Route thumbnail and node image texture setup through helpers

docs/modernization/debt.md

@@ -18,6 +18,14 @@ agent or engineer to remove them without reconstructing context from chat.
 
 ## Recent Reductions
 
+- 2026-06-13: DEBT-0036 was narrowed again. `NodeImage` and
+  `NodeImageTexture` retained plain image `Texture` shader setup now routes
+  through `legacy_canvas_draw_merge_services.h`; the nodes still own
+  texture/sampler binding, atlas setup, blend state, and draw execution.
+- 2026-06-13: DEBT-0036 was narrowed again. `Canvas::thumbnail_generate`
+  checkerboard and final `Texture` shader setup now route through
+  `legacy_canvas_draw_merge_services.h`; thumbnail generation still owns
+  destination copies, sampler/texture binding, readback, and draw execution.
 - 2026-06-13: DEBT-0036 was narrowed again. `Canvas::draw_objects` retained
   object composite `Texture` shader setup now routes through
   `legacy_canvas_draw_merge_services.h`; draw_objects still owns temporary

docs/modernization/roadmap.md

@@ -3021,6 +3021,10 @@ Results:
   stroke composite shader setup helper, while render-task ordering, framebuffer
   copy bounds, sampler/texture binding, and draw execution remain in retained
   canvas-mode code.
+- `Canvas::thumbnail_generate` checkerboard redraw and final texture blending
+  now share the retained draw-merge shader setup helpers, while destination
+  copies, sampler/texture binding, readback, and draw execution remain in
+  retained Canvas code.
 - `Canvas::draw_objects` retained object compositing now shares the retained
   draw-merge texture shader setup helper, while temporary face readback,
   sampler/texture binding, draw execution, and dirty-box updates remain in
@@ -3032,6 +3036,10 @@ Results:
   draw-merge shader setup helper for per-layer `TextureBlend` uniforms, while
   destination feedback copies, sampler/texture binding, grid redraw, readback,
   and draw execution remain in retained Canvas code.
+- `NodeImage` and `NodeImageTexture` retained plain image drawing now share the
+  retained draw-merge texture shader setup helper for `Texture`, `Tex`, and
+  `MVP` setup. Texture/sampler binding, atlas setup, blend state, and draw
+  execution remain in the node paths.
 - `Canvas::stroke_draw_mix` now shares the retained stroke composite shader
   helper for mixer-pass `CompDraw` setup, while preserving its caller-specific
   texture slot uniforms. Mixer framebuffer/scissor state, sampler and texture

src/canvas.cpp

@@ -3031,15 +3031,19 @@ Image Canvas::thumbnail_generate(int w, int h)
             copy_framebuffer_to_texture_2d(0, 0, 0, 0, w, h);
 
             // draw the grid
-            ShaderManager::use(kShader::Checkerboard);
-            ShaderManager::u_mat4(kShaderUniform::MVP, plane_mvp);
+            pp::panopainter::setup_legacy_canvas_draw_merge_checkerboard_shader(
+                pp::panopainter::LegacyCanvasDrawMergeCheckerboardUniforms {
+                    .mvp = plane_mvp,
+                });
             m_face_plane.draw_fill();
 
             // now blend with the background
             apply_canvas_capability(blend_state(), true);
-            ShaderManager::use(kShader::Texture);
-            ShaderManager::u_int(kShaderUniform::Tex, 0);
-            ShaderManager::u_mat4(kShaderUniform::MVP, glm::ortho(-.5f, .5f, -.5f, .5f, -1.f, 1.f));
+            pp::panopainter::setup_legacy_canvas_draw_merge_texture_shader(
+                pp::panopainter::LegacyCanvasDrawMergeTextureUniforms {
+                    .mvp = glm::ortho(-.5f, .5f, -.5f, .5f, -1.f, 1.f),
+                    .texture_slot = 0,
+                });
             m_sampler.bind(0); // linear
             m_plane.draw_fill();
 

src/node_image.cpp

@@ -1,4 +1,5 @@
 #include "pch.h"
+#include "legacy_canvas_draw_merge_services.h"
 #include "log.h"
 #include "legacy_ui_gl_dispatch.h"
 #include "node_image.h"
@@ -109,13 +110,14 @@ void NodeImage::draw()
         ShaderManager::use(kShader::Atlas);
         ShaderManager::u_vec2(kShaderUniform::Tof, m_off);
         ShaderManager::u_vec2(kShaderUniform::Tsz, m_sz);
+        ShaderManager::u_int(kShaderUniform::Tex, 0);
+        ShaderManager::u_mat4(kShaderUniform::MVP, m_mvp * glm::scale(glm::vec3(m_scale, 1.f)));
     }
     else
     {
-        ShaderManager::use(kShader::Texture);
+        pp::panopainter::setup_legacy_canvas_draw_merge_texture_shader(
+            {.mvp = m_mvp * glm::scale(glm::vec3(m_scale, 1.f)), .texture_slot = 0});
     }
-    ShaderManager::u_int(kShaderUniform::Tex, 0);
-    ShaderManager::u_mat4(kShaderUniform::MVP, m_mvp * glm::scale(glm::vec3(m_scale, 1.f)));
     m_plane.draw_fill();
     sampler.unbind();
     pp::legacy::ui_gl::set_blend_enabled(false, "NodeImage");

src/node_image_texture.cpp

@@ -1,4 +1,5 @@
 #include "pch.h"
+#include "legacy_canvas_draw_merge_services.h"
 #include "log.h"
 #include "legacy_ui_gl_dispatch.h"
 #include "node_image_texture.h"
@@ -23,9 +24,7 @@ void NodeImageTexture::draw()
     auto& sampler = tex && tex->has_mips ? NodeImage::m_sampler_mips : NodeImage::m_sampler;
     sampler.bind(0);
     pp::legacy::ui_gl::set_blend_enabled(true, "NodeImageTexture");
-    ShaderManager::use(kShader::Texture);
-    ShaderManager::u_int(kShaderUniform::Tex, 0);
-    ShaderManager::u_mat4(kShaderUniform::MVP, m_mvp);
+    pp::panopainter::setup_legacy_canvas_draw_merge_texture_shader({.mvp = m_mvp, .texture_slot = 0});
     NodeImage::m_plane.draw_fill();
     sampler.unbind();
     pp::legacy::ui_gl::set_blend_enabled(false, "NodeImageTexture");