headless_surface.hpp

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#pragma once
 
#include <pulp/render/gpu_surface.hpp>
#include <pulp/render/skia_surface.hpp>
 
#include <cstdint>
#include <functional>
#include <memory>
#include <string>
#include <vector>
 
namespace pulp::canvas { class Canvas; }
 
namespace pulp::render {

class HeadlessSurface {
public:
    struct Config {
        uint32_t width = 800;
        uint32_t height = 600;
        float scale_factor = 1.0f;
        uint8_t clear_r = 0;
        uint8_t clear_g = 0;
        uint8_t clear_b = 0;
        uint8_t clear_a = 255;
        canvas::TextRasterPolicy text_raster_policy = canvas::TextRasterPolicy::legacy;
    };
 
    struct Rgba {
        std::vector<uint8_t> pixels;  
        uint32_t width = 0;
        uint32_t height = 0;
 
        bool empty() const { return pixels.empty() || width == 0 || height == 0; }
        size_t pixel_count() const { return static_cast<size_t>(width) * height; }
    };

    using PaintFn = std::function<void(canvas::Canvas&)>;

    static std::unique_ptr<HeadlessSurface> create(
        const Config& config,
        std::string* last_error_out = nullptr);
 
    virtual ~HeadlessSurface() = default;

    virtual bool is_ready() const = 0;

    virtual Rgba render_rgba(const PaintFn& paint) = 0;

    virtual std::vector<uint8_t> render_png(const PaintFn& paint) = 0;

    virtual std::string last_error() const = 0;

    static std::vector<uint8_t> encode_png(const Rgba& rgba,
                                           std::string* error_out = nullptr);

    static uint64_t rgba_fingerprint(const Rgba& rgba);
};
 
} // namespace pulp::render