Move Win32 async context ownership and trim canvas draw setup

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,