libcamera: geometry: SizeRange: Extend with step information

The size range described might be subject to certain step
limitations. Make it possible to record this information.

Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

include/libcamera/geometry.h

@@ -73,18 +73,27 @@ struct SizeRange {
 	}
 
 	SizeRange(unsigned int width, unsigned int height)
-		: min(width, height), max(width, height)
+		: min(width, height), max(width, height), hStep(1), vStep(1)
 	{
 	}
 
 	SizeRange(unsigned int minW, unsigned int minH,
 		  unsigned int maxW, unsigned int maxH)
-		: min(minW, minH), max(maxW, maxH)
+		: min(minW, minH), max(maxW, maxH), hStep(1), vStep(1)
+	{
+	}
+
+	SizeRange(unsigned int minW, unsigned int minH,
+		  unsigned int maxW, unsigned int maxH,
+		  unsigned int hstep, unsigned int vstep)
+		: min(minW, minH), max(maxW, maxH), hStep(hstep), vStep(vstep)
 	{
 	}
 
 	Size min;
 	Size max;
+	unsigned int hStep;
+	unsigned int vStep;
 };
 
 bool operator==(const SizeRange &lhs, const SizeRange &rhs);

src/libcamera/geometry.cpp

@@ -186,9 +186,29 @@ bool operator<(const Size &lhs, const Size &rhs)
  * \struct SizeRange
  * \brief Describe a range of sizes
  *
- * SizeRange describes a range of sizes included in the [min, max]
+ * A SizeRange describes a range of sizes included in the [min, max] interval
- * interval for both the width and the height. If the minimum and
+ * for both the width and the height. If the minimum and maximum sizes are
- * maximum sizes are identical it represents a single size.
+ * identical it represents a single size.
+ *
+ * Size ranges may further limit the valid sizes through steps in the horizontal
+ * and vertical direction. The step values represent the increase in pixels
+ * between two valid width or height values, starting from the minimum. Valid
+ * sizes within the range are thus expressed as
+ *
+ *	width = min.width + hStep * x
+ *	height = min.height + vStep * y
+ *
+ *	Where
+ *
+ *	width <= max.width
+ *	height < max.height
+ *
+ * Note that the step values are not equivalent to alignments, as the minimum
+ * width or height may not be a multiple of the corresponding step.
+ *
+ * The step values may be zero when the range describes only minimum and
+ * maximum sizes without implying that all, or any, intermediate size is valid.
+ * SizeRange instances the describe a single size have both set values set to 1.
  */
 
 /**
@@ -213,6 +233,19 @@ bool operator<(const Size &lhs, const Size &rhs)
  * \param[in] maxH The maximum height
  */
 
+/**
+ * \fn SizeRange::SizeRange(unsigned int minW, unsigned int minH,
+ *			    unsigned int maxW, unsigned int maxH,
+ *			    unsigned int hstep, unsigned int vstep)
+ * \brief Construct an initialized size range
+ * \param[in] minW The minimum width
+ * \param[in] minH The minimum height
+ * \param[in] maxW The maximum width
+ * \param[in] maxH The maximum height
+ * \param[in] hstep The horizontal step
+ * \param[in] vstep The vertical step
+ */
+
 /**
  * \var SizeRange::min
  * \brief The minimum size
@@ -223,6 +256,16 @@ bool operator<(const Size &lhs, const Size &rhs)
  * \brief The maximum size
  */
 
+/**
+ * \var SizeRange::hStep
+ * \brief The horizontal step
+ */
+
+/**
+ * \var SizeRange::vStep
+ * \brief The vertical step
+ */
+
 /**
  * \brief Compare size ranges for equality
  * \return True if the two size ranges are equal, false otherwise