Function bloom_screenshot_capture

native/linux/src/lib.rs:2791–2837

Capture the Bloom framebuffer as PNG. Called from the geisterhand pump BEFORE end_frame in bloom_end_drawing. The vertices_3d/2d and VP matrix from the game loop are still populated; we render to a fresh surface texture with screenshot capture, producing the same visual output as the real frame.

(out_len: *mut usize)

/// texture with screenshot capture, producing the same visual output as
/// the real frame.
extern "C" fn bloom_screenshot_capture(out_len: *mut usize) -> *mut u8 {
    let eng = engine();

    eng.renderer.screenshot_requested = true;
    eng.scene.prepare(
        &eng.renderer.device,
        &eng.renderer.queue,
        &eng.renderer.vp_matrix(),
        &eng.renderer.prev_vp_matrix,
        eng.renderer.uniform_3d_layout(),
    );
    eng.scene.prepare_materials(&eng.renderer);
    {
        let t = eng.get_time() as f32;
        let dt = eng.delta_time as f32;
        eng.renderer.material_system_begin_frame(t, dt);
    }
    eng.renderer.end_frame_with_scene(&mut eng.scene, &mut eng.profiler);

    match eng.renderer.screenshot_data.take() {
        Some((width, height, rgba)) => {
            match encode_png(width, height, &rgba) {
                Some(png_data) => {
                    let len = png_data.len();
                    let ptr = unsafe { libc::malloc(len) as *mut u8 };
                    if ptr.is_null() {
                        unsafe { *out_len = 0; }
                        return std::ptr::null_mut();
                    }
                    unsafe {
                        std::ptr::copy_nonoverlapping(png_data.as_ptr(), ptr, len);
                        *out_len = len;
                    }
                    ptr
                }
                None => {
                    unsafe { *out_len = 0; }
                    std::ptr::null_mut()
                }
            }
        }
        None => {
            unsafe { *out_len = 0; }
            std::ptr::null_mut()
        }
    }
}

/// Minimal PNG encoder (no external dependency). Matches the macOS
/// implementation byte-for-byte so screenshots are identical across