Logging

stdgba provides a logging system with pluggable backends for emulator debug output. It auto-detects whether the game is running under mGBA or no$gba and routes log messages to the appropriate debug console.

Setup

#include <gba/logger>

using namespace gba::literals;

int main() {
    // Auto-detect emulator and initialise
    if (gba::log::init()) {
        gba::log::info("Game started!");
    }
}

init() returns true if a supported emulator was detected, false otherwise (a null backend is installed so logging calls are safe but do nothing).

Log levels

Five severity levels are available:

gba::log::fatal("Critical error");
gba::log::error("Something failed");
gba::log::warn("Potential problem");
gba::log::info("Status update");
gba::log::debug("Verbose trace");

Filtering by level

gba::log::set_level(gba::log::level::warn);
// Only fatal, error, and warn messages are output

Runtime level selection

Use write() when the log level is determined at runtime:

gba::log::level lvl = config.verbose ? gba::log::level::debug : gba::log::level::info;
gba::log::write(lvl, "Message");

Formatted logging

Log messages support the same format string syntax as <gba/format>:

For full format syntax ({x}, {x:X}, named args, and generator behaviour), see String Formatting.

using namespace gba::literals;

gba::log::info("HP: {hp}"_fmt, "hp"_arg = 42);
gba::log::warn("Sector {s} failed"_fmt, "s"_arg = 3);

Custom backends

Implement the gba::log::backend interface to route logs anywhere:

struct screen_logger : gba::log::backend {
    int line = 0;
    std::size_t write(gba::log::level lvl, const char* msg, std::size_t len) override {
        draw_text(0, line++, msg);
        return len;
    }
};

screen_logger my_logger;
gba::log::set_backend(&my_logger);

Built-in backends

init() tries mGBA first, then no$gba, then falls back to the null backend.