[PATCH v1] gstreamer: Use `Control<>` objects when setting controls

[Kieran Bingham]

Quoting Laurent Pinchart (2025-03-28 17:33:49)
> Hi Barnabás,
> 
> Thank you for the patch.
> 
> On Fri, Mar 28, 2025 at 05:07:36PM +0100, Barnabás Pőcze wrote:
> > `g_value_get_boolean()` returns `gboolean`, which is actually `int`. Thus
> > 
> >   // ControlValue x;
> >   auto val = g_value_get_boolean(...);
> >   x.set(val);
> > 
> > will cause `ControlValue::set<int, ...>(const int&)` to be called, which
> > will save the value as `ControlTypeInteger32`, not `ControlTypeBoolean`.
> 
> Oops... good catch !
> 
> > Then, if something tries to retrieve the boolean value, it will run into an
> > assertion failure:
> > 
> >   Assertion `type_ == details::control_type<std::remove_cv_t<T>>::value' failed.
> > 
> > in `ControlValue::set()`.
> > 
> > Fix this by using the appropriately typed `Control<>` object when setting
> > the value in the `ControlList` as this ensures that the value will be
> > converted to the actual type of the control.
> > 
> > Bug: https://bugs.libcamera.org/show_bug.cgi?id=261
> > Signed-off-by: Barnabás Pőcze <barnabas.pocze at ideasonboard.com>
> > ---
> > There is a simpler fix to this issue as well:
> > 
> >       diff --git a/src/gstreamer/gstlibcamera-controls.cpp.in b/src/gstreamer/gstlibcamera-controls.cpp.in
> >       index d937b19e6..8378b5fd0 100644
> >       --- a/src/gstreamer/gstlibcamera-controls.cpp.in
> >       +++ b/src/gstreamer/gstlibcamera-controls.cpp.in
> >       @@ -271,7 +271,7 @@ bool GstCameraControls::setProperty(guint propId, const GValue *value,
> >                       }
> >                       Rectangle val = value_get_rectangle(value);
> >       {%- else %}
> >       -               auto val = g_value_get_{{ ctrl.gtype }}(value);
> >       +               {{ ctrl.element_type }} val = g_value_get_{{ ctrl.gtype }}(value);
> 
> I knew auto was bad :-D
> 
> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

Is this reviewing the simple fix, or the fix below?

If there's a simpler fix - what's the rationale for the longer fix
below?


I don't mind which one is merged, they both have lots of templating
magic which makes this hard to review, but fixing the bug is nice ;-)

For which ever of these approaches is desired/appropriate:

Acked-by: Kieran Bingham <kieran.bingham at ideasonboard.com>

--
Kieran

> 
> You fixed the bug even before I had a chance to look at the bug report.
> Kudos !
> 
> >       {%- endif %}
> >                       control.set(val);
> >       {%- endif %}
> > 
> > ---
> >  src/gstreamer/gstlibcamera-controls.cpp.in | 13 ++++---------
> >  1 file changed, 4 insertions(+), 9 deletions(-)
> > 
> > diff --git a/src/gstreamer/gstlibcamera-controls.cpp.in b/src/gstreamer/gstlibcamera-controls.cpp.in
> > index d937b19e6..89c530da0 100644
> > --- a/src/gstreamer/gstlibcamera-controls.cpp.in
> > +++ b/src/gstreamer/gstlibcamera-controls.cpp.in
> > @@ -223,7 +223,6 @@ bool GstCameraControls::setProperty(guint propId, const GValue *value,
> >  {%- for ctrl in ctrls %}
> > 
> >       case controls::{{ ctrl.namespace }}{{ ctrl.name|snake_case|upper }}: {
> > -             ControlValue control;
> >  {%- if ctrl.is_array %}
> >               size_t size = gst_value_array_get_size(value);
> >  {%- if ctrl.size != 0 %}
> > @@ -254,12 +253,9 @@ bool GstCameraControls::setProperty(guint propId, const GValue *value,
> >               }
> > 
> >  {%- if ctrl.size == 0 %}
> > -             control.set(Span<const {{ ctrl.element_type }}>(values.data(),
> > -                                                             size));
> > +             Span<const {{ ctrl.element_type }}> val(values.data(), size);
> >  {%- else %}
> > -             control.set(Span<const {{ ctrl.element_type }},
> > -                              {{ ctrl.size }}>(values.data(),
> > -                                               {{ ctrl.size }}));
> > +             Span<const {{ ctrl.element_type }}, {{ ctrl.size }}> val(values.data(), size);
> >  {%- endif %}
> >  {%- else %}
> >  {%- if ctrl.is_rectangle %}
> > @@ -273,10 +269,9 @@ bool GstCameraControls::setProperty(guint propId, const GValue *value,
> >  {%- else %}
> >               auto val = g_value_get_{{ ctrl.gtype }}(value);
> >  {%- endif %}
> > -             control.set(val);
> >  {%- endif %}
> > -             controls_.set(propId, control);
> > -             controls_acc_.set(propId, control);
> > +             controls_.set(controls::{{ ctrl.namespace }}{{ ctrl.name }}, val);
> > +             controls_acc_.set(controls::{{ ctrl.namespace }}{{ ctrl.name }}, val);
> >               return true;
> >       }
> >  {%- endfor %}
> 
> -- 
> Regards,
> 
> Laurent Pinchart