_rsvg_push_view_box (RsvgDrawingCtx * ctx, double w, double h)
{
    RsvgViewBox *vb = g_new (RsvgViewBox, 1);
    *vb = ctx->vb;
    ctx->vb_stack = g_slist_prepend (ctx->vb_stack, vb);
    ctx->vb.w = w;
    ctx->vb.h = h;
}
_rsvg_push_view_box (RsvgDrawingCtx * ctx, double w, double h)
{
    RsvgViewBox *vb = g_new (RsvgViewBox, 1);
    *vb = ctx->vb;
    ctx->vb_stack = g_slist_prepend (ctx->vb_stack, vb);
    ctx->vb.w = w;
    ctx->vb.h = h;
}