Isolate draw merge background shader setup

src/canvas.cpp

@@ -2,6 +2,7 @@
 #include "log.h"
 #include "canvas.h"
 #include "app.h"
+#include "legacy_canvas_draw_merge_services.h"
 #include "legacy_gl_renderbuffer_dispatch.h"
 #include "legacy_canvas_stroke_commit_services.h"
 #include "legacy_canvas_stroke_composite_services.h"
@@ -1273,9 +1274,11 @@ void Canvas::draw_merge(bool draw_checkerboard, std::array<bool, 6> faces /*= SI
         {
             if (draw_checkerboard)
             {
-                ShaderManager::use(kShader::Checkerboard);
-                ShaderManager::u_int(kShaderUniform::Colorize, false);
-                ShaderManager::u_mat4(kShaderUniform::MVP, ortho);
+                pp::panopainter::setup_legacy_canvas_draw_merge_checkerboard_shader(
+                    pp::panopainter::LegacyCanvasDrawMergeCheckerboardUniforms {
+                        .mvp = ortho,
+                        .colorize = false,
+                    });
                 m_plane.draw_fill();
             }
             apply_canvas_capability(blend_state(), true);
@@ -1454,9 +1457,11 @@ void Canvas::draw_merge(bool draw_checkerboard, std::array<bool, 6> faces /*= SI
             //draw the grid
             if (draw_checkerboard)
             {
-                ShaderManager::use(kShader::Checkerboard);
-                ShaderManager::u_int(kShaderUniform::Colorize, false);
-                ShaderManager::u_mat4(kShaderUniform::MVP, ortho);
+                pp::panopainter::setup_legacy_canvas_draw_merge_checkerboard_shader(
+                    pp::panopainter::LegacyCanvasDrawMergeCheckerboardUniforms {
+                        .mvp = ortho,
+                        .colorize = false,
+                    });
                 m_plane.draw_fill();
             }
 
@@ -1464,9 +1469,11 @@ void Canvas::draw_merge(bool draw_checkerboard, std::array<bool, 6> faces /*= SI
             m_sampler.bind(0);
             set_active_texture_unit(0);
             m_merge_tex.bind();
-            ShaderManager::use(kShader::Texture);
-            ShaderManager::u_int(kShaderUniform::Tex, 0);
-            ShaderManager::u_mat4(kShaderUniform::MVP, ortho);
+            pp::panopainter::setup_legacy_canvas_draw_merge_texture_shader(
+                pp::panopainter::LegacyCanvasDrawMergeTextureUniforms {
+                    .mvp = ortho,
+                    .texture_slot = 0,
+                });
             m_plane.draw_fill();
             m_merge_tex.unbind();
         }

src/legacy_canvas_draw_merge_services.h

@@ -0,0 +1,64 @@
+#pragma once
+
+#include "shader.h"
+
+#include <functional>
+
+namespace pp::panopainter {
+
+struct LegacyCanvasDrawMergeCheckerboardUniforms {
+    glm::mat4 mvp { 1.0f };
+    bool colorize = false;
+};
+
+struct LegacyCanvasDrawMergeTextureUniforms {
+    glm::mat4 mvp { 1.0f };
+    int texture_slot = 0;
+};
+
+struct LegacyCanvasDrawMergeShaderExecution {
+    std::function<void(kShader)> use_shader;
+    std::function<void(kShaderUniform, int)> set_int;
+    std::function<void(kShaderUniform, const glm::mat4&)> set_mat4;
+};
+
+[[nodiscard]] inline LegacyCanvasDrawMergeShaderExecution legacy_shader_manager_draw_merge_execution() noexcept
+{
+    return {
+        .use_shader = [](kShader shader) { ShaderManager::use(shader); },
+        .set_int = [](kShaderUniform uniform, int value) { ShaderManager::u_int(uniform, value); },
+        .set_mat4 = [](kShaderUniform uniform, const glm::mat4& value) { ShaderManager::u_mat4(uniform, value); },
+    };
+}
+
+inline void setup_legacy_canvas_draw_merge_checkerboard_shader(
+    const LegacyCanvasDrawMergeCheckerboardUniforms& uniforms,
+    const LegacyCanvasDrawMergeShaderExecution& execution) noexcept
+{
+    execution.use_shader(kShader::Checkerboard);
+    execution.set_int(kShaderUniform::Colorize, uniforms.colorize);
+    execution.set_mat4(kShaderUniform::MVP, uniforms.mvp);
+}
+
+inline void setup_legacy_canvas_draw_merge_checkerboard_shader(
+    const LegacyCanvasDrawMergeCheckerboardUniforms& uniforms)
+{
+    setup_legacy_canvas_draw_merge_checkerboard_shader(uniforms, legacy_shader_manager_draw_merge_execution());
+}
+
+inline void setup_legacy_canvas_draw_merge_texture_shader(
+    const LegacyCanvasDrawMergeTextureUniforms& uniforms,
+    const LegacyCanvasDrawMergeShaderExecution& execution) noexcept
+{
+    execution.use_shader(kShader::Texture);
+    execution.set_int(kShaderUniform::Tex, uniforms.texture_slot);
+    execution.set_mat4(kShaderUniform::MVP, uniforms.mvp);
+}
+
+inline void setup_legacy_canvas_draw_merge_texture_shader(
+    const LegacyCanvasDrawMergeTextureUniforms& uniforms)
+{
+    setup_legacy_canvas_draw_merge_texture_shader(uniforms, legacy_shader_manager_draw_merge_execution());
+}
+
+} // namespace pp::panopainter