Route stroke pad planning through helper

docs/modernization/debt.md

@@ -18,6 +18,10 @@ agent or engineer to remove them without reconstructing context from chat.
 
 ## Recent Reductions
 
+- 2026-06-13: DEBT-0036 was narrowed again. `Canvas::stroke_draw` pad-region
+  planning now routes through the retained stroke execution helper wrapping
+  `pp_paint_renderer`; pad color selection, dirty-face iteration,
+  framebuffer copies, quad upload, and draw execution remain retained.
 - 2026-06-13: DEBT-0036 was narrowed again. `Canvas::stroke_draw` face
   dirty-box planning now routes through a retained stroke execution helper
   wrapping `pp_paint_renderer`, retained stroke commit step dispatch clamps

docs/modernization/roadmap.md

@@ -3079,6 +3079,10 @@ Results:
   compositor coverage now includes malformed retained commit plans plus
   all-input stroke-preview composite planning. Live stroke rasterization,
   callback execution, texture binding, and history mutation remain retained.
+- `Canvas::stroke_draw` pad-region planning now shares the retained stroke
+  execution helper wrapping `pp_paint_renderer`, while pad color selection,
+  dirty-face iteration, framebuffer copies, quad upload, and draw execution
+  remain retained.
 - Remaining simple color, hue, color-quad, grid heightmap, and pen/line
   preview shader setup in UI nodes and canvas modes now shares retained helper
   surfaces, while geometry, texture/sampler binding, blend/depth state,

src/canvas.cpp

@@ -95,21 +95,6 @@ pp::renderer::Extent2D canvas_stroke_extent(int width, int height) noexcept
     };
 }
 
-pp::paint_renderer::CanvasStrokeBox canvas_stroke_box(glm::vec4 box) noexcept
-{
-    return pp::paint_renderer::CanvasStrokeBox {
-        .min_x = box.x,
-        .min_y = box.y,
-        .max_x = box.z,
-        .max_y = box.w,
-    };
-}
-
-glm::vec4 glm_box(pp::paint_renderer::CanvasStrokeBox box) noexcept
-{
-    return glm::vec4(box.min_x, box.min_y, box.max_x, box.max_y);
-}
-
 pp::paint_renderer::CanvasBlendGatePlan draw_merge_blend_gate_plan(
     int width,
     int height,
@@ -822,10 +807,10 @@ void Canvas::stroke_draw()
     {
         if (!box_dirty[i])
             continue;
-        const auto pad_region = pp::paint_renderer::plan_canvas_stroke_pad_region(
-            pp::paint_renderer::CanvasStrokePadRegionRequest {
+        const auto pad_region = pp::panopainter::plan_legacy_canvas_stroke_pad_region(
+            pp::panopainter::LegacyCanvasStrokePadRegionRequest {
                 .extent = stroke_extent,
-                .pass_dirty_box = canvas_stroke_box(box_face[i]),
+                .pass_dirty_box = box_face[i],
             });
         if (!pad_region.has_pixels)
             continue;

src/legacy_canvas_stroke_execution_services.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include "paint_renderer/compositor.h"
+#include "../libs/glm/glm/glm.hpp"
 #include "util.h"
 
 #include <array>
@@ -46,6 +47,17 @@ struct LegacyCanvasStrokeFaceDirtyResult {
     bool pass_dirty = false;
 };
 
+struct LegacyCanvasStrokePadRegionRequest {
+    pp::renderer::Extent2D extent {};
+    glm::vec4 pass_dirty_box {};
+};
+
+struct LegacyCanvasStrokePadRegionResult {
+    bool has_pixels = false;
+    pp::paint_renderer::CanvasStrokeCopyRegion copy_region {};
+    std::array<pp::paint_renderer::CanvasStrokePoint, 6> ndc_quad {};
+};
+
 [[nodiscard]] inline pp::paint_renderer::CanvasStrokeBox legacy_canvas_stroke_box(glm::vec4 box) noexcept
 {
     return pp::paint_renderer::CanvasStrokeBox {
@@ -62,6 +74,22 @@ struct LegacyCanvasStrokeFaceDirtyResult {
     return glm::vec4(box.min_x, box.min_y, box.max_x, box.max_y);
 }
 
+[[nodiscard]] inline LegacyCanvasStrokePadRegionResult plan_legacy_canvas_stroke_pad_region(
+    const LegacyCanvasStrokePadRegionRequest& request) noexcept
+{
+    const auto plan = pp::paint_renderer::plan_canvas_stroke_pad_region(
+        pp::paint_renderer::CanvasStrokePadRegionRequest {
+            .extent = request.extent,
+            .pass_dirty_box = legacy_canvas_stroke_box(request.pass_dirty_box),
+        });
+
+    return LegacyCanvasStrokePadRegionResult {
+        .has_pixels = plan.has_pixels,
+        .copy_region = plan.copy_region,
+        .ndc_quad = plan.ndc_quad,
+    };
+}
+
 [[nodiscard]] inline LegacyCanvasStrokeFaceDirtyResult plan_legacy_canvas_stroke_face_dirty_update(
     const LegacyCanvasStrokeFaceDirtyRequest& request) noexcept
 {