Extract preview mix pass execution

docs/modernization/debt.md

@@ -201,6 +201,10 @@ agent or engineer to remove them without reconstructing context from chat.
   `execute_legacy_canvas_draw_merge_layer_texture(...)`; per-plane iteration,
   temporary-stroke branch selection, and concrete layer RTT ownership remain in
   the legacy Canvas path.
+- 2026-06-14: DEBT-0036 was narrowed again. `NodeStrokePreview::stroke_draw_mix()`
+  now routes the mix-pass execution request through
+  `make_stroke_draw_mix_execution_request(...)`; the retained path still owns
+  the concrete framebuffer, viewport, and draw ordering.
 - 2026-06-13: DEBT-0036 was narrowed again. `Canvas::draw_merge()` temporary
   composite setup now routes through `execute_canvas_draw_merge_temporary_composite(...)`;
   setup, sampler, texture, draw, and unbind callbacks still remain retained in

docs/modernization/tasks.md

@@ -1870,7 +1870,7 @@ ctest --preset desktop-fast --build-config Debug -R "pp_paint_renderer_stroke_ex
 
 ### STR-041 - Extract Preview Mix Pass Execution Ownership
 
-Status: Ready
+Status: Done
 Score: no score movement
 Debt: `DEBT-0036`
 Scope: `src/node_stroke_preview.cpp`, `tests/paint_renderer/compositor_tests.cpp`
@@ -1881,6 +1881,8 @@ Move the remaining `NodeStrokePreview::stroke_draw_mix()` execution ownership
 into a retained helper so the callsite keeps only the structural mix-pass
 orchestration.
 
+Closeout: `cf859cd4`
+
 Done Checks:
 
 - `NodeStrokePreview::stroke_draw_mix()` no longer owns the mix-pass execution

src/node_stroke_preview.cpp

@@ -514,64 +514,11 @@ void NodeStrokePreview::stroke_draw_mix(const glm::vec2& bb_min, const glm::vec2
         make_stroke_preview_mix_pass_request(*b, m_size));
     gl_state gl;
     [[maybe_unused]] const bool mix_ok = pp::panopainter::execute_legacy_node_stroke_preview_mix_pass(
-        pp::panopainter::LegacyNodeStrokePreviewMixExecutionRequest {
+        make_stroke_draw_mix_execution_request(
-            .shader = mix_pass.shader,
+            mix_pass,
-            .mixer_width = m_rtt_mixer.getWidth(),
+            gl,
-            .mixer_height = m_rtt_mixer.getHeight(),
+            bb_min,
-            .scissor_x = static_cast<int>(bb_min.x),
+            bb_sz));
-            .scissor_y = static_cast<int>(bb_min.y),
-            .scissor_width = static_cast<int>(bb_sz.x),
-            .scissor_height = static_cast<int>(bb_sz.y),
-            .save_state = [&] {
-                gl.save();
-            },
-            .setup_mix_shader = [&](const pp::panopainter::LegacyNodeStrokePreviewMixPassPlan::ShaderPlan& shader_plan) {
-                pp::panopainter::setup_legacy_stroke_composite_shader(
-                    make_stroke_preview_mix_composite_uniforms(shader_plan));
-            },
-            .bind_mixer_framebuffer = [&] {
-                m_rtt_mixer.bindFramebuffer();
-            },
-            .configure_mix_target_state = [&](
-                int mixer_width,
-                int mixer_height,
-                int scissor_x,
-                int scissor_y,
-                int scissor_width,
-                int scissor_height) {
-                apply_stroke_preview_viewport(0, 0, mixer_width, mixer_height);
-                apply_stroke_preview_capability(pp::renderer::gl::depth_test_state(), false);
-                apply_stroke_preview_capability(pp::renderer::gl::scissor_test_state(), true);
-                apply_stroke_preview_capability(pp::renderer::gl::blend_state(), false);
-                apply_stroke_preview_scissor(
-                    scissor_x,
-                    scissor_y,
-                    scissor_width,
-                    scissor_height);
-            },
-            .bind_mix_inputs = [&] {
-                m_sampler_linear.bind(stroke_preview_composite_slots::kBackground);
-                set_active_texture_unit(stroke_preview_composite_slots::kBackground);
-                m_tex_background.bind();
-                set_active_texture_unit(stroke_preview_composite_slots::kStroke);
-                m_rtt.bindTexture();
-                set_active_texture_unit(stroke_preview_composite_slots::kDual);
-                m_tex_dual.bind();
-                set_active_texture_unit(stroke_preview_composite_slots::kPattern);
-                b->m_pattern_texture ?
-                    b->m_pattern_texture->bind() :
-                    unbind_texture_2d();
-            },
-            .draw_mix = [&] {
-                m_plane.draw_fill();
-            },
-            .unbind_mixer_framebuffer = [&] {
-                m_rtt_mixer.unbindFramebuffer();
-            },
-            .restore_state = [&] {
-                gl.restore();
-            },
-        });
     assert(mix_ok);
 }
 
@@ -931,6 +878,73 @@ NodeStrokePreview::make_stroke_draw_immediate_pass_sequence_request(
     };
 }
 
+pp::panopainter::LegacyNodeStrokePreviewMixExecutionRequest
+NodeStrokePreview::make_stroke_draw_mix_execution_request(
+    const pp::panopainter::LegacyNodeStrokePreviewMixPassPlan& mix_pass,
+    gl_state& gl,
+    const glm::vec2& bb_min,
+    const glm::vec2& bb_sz)
+{
+    return pp::panopainter::LegacyNodeStrokePreviewMixExecutionRequest {
+        .shader = mix_pass.shader,
+        .mixer_width = m_rtt_mixer.getWidth(),
+        .mixer_height = m_rtt_mixer.getHeight(),
+        .scissor_x = static_cast<int>(bb_min.x),
+        .scissor_y = static_cast<int>(bb_min.y),
+        .scissor_width = static_cast<int>(bb_sz.x),
+        .scissor_height = static_cast<int>(bb_sz.y),
+        .save_state = [&] {
+            gl.save();
+        },
+        .setup_mix_shader = [&](const pp::panopainter::LegacyNodeStrokePreviewMixPassPlan::ShaderPlan& shader_plan) {
+            pp::panopainter::setup_legacy_stroke_composite_shader(
+                make_stroke_preview_mix_composite_uniforms(shader_plan));
+        },
+        .bind_mixer_framebuffer = [&] {
+            m_rtt_mixer.bindFramebuffer();
+        },
+        .configure_mix_target_state = [&](
+            int mixer_width,
+            int mixer_height,
+            int scissor_x,
+            int scissor_y,
+            int scissor_width,
+            int scissor_height) {
+            apply_stroke_preview_viewport(0, 0, mixer_width, mixer_height);
+            apply_stroke_preview_capability(pp::renderer::gl::depth_test_state(), false);
+            apply_stroke_preview_capability(pp::renderer::gl::scissor_test_state(), true);
+            apply_stroke_preview_capability(pp::renderer::gl::blend_state(), false);
+            apply_stroke_preview_scissor(
+                scissor_x,
+                scissor_y,
+                scissor_width,
+                scissor_height);
+        },
+        .bind_mix_inputs = [&] {
+            m_sampler_linear.bind(stroke_preview_composite_slots::kBackground);
+            set_active_texture_unit(stroke_preview_composite_slots::kBackground);
+            m_tex_background.bind();
+            set_active_texture_unit(stroke_preview_composite_slots::kStroke);
+            m_rtt.bindTexture();
+            set_active_texture_unit(stroke_preview_composite_slots::kDual);
+            m_tex_dual.bind();
+            set_active_texture_unit(stroke_preview_composite_slots::kPattern);
+            m_brush->m_pattern_texture ?
+                m_brush->m_pattern_texture->bind() :
+                unbind_texture_2d();
+        },
+        .draw_mix = [&] {
+            m_plane.draw_fill();
+        },
+        .unbind_mixer_framebuffer = [&] {
+            m_rtt_mixer.unbindFramebuffer();
+        },
+        .restore_state = [&] {
+            gl.restore();
+        },
+    };
+}
+
 Image NodeStrokePreview::render_to_image()
 {
     std::lock_guard<std::mutex> _lock(s_render_mutex);

src/node_stroke_preview.h

@@ -73,6 +73,11 @@ public:
         bool copy_stroke_destination,
         float zoom,
         const glm::vec2& size);
+    pp::panopainter::LegacyNodeStrokePreviewMixExecutionRequest make_stroke_draw_mix_execution_request(
+        const pp::panopainter::LegacyNodeStrokePreviewMixPassPlan& mix_pass,
+        gl_state& gl,
+        const glm::vec2& bb_min,
+        const glm::vec2& bb_sz);
     void draw_stroke();
     void draw_stroke_immediate();
     Image render_to_image();