Route NodeCanvas erase setup through helper

src/legacy_canvas_stroke_erase_services.h

@@ -0,0 +1,49 @@
+#pragma once
+
+#include "shader.h"
+
+#include <functional>
+
+namespace pp::panopainter {
+
+struct LegacyStrokeEraseUniforms {
+    glm::mat4 mvp { 1.0f };
+    int texture_slot = 0;
+    int stroke_texture_slot = 1;
+    int mask_texture_slot = 2;
+    bool mask_enabled = false;
+};
+
+struct LegacyStrokeEraseShaderExecution {
+    std::function<void(kShader)> use_shader;
+    std::function<void(kShaderUniform, int)> set_int;
+    std::function<void(kShaderUniform, const glm::mat4&)> set_mat4;
+};
+
+[[nodiscard]] inline LegacyStrokeEraseShaderExecution legacy_shader_manager_stroke_erase_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_stroke_erase_shader(
+    const LegacyStrokeEraseUniforms& uniforms,
+    const LegacyStrokeEraseShaderExecution& execution) noexcept
+{
+    execution.use_shader(kShader::CompErase);
+    execution.set_int(kShaderUniform::Tex, uniforms.texture_slot);
+    execution.set_int(kShaderUniform::TexStroke, uniforms.stroke_texture_slot);
+    execution.set_int(kShaderUniform::TexMask, uniforms.mask_texture_slot);
+    execution.set_int(kShaderUniform::Mask, uniforms.mask_enabled);
+    execution.set_mat4(kShaderUniform::MVP, uniforms.mvp);
+}
+
+inline void setup_legacy_stroke_erase_shader(const LegacyStrokeEraseUniforms& uniforms)
+{
+    setup_legacy_stroke_erase_shader(uniforms, legacy_shader_manager_stroke_erase_execution());
+}
+
+} // namespace pp::panopainter