Route texture alpha setup through helper

docs/modernization/debt.md

@@ -18,6 +18,12 @@ agent or engineer to remove them without reconstructing context from chat.
 
 ## Recent Reductions
 
+- 2026-06-13: DEBT-0036 was narrowed again. Retained `TextureAlpha` shader
+  setup now routes through `legacy_canvas_draw_merge_services.h` for Canvas
+  draw-merge layer redraws, depth export merged-layer rendering, NodeCanvas
+  cached/live layer redraws, and desktop VR layer redraws; those paths still
+  own sampler/texture binding, render-task ordering, per-frame alpha updates,
+  and draw execution.
 - 2026-06-13: DEBT-0036 was narrowed again. `NodeCanvas` density-resolve and
   desktop VR UI `Texture` shader setup now route through
   `legacy_canvas_draw_merge_services.h`; those paths still own render target,

docs/modernization/roadmap.md

@@ -3051,6 +3051,11 @@ Results:
   share the retained draw-merge texture shader setup helper for `Texture`,
   `Tex`, and `MVP` setup. Texture/sampler binding, viewport/state setup, and
   draw execution remain in the node paths.
+- Retained `TextureAlpha` setup now shares the draw-merge shader setup helper
+  for Canvas draw-merge layer redraws, depth export merged-layer rendering,
+  NodeCanvas cached/live layer redraws, and desktop VR layer redraws, while
+  sampler/texture binding, render-task ordering, per-frame alpha updates, and
+  draw execution remain in retained code.
 - `NodeCanvas` density-resolve drawing and desktop VR UI drawing now share the
   retained draw-merge texture shader setup helper, while render target,
   sampler/texture binding, viewport/state restoration, and draw execution

src/app_vr.cpp

@@ -398,11 +398,13 @@ void App::vr_draw(const glm::mat4& proj, const glm::mat4& camera, const glm::mat
             else
             {
                 sampler.bind(0);
-                ShaderManager::use(kShader::TextureAlpha);
+                pp::panopainter::setup_legacy_canvas_draw_merge_texture_alpha_shader(
-                ShaderManager::u_int(kShaderUniform::Tex, 0);
+                    pp::panopainter::LegacyCanvasDrawMergeTextureAlphaUniforms {
-                ShaderManager::u_float(kShaderUniform::Alpha, canvas->m_canvas->m_layers[layer_index]->m_opacity);
+                        .mvp = plane_mvp_z,
-                ShaderManager::u_int(kShaderUniform::Highlight, canvas->m_canvas->m_layers[layer_index]->m_hightlight);
+                        .texture_slot = 0,
-                ShaderManager::u_mat4(kShaderUniform::MVP, plane_mvp_z);
+                        .alpha = canvas->m_canvas->m_layers[layer_index]->m_opacity,
+                        .highlight = canvas->m_canvas->m_layers[layer_index]->m_hightlight,
+                    });
                 
                 set_active_texture_unit(0);
                 canvas->m_canvas->m_layers[layer_index]->rtt(plane_index).bindTexture();

src/canvas.cpp

@@ -1393,11 +1393,13 @@ void Canvas::draw_merge(bool draw_checkerboard, std::array<bool, 6> faces /*= SI
             else
             {
                 m_cam_fov < 20.f ? m_sampler_nearest.bind(0) : m_sampler.bind(0);
-                ShaderManager::use(kShader::TextureAlpha);
+                pp::panopainter::setup_legacy_canvas_draw_merge_texture_alpha_shader(
-                ShaderManager::u_int(kShaderUniform::Tex, 0);
+                    pp::panopainter::LegacyCanvasDrawMergeTextureAlphaUniforms {
-                ShaderManager::u_float(kShaderUniform::Alpha, m_layers[layer_index]->m_opacity);
+                        .mvp = ortho,
-                ShaderManager::u_int(kShaderUniform::Highlight, m_layers[layer_index]->m_hightlight);
+                        .texture_slot = 0,
-                ShaderManager::u_mat4(kShaderUniform::MVP, ortho);
+                        .alpha = m_layers[layer_index]->m_opacity,
+                        .highlight = m_layers[layer_index]->m_hightlight,
+                    });
 
                 set_active_texture_unit(0);
                 m_layers[layer_index]->rtt(plane_index).bindTexture();
@@ -2216,11 +2218,13 @@ void Canvas::export_depth_thread(std::string file_name)
                 glm::scale(glm::vec3(2));
 
             m_sampler.bind(0);
-            ShaderManager::use(kShader::TextureAlpha);
+            pp::panopainter::setup_legacy_canvas_draw_merge_texture_alpha_shader(
-            ShaderManager::u_int(kShaderUniform::Tex, 0);
+                pp::panopainter::LegacyCanvasDrawMergeTextureAlphaUniforms {
-            ShaderManager::u_float(kShaderUniform::Alpha, 1.f);
+                    .mvp = plane_mvp_z,
-            ShaderManager::u_int(kShaderUniform::Highlight, false);
+                    .texture_slot = 0,
-            ShaderManager::u_mat4(kShaderUniform::MVP, plane_mvp_z);
+                    .alpha = 1.f,
+                    .highlight = false,
+                });
 
             set_active_texture_unit(0);
             m_layers_merge.rtt(plane_index).bindTexture();

src/legacy_canvas_draw_merge_services.h

@@ -16,6 +16,13 @@ struct LegacyCanvasDrawMergeTextureUniforms {
     int texture_slot = 0;
 };
 
+struct LegacyCanvasDrawMergeTextureAlphaUniforms {
+    glm::mat4 mvp { 1.0f };
+    int texture_slot = 0;
+    float alpha = 1.0f;
+    int highlight = 0;
+};
+
 struct LegacyCanvasDrawMergeTextureBlendUniforms {
     glm::mat4 mvp { 1.0f };
     int texture_slot = 0;
@@ -72,6 +79,23 @@ inline void setup_legacy_canvas_draw_merge_texture_shader(
     setup_legacy_canvas_draw_merge_texture_shader(uniforms, legacy_shader_manager_draw_merge_execution());
 }
 
+inline void setup_legacy_canvas_draw_merge_texture_alpha_shader(
+    const LegacyCanvasDrawMergeTextureAlphaUniforms& uniforms,
+    const LegacyCanvasDrawMergeShaderExecution& execution) noexcept
+{
+    execution.use_shader(kShader::TextureAlpha);
+    execution.set_int(kShaderUniform::Tex, uniforms.texture_slot);
+    execution.set_float(kShaderUniform::Alpha, uniforms.alpha);
+    execution.set_int(kShaderUniform::Highlight, uniforms.highlight);
+    execution.set_mat4(kShaderUniform::MVP, uniforms.mvp);
+}
+
+inline void setup_legacy_canvas_draw_merge_texture_alpha_shader(
+    const LegacyCanvasDrawMergeTextureAlphaUniforms& uniforms)
+{
+    setup_legacy_canvas_draw_merge_texture_alpha_shader(uniforms, legacy_shader_manager_draw_merge_execution());
+}
+
 inline void setup_legacy_canvas_draw_merge_texture_blend_shader(
     const LegacyCanvasDrawMergeTextureBlendUniforms& uniforms,
     const LegacyCanvasDrawMergeShaderExecution& execution) noexcept

src/node_canvas.cpp

@@ -392,11 +392,13 @@ void NodeCanvas::draw()
                 glm::translate(glm::vec3(0, 0, -1));
 
             m_sampler.bind(0);
-            ShaderManager::use(kShader::TextureAlpha);
+            pp::panopainter::setup_legacy_canvas_draw_merge_texture_alpha_shader(
-            ShaderManager::u_int(kShaderUniform::Tex, 0);
+                pp::panopainter::LegacyCanvasDrawMergeTextureAlphaUniforms {
-            ShaderManager::u_float(kShaderUniform::Alpha, 1.f);
+                    .mvp = plane_mvp_z,
-            ShaderManager::u_int(kShaderUniform::Highlight, false);
+                    .texture_slot = 0,
-            ShaderManager::u_mat4(kShaderUniform::MVP, plane_mvp_z);
+                    .alpha = 1.f,
+                    .highlight = false,
+                });
 
             set_active_texture_unit(0);
             m_canvas->m_layers_merge.rtt(plane_index).bindTexture();
@@ -583,10 +585,13 @@ void NodeCanvas::draw()
                 else
                 {
                     m_canvas->m_cam_fov < 20.f ? m_sampler_nearest.bind(0) : m_sampler.bind(0);
-                    ShaderManager::use(kShader::TextureAlpha);
+                    pp::panopainter::setup_legacy_canvas_draw_merge_texture_alpha_shader(
-                    ShaderManager::u_int(kShaderUniform::Tex, 0);
+                        pp::panopainter::LegacyCanvasDrawMergeTextureAlphaUniforms {
-                    ShaderManager::u_int(kShaderUniform::Highlight, m_canvas->m_layers[layer_index]->m_hightlight);
+                            .mvp = plane_mvp_z,
-                    ShaderManager::u_mat4(kShaderUniform::MVP, plane_mvp_z);
+                            .texture_slot = 0,
+                            .alpha = 1.f,
+                            .highlight = m_canvas->m_layers[layer_index]->m_hightlight,
+                        });
                 
                     for (int frame = onion_range.first_frame; frame <= onion_range.last_frame; frame++)
                     {