notcurses/include/ncpp/Plot.hh
Marek Habersack a29bfe9c42 [C++] Deal with widgets grabbing full ownership of Panel
Fixes: https://github.com/dankamongmen/notcurses/issues/1009

Whenever a widget is created with its `*_create` function it currently
claims full ownership of the passed panel, including its destruction.
However, the C++ wrapper around the panel is not aware of this and will
attempt to destroy the native panel in the destructor, leading to
segfaults.

Fix this by introduction of a `Widget` class which contains the logic to
properly modify the `Panel` instance to not double-destroy the native
panel.  The solution is a bit fragile since the `Panel` instance is left
intact (we can't free it for the user) in a state that's safe for the
C++ wrapper, but calling any C function via the wrapper **will** pass a
`NULL` pointer in the panel argument - therefore the C functions MUST be
proofed against this.  The proofing belongs in the C backend code since
this protects also C and other language binding users from such abuse.

The Widget class will first verify that the passed `Plane` instance
hasn't already been "disowned" and will throw an exception to the effect
if it was.  Next, it will proceed to take over ownership of the native
panel instance and mark the passed `Panel` as "invalid" (i.e. not owning
any native panel instance anymore)

The above changes require modification of `Panel` instances and so all
the widget constructors taking `const*` or `const&` have been removed
from widget classes.
2020-10-03 13:19:49 -04:00

164 lines
4.1 KiB
C++

#ifndef __NCPP_PLOT_HH
#define __NCPP_PLOT_HH
#include <type_traits>
#include <notcurses/notcurses.h>
#include "NCAlign.hh"
#include "Plane.hh"
#include "Utilities.hh"
#include "Widget.hh"
namespace ncpp
{
template<typename TPlot, typename TCoord>
class NCPP_API_EXPORT PlotBase : public Widget
{
static constexpr bool is_double = std::is_same_v<TCoord,double>;
static constexpr bool is_uint64 = std::is_same_v<TCoord,uint64_t>;
public:
bool add_sample (uint64_t x, TCoord y) const NOEXCEPT_MAYBE
{
int ret;
if constexpr (is_double) {
ret = ncdplot_add_sample (plot, x, y);
} else {
ret = nduplot_add_sample (plot, x, y);
}
return error_guard (ret, -1);
}
bool set_sample (uint64_t x, TCoord y) const NOEXCEPT_MAYBE
{
int ret;
if constexpr (is_double) {
ret = ncdplot_set_sample (plot, x, y);
} else {
ret = nduplot_set_sample (plot, x, y);
}
return error_guard (ret, -1);
}
bool sample (uint64_t x, TCoord* y) const NOEXCEPT_MAYBE
{
int ret;
if constexpr (is_double) {
ret = ncdplot_sample (plot, x, y);
} else {
ret = ncuplot_sample (plot, x, y);
}
return error_guard (ret, -1);
}
protected:
explicit PlotBase (Plane *plane, const ncplot_options *opts, TCoord miny = 0, TCoord maxy = 0)
: Widget (Utilities::get_notcurses_cpp (plane))
{
static_assert (is_double || is_uint64, "PlotBase must be parameterized with either 'double' or 'uint64_t' types");
if constexpr (is_double) {
static_assert (std::is_same_v<TPlot, ncdplot>, "ncdplot must be used for a plot using double coordinates");
} else {
static_assert (std::is_same_v<TPlot, ncuplot>, "ncuplot must be used for a plot using uint64_t coordinates");
}
ensure_valid_plane (plane);
if (!plane->is_valid ())
throw invalid_argument ("Invalid Plane object passed in 'plane'. Widgets must not reuse the same plane.");
if (opts == nullptr)
throw invalid_argument ("'opts' must be a valid pointer");
if constexpr (is_uint64) {
plot = ncuplot_create (Utilities::to_ncplane (plane), opts, miny, maxy);
} else {
plot = ncdplot_create (Utilities::to_ncplane (plane), opts, miny, maxy);
}
if (plot == nullptr)
throw init_error ("Notcurses failed to create a new plot");
take_plane_ownership (plane);
}
~PlotBase ()
{
if (!is_notcurses_stopped ()) {
if constexpr (is_double) {
ncdplot_destroy (plot);
} else {
ncuplot_destroy (plot);
}
}
}
TPlot *get_plot () const noexcept
{
return plot;
}
private:
TPlot *plot;
};
class NCPP_API_EXPORT PlotU : public PlotBase<ncuplot, uint64_t>
{
public:
static ncplot_options default_options;
public:
explicit PlotU (Plane *plane, const ncplot_options *opts = nullptr)
: PlotU (static_cast<const Plane*>(plane), opts)
{}
explicit PlotU (Plane const* plane, const ncplot_options *opts = nullptr)
: PlotBase (const_cast<Plane*>(plane), opts == nullptr ? &default_options : opts)
{}
explicit PlotU (Plane &plane, const ncplot_options *opts = nullptr)
: PlotU (static_cast<Plane const&>(plane), opts)
{}
explicit PlotU (Plane const& plane, const ncplot_options *opts = nullptr)
: PlotBase (const_cast<Plane*>(&plane), opts == nullptr ? &default_options : opts)
{}
Plane* get_plane () const noexcept;
};
class NCPP_API_EXPORT PlotD : public PlotBase<ncdplot, double>
{
public:
static ncplot_options default_options;
public:
explicit PlotD (Plane *plane, const ncplot_options *opts = nullptr)
: PlotD (static_cast<const Plane*>(plane), opts)
{}
explicit PlotD (Plane const* plane, const ncplot_options *opts = nullptr)
: PlotBase (const_cast<Plane*>(plane), opts == nullptr ? &default_options : opts)
{}
explicit PlotD (Plane &plane, const ncplot_options *opts = nullptr)
: PlotD (static_cast<Plane const&>(plane), opts)
{}
explicit PlotD (Plane const& plane, const ncplot_options *opts = nullptr)
: PlotBase (const_cast<Plane*>(&plane), opts == nullptr ? &default_options : opts)
{}
Plane* get_plane () const noexcept;
};
using Plot = PlotU;
}
#endif