Current slice:
 - `main.cpp` Win32 window handles, GL task/mutex state, splash-dialog state,
   stylus timers, and VR worker state now sit behind one retained local state
   object instead of separate file-scope globals
+- Win32 async GL/context lock state now lives in
+  `src/platform_windows/windows_platform_services.cpp` instead of `main.cpp`
+  retained state, and `main.cpp` only seeds that platform-owned context handle
+  pair during initialization and context recreation
 - prepared-file background work now runs through an `AppRuntime`-owned worker
   queue instead of a retained static worker in `src/app_events.cpp`
 - canvas async import/export/save/open background work now also runs through an

src/legacy_canvas_draw_merge_services.h

@@ -494,6 +494,45 @@ inline void execute_legacy_canvas_draw_merge_layer_texture(
     execution.unbind_layer_texture();
 }
 
+template <typename LayerMergeT, typename SamplerT, typename FacePlaneT, typename SetActiveTextureUnit, typename PlaneTransform>
+[[nodiscard]] inline auto make_legacy_canvas_draw_merge_layer_texture_draw(
+    LayerMergeT* layer_merge,
+    SamplerT* sampler,
+    FacePlaneT* face_plane,
+    SetActiveTextureUnit set_active_texture_unit,
+    glm::mat4 proj,
+    glm::mat4 camera,
+    PlaneTransform plane_transform)
+{
+    return [layer_merge, sampler, face_plane, set_active_texture_unit, proj, camera, plane_transform](int plane_index) {
+        const auto mvp = proj * camera *
+            plane_transform[plane_index] *
+            glm::translate(glm::vec3(0, 0, -1));
+        execute_legacy_canvas_draw_merge_layer_texture(
+            {
+                .mvp = mvp,
+                .texture_slot = 0,
+                .alpha = 1.f,
+                .highlight = false,
+            },
+            {
+                .bind_sampler = [sampler, set_active_texture_unit] {
+                    sampler->bind(0);
+                    set_active_texture_unit(0);
+                },
+                .bind_layer_texture = [layer_merge, plane_index] {
+                    layer_merge->rtt(plane_index).bindTexture();
+                },
+                .draw = [face_plane] {
+                    face_plane->draw_fill();
+                },
+                .unbind_layer_texture = [layer_merge, plane_index] {
+                    layer_merge->rtt(plane_index).unbindTexture();
+                },
+            });
+    };
+}
+
 inline void execute_legacy_canvas_draw_merge_layer_composite(
     bool is_temporary_erase,
     bool is_temporary_paint,

src/main.cpp

@@ -38,21 +38,22 @@
 #define WM_USER_WAKEUP (WM_USER + 2)
 
 LRESULT CALLBACK WndProc(HWND hWnd, UINT msg, WPARAM wp, LPARAM lp);
+namespace pp::platform::windows {
+    void set_async_render_context(HDC hdc, HGLRC hrc);
+    void lock_async_render_context();
+    bool try_lock_async_render_context();
+    void unlock_async_render_context();
+    void swap_async_render_context();
+}
 struct RetainedState
 {
     HINSTANCE hInst{};
     HWND hWnd{};
-    HDC hDC{};
-    HGLRC hRC{};
     const wchar_t* className{};
     bool keys[256]{};
-    std::mutex gl_mutex;
-    std::mutex async_mutex;
-    std::thread::id gl_thread{};
     std::map<kKey, int> vkey_map;
     wchar_t window_title[512]{};
     std::jthread hmd_renderer;
-    int gl_count = 0;
     std::deque<std::packaged_task<void()>> main_tasklist;
     std::mutex main_task_mutex;
     float timer_stylus = 0;
@@ -170,57 +171,22 @@ void destroy_window()
 
 void async_lock()
 {
-    //std::lock_guard<std::mutex> _lock(async_mutex);
-    auto& state = retained_state();
-    if (state.gl_count == 0 || state.gl_thread != std::this_thread::get_id())
-    {
-        state.gl_mutex.lock();
-        bool ret = wglMakeCurrent(state.hDC, state.hRC);
-        if (ret == false)
-            LOG("FAILED wglMakeCurrent: %s", GetLastErrorAsString().c_str());
-        state.gl_thread = std::this_thread::get_id();
-        //LOG("lock");
-    }
-    state.gl_count++;
-    //assert(ret == true);
+    pp::platform::windows::lock_async_render_context();
 }
 
 bool async_lock_try()
 {
-    //std::lock_guard<std::mutex> _lock(async_mutex);
-    auto& state = retained_state();
-    if (state.gl_count == 0 || state.gl_thread != std::this_thread::get_id())
-    {
-        if (!state.gl_mutex.try_lock())
-            return false;
-        bool ret = wglMakeCurrent(state.hDC, state.hRC);
-        if (ret == false)
-            LOG("FAILED wglMakeCurrent: %s", GetLastErrorAsString().c_str());
-        state.gl_thread = std::this_thread::get_id();
-        //LOG("lock");
-    }
-    state.gl_count++;
-    //assert(ret == true);
-    return true;
+    return pp::platform::windows::try_lock_async_render_context();
 }
 
 void win32_async_swap()
 {
-    SwapBuffers(retained_state().hDC);
-    //LOG("swap");
+    pp::platform::windows::swap_async_render_context();
 }
 
 void async_unlock()
 {
-    //std::lock_guard<std::mutex> _lock(async_mutex);
-    auto& state = retained_state();
-    state.gl_count--;
-    if (state.gl_count == 0)
-    {
-        //LOG("unlock");
-        wglMakeCurrent(0, 0);
-        state.gl_mutex.unlock();
-    }
+    pp::platform::windows::unlock_async_render_context();
 }
 
 void win32_update_stylus(float dt)
@@ -866,11 +832,12 @@ int main(int argc, char** argv)
     pfd.cDepthBits = 24;
     pfd.iLayerType = PFD_MAIN_PLANE;
 
-    state.hDC = GetDC(state.hWnd);
-    int pxfmt = ChoosePixelFormat(state.hDC, &pfd);
-    SetPixelFormat(state.hDC, pxfmt, &pfd);
-    state.hRC = wglCreateContext(state.hDC); // Create OpenGL 2.1 or less
-    wglMakeCurrent(state.hDC, state.hRC);
+    HDC hDC = GetDC(state.hWnd);
+    int pxfmt = ChoosePixelFormat(hDC, &pfd);
+    SetPixelFormat(hDC, pxfmt, &pfd);
+    HGLRC hRC = wglCreateContext(hDC); // Create OpenGL 2.1 or less
+    wglMakeCurrent(hDC, hRC);
+    pp::platform::windows::set_async_render_context(hDC, hRC);
 
     // Initialize extensions
     if (!gladLoadGL())
@@ -878,7 +845,7 @@ int main(int argc, char** argv)
         LOG("gladLoadGL() failed");
         return 0;
     }
-    if (!gladLoadWGL(state.hDC))
+    if (!gladLoadWGL(hDC))
     {
         LOG("gladLoadWGL() failed");
         return 0;
@@ -912,18 +879,19 @@ int main(int argc, char** argv)
         UINT numFormat;
 
         wglMakeCurrent(NULL, NULL);
-        wglDeleteContext(state.hRC);
+        wglDeleteContext(hRC);
         DestroyWindow(state.hWnd);
 
         state.hWnd = CreateWindow(wc.lpszClassName, state.window_title, wnd_style, clientPos.x, clientPos.y,
             (float)(clientRect.right - clientRect.left),
             (float)(clientRect.bottom - clientRect.top), 0, 0, state.hInst, 0);
 
-        state.hDC = GetDC(state.hWnd);
-        wglChoosePixelFormatARB(state.hDC, wgl_config.pixel_format_attributes.data(), nullptr, 1, &pxfmt, &numFormat);
-        SetPixelFormat(state.hDC, pxfmt, &pfd);
-        state.hRC = wglCreateContextAttribsARB(state.hDC, NULL, wgl_config.context_attributes.data());
-        wglMakeCurrent(state.hDC, state.hRC);
+        hDC = GetDC(state.hWnd);
+        wglChoosePixelFormatARB(hDC, wgl_config.pixel_format_attributes.data(), nullptr, 1, &pxfmt, &numFormat);
+        SetPixelFormat(hDC, pxfmt, &pfd);
+        hRC = wglCreateContextAttribsARB(hDC, NULL, wgl_config.context_attributes.data());
+        wglMakeCurrent(hDC, hRC);
+        pp::platform::windows::set_async_render_context(hDC, hRC);
     }
     else
     {

src/node_canvas.cpp

@@ -385,32 +385,14 @@ void NodeCanvas::draw()
                     }),
             });
 
-        const auto draw_merged_texture_plane = [&](int plane_index) {
-            pp::panopainter::execute_legacy_canvas_draw_merge_layer_texture(
-                {
-                    .mvp = proj * camera *
-                        m_canvas->m_plane_transform[plane_index] *
-                        glm::translate(glm::vec3(0, 0, -1)),
-                    .texture_slot = 0,
-                    .alpha = 1.f,
-                    .highlight = false,
-                },
-                {
-                    .bind_sampler = [&] {
-                        m_sampler.bind(0);
-                        set_active_texture_unit(0);
-                    },
-                    .bind_layer_texture = [&] {
-                        m_canvas->m_layers_merge.rtt(plane_index).bindTexture();
-                    },
-                    .draw = [&] {
-                        m_face_plane.draw_fill();
-                    },
-                    .unbind_layer_texture = [&] {
-                        m_canvas->m_layers_merge.rtt(plane_index).unbindTexture();
-                    },
-                });
-        };
+        const auto draw_merged_texture_plane = pp::panopainter::make_legacy_canvas_draw_merge_layer_texture_draw(
+            &m_canvas->m_layers_merge,
+            &m_sampler,
+            &m_face_plane,
+            set_active_texture_unit,
+            proj,
+            camera,
+            m_canvas->m_plane_transform);
 
         for (int plane_index = 0; plane_index < 6; plane_index++)
         {

src/platform_windows/windows_platform_services.cpp

@@ -26,6 +26,84 @@ void win32_update_stylus(float dt);
 void win32_save_window_state();
 bool win32_vr_start();
 void win32_vr_stop();
+std::string GetLastErrorAsString();
+
+namespace pp::platform::windows {
+
+namespace {
+
+struct RetainedWin32AsyncRenderContextState final {
+    HDC hdc{};
+    HGLRC hrc{};
+    std::mutex gl_mutex;
+    std::thread::id gl_thread{};
+    int gl_count = 0;
+};
+
+[[nodiscard]] RetainedWin32AsyncRenderContextState& retained_win32_async_render_context_state()
+{
+    static RetainedWin32AsyncRenderContextState state;
+    return state;
+}
+
+}
+
+void set_async_render_context(HDC hdc, HGLRC hrc)
+{
+    auto& state = retained_win32_async_render_context_state();
+    state.hdc = hdc;
+    state.hrc = hrc;
+    state.gl_thread = {};
+    state.gl_count = 0;
+}
+
+void lock_async_render_context()
+{
+    auto& state = retained_win32_async_render_context_state();
+    if (state.gl_count == 0 || state.gl_thread != std::this_thread::get_id())
+    {
+        state.gl_mutex.lock();
+        const bool ret = wglMakeCurrent(state.hdc, state.hrc);
+        if (!ret)
+            LOG("FAILED wglMakeCurrent: %s", GetLastErrorAsString().c_str());
+        state.gl_thread = std::this_thread::get_id();
+    }
+    state.gl_count++;
+}
+
+bool try_lock_async_render_context()
+{
+    auto& state = retained_win32_async_render_context_state();
+    if (state.gl_count == 0 || state.gl_thread != std::this_thread::get_id())
+    {
+        if (!state.gl_mutex.try_lock())
+            return false;
+        const bool ret = wglMakeCurrent(state.hdc, state.hrc);
+        if (!ret)
+            LOG("FAILED wglMakeCurrent: %s", GetLastErrorAsString().c_str());
+        state.gl_thread = std::this_thread::get_id();
+    }
+    state.gl_count++;
+    return true;
+}
+
+void unlock_async_render_context()
+{
+    auto& state = retained_win32_async_render_context_state();
+    state.gl_count--;
+    if (state.gl_count == 0)
+    {
+        wglMakeCurrent(0, 0);
+        state.gl_mutex.unlock();
+    }
+}
+
+void swap_async_render_context()
+{
+    SwapBuffers(retained_win32_async_render_context_state().hdc);
+}
+
+}
 
 namespace {