[libcamera-devel] [PATCH v2] libcamera: geometry: Add isNull() function to Size class

[Laurent Pinchart]

Hi Jacopo,

On Thu, Jun 25, 2020 at 11:26:17AM +0200, Jacopo Mondi wrote:
> On Thu, Jun 25, 2020 at 12:07:39PM +0300, Laurent Pinchart wrote:
> > On Thu, Jun 25, 2020 at 11:07:33AM +0200, Jacopo Mondi wrote:
> >> On Thu, Jun 25, 2020 at 11:57:05AM +0300, Laurent Pinchart wrote:
> >>> On Thu, Jun 25, 2020 at 09:37:39AM +0200, Jacopo Mondi wrote:
> >>>> On Thu, Jun 25, 2020 at 04:23:30AM +0300, Laurent Pinchart wrote:
> >>>>> It's common for code to check if a size is null. Add a helper function
> >>>>> to do so.
> >>>>>
> >>>>> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> >>>>> ---
> >>>>> Changes since v1:
> >>>>>
> >>>>> - Add test
> >>>>> ---
> >>>>>  include/libcamera/geometry.h |  1 +
> >>>>>  src/libcamera/geometry.cpp   |  6 ++++++
> >>>>>  test/geometry.cpp            | 10 ++++++++++
> >>>>>  3 files changed, 17 insertions(+)
> >>>>>
> >>>>> diff --git a/include/libcamera/geometry.h b/include/libcamera/geometry.h
> >>>>> index edda42cf34cc..7d4b8bcfe3d8 100644
> >>>>> --- a/include/libcamera/geometry.h
> >>>>> +++ b/include/libcamera/geometry.h
> >>>>> @@ -41,6 +41,7 @@ struct Size {
> >>>>>  	unsigned int width;
> >>>>>  	unsigned int height;
> >>>>>
> >>>>> +	bool isNull() const { return !width && !height; }
> >>>>
> >>>> Is isNull() a good name ? We have isValid() for PixelFormat() should
> >>>> we stay consistent ?
> >>>
> >>> I initially had isEmpty(), and I've taken inspiration from QRect the
> >>> defines isNull() as !width && !height (or rather width <= 0 && height <=
> >>> 0, but our width and height are unsigned), and isEmpty() as !width ||
> >>> !height.
> >>
> >> I was more concerned about the fact we have a number of classes using
> >> isValid() already, and consistency with the library is important,
> >> otherwise it's a constant "go to look at the class definition", much
> >> similar to when we had Rectangle::width and Size::w
> >>
> >> include/libcamera/file_descriptor.h:    bool isValid() const { return fd_ != nullptr; }
> >> include/libcamera/internal/formats.h:   bool isValid() const { return format.isValid(); }
> >> include/libcamera/internal/ipa_module.h:        bool isValid() const;
> >> include/libcamera/internal/ipa_proxy.h: bool isValid() const { return valid_; }
> >> include/libcamera/internal/pub_key.h:   bool isValid() const { return valid_; }
> >> include/libcamera/internal/v4l2_pixelformat.h:  bool isValid() const { return fourcc_ != 0; }
> >> include/libcamera/pixel_format.h:       constexpr bool isValid() const { return fourcc_ != 0; }
> >>
> >> For the record we have one isEmpty()
> >> nclude/libcamera/internal/formats.h:   bool isEmpty() const;
> >>
> >> but no isNull(). I would avoid introducing another term for a similar,
> >> if not the same, concept.
> >
> > That boils down to the question of is a Size(0, 0) "invalid" ?
> 
> Sorry about this, but how would you define a "valid" size ? To me
> whatever size that has -both- width and height > 0 is valid.
> Everything else is not. I don't really see a need for a distinction
> between a "valid" (w || h) and a "!null" (or zero) one (w && h).
> 
> A size with any of its members set to 0 is not valid. Is this too
> harsh ?

That wasn't the question :-) My point is that the name "valid" doesn't
seem to be a good candidate to me here, I wouldn't call a size that has
a width or height (or both) equal to 0 as "invalid". It's a
zero/null/empty size, but not intrinsicly invalid. Whether such a size
can be valid for a given usage depends on the usage, but isn't a
property of the Size class in my opinion.

> >>>> Otherwise
> >>>> Reviewed-by: Jacopo Mondi <jacopo at jmondi.org>
> >>>>
> >>>>>  	const std::string toString() const;
> >>>>>  };
> >>>>>
> >>>>> diff --git a/src/libcamera/geometry.cpp b/src/libcamera/geometry.cpp
> >>>>> index fd78cf2c0ab7..24c44fb43acf 100644
> >>>>> --- a/src/libcamera/geometry.cpp
> >>>>> +++ b/src/libcamera/geometry.cpp
> >>>>> @@ -107,6 +107,12 @@ bool operator==(const Rectangle &lhs, const Rectangle &rhs)
> >>>>>   * \brief The Size height
> >>>>>   */
> >>>>>
> >>>>> +/**
> >>>>> + * \fn bool Size::isNull() const
> >>>>> + * \brief Check if the size is null
> >>>>> + * \return True if both the width and height are 0, or false otherwise
> >>>>> + */
> >>>>> +
> >>>>>  /**
> >>>>>   * \brief Assemble and return a string describing the size
> >>>>>   * \return A string describing the size
> >>>>> diff --git a/test/geometry.cpp b/test/geometry.cpp
> >>>>> index 27e65565d7c6..904ad92c9448 100644
> >>>>> --- a/test/geometry.cpp
> >>>>> +++ b/test/geometry.cpp
> >>>>> @@ -36,6 +36,16 @@ protected:
> >>>>>
> >>>>>  	int run()
> >>>>>  	{
> >>>>> +		if (!Size().isNull() || !Size(0, 0).isNull()) {
> >>>>> +			cout << "Null size incorrectly reported as not null" << endl;
> >>>>> +			return TestFail;
> >>>>> +		}
> >>>>> +
> >>>>> +		if (Size(0, 100).isNull() || Size(100, 0).isNull() || Size(100, 100).isNull()) {
> >>>>> +			cout << "Non-null size incorrectly reported as null" << endl;
> >>>>> +			return TestFail;
> >>>>> +		}
> >>>>> +
> >>>>>  		/* Test Size equality and inequality. */
> >>>>>  		if (!compare(Size(100, 100), Size(100, 100), &operator==, "==", true))
> >>>>>  			return TestFail;

-- 
Regards,

Laurent Pinchart