somebar/src/shm_buffer.cpp

// somebar - dwl bar
// See LICENSE file for copyright and license details.

#include <sys/mman.h>
#include <unistd.h>
#include "shm_buffer.hpp"
#include "common.hpp"

constexpr int n = 2;

ShmBuffer::ShmBuffer(int w, int h, wl_shm_format format)
    : width(w)
    , height(h)
    , stride(w*4)
{
    auto oneSize = stride*size_t(h);
    auto totalSize = oneSize * n;
    auto fd = memfd_create("wl_shm", MFD_CLOEXEC);
    ftruncate(fd, totalSize);
    auto pool = wl_shm_create_pool(shm, fd, totalSize);
    auto ptr = reinterpret_cast<uint8_t*>(mmap(nullptr, totalSize, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0));
    _mapping = MemoryMapping {ptr, totalSize};
    close(fd);
    for (auto i=0; i<n; i++) {
        auto offset = oneSize*i;
        _buffers[i] = {
            ptr+offset,
            wl_unique_ptr<wl_buffer> { wl_shm_pool_create_buffer(pool, offset, width, height, stride, format) },
        };
    }
    wl_shm_pool_destroy(pool);
}

uint8_t* ShmBuffer::data() { return _buffers[_current].data; }
wl_buffer* ShmBuffer::buffer() { return _buffers[_current].buffer.get(); }
void ShmBuffer::flip() { _current = 1-_current; }