libcamera: geometry: Add isNull() function to Size class

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@ideasonboard.com>
Reviewed-by: Umang Jain <email@uajain.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

include/libcamera/geometry.h

@@ -41,6 +41,7 @@ struct Size {
 	unsigned int width;
 	unsigned int height;
 
+	bool isNull() const { return !width && !height; }
 	const std::string toString() const;
 };
 

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

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;