libcamera: Rename "shutter speed" to "exposure time"

The terms "shutter" and "shutter speed" are used through libcamera to
mean "exposure time". This is confusing, both due to "speed" being used
as "time" while it should be the inverse (i.e. a maximum speed should
correspond to the minimum time), and due to "shutter speed" and
"exposure time" being used in different places with the same meaning.

To improve clarity of the code base and the documentation, use "exposure
time" consistently to replace "shutter speed".

This rename highlighted another vocabulary issue in libcamera. The
ExposureModeHelper::splitExposure() function used to document that it
splits "exposure time into shutter time and gain". It has been reworded
to "split exposure into exposure time and gain". That is not entirely
satisfactory, as "exposure" has a defined meaning in photography (see
https://en.wikipedia.org/wiki/Exposure_(photography)) that is not
expressed as a duration. This issue if left to be addressed separately.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Naushir Patuck <naush@raspberrypi.com>
Acked-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

1 files changed, 7 insertions, 7 deletions

diff --git a/src/ipa/libipa/exposure_mode_helper.h b/src/ipa/libipa/exposure_mode_helper.h
index 85c665d7..c5be1b67 100644
--- a/src/ipa/libipa/exposure_mode_helper.h
+++ b/src/ipa/libipa/exposure_mode_helper.h
@@ -24,26 +24,26 @@ public:
 	ExposureModeHelper(const Span<std::pair<utils::Duration, double>> stages);
 	~ExposureModeHelper() = default;
 
-	void setLimits(utils::Duration minShutter, utils::Duration maxShutter,
+	void setLimits(utils::Duration minExposureTime, utils::Duration maxExposureTime,
 		       double minGain, double maxGain);
 
 	std::tuple<utils::Duration, double, double>
 	splitExposure(utils::Duration exposure) const;
 
-	utils::Duration minShutter() const { return minShutter_; }
-	utils::Duration maxShutter() const { return maxShutter_; }
+	utils::Duration minExposureTime() const { return minExposureTime_; }
+	utils::Duration maxExposureTime() const { return maxExposureTime_; }
 	double minGain() const { return minGain_; }
 	double maxGain() const { return maxGain_; }
 
 private:
-	utils::Duration clampShutter(utils::Duration shutter) const;
+	utils::Duration clampExposureTime(utils::Duration exposureTime) const;
 	double clampGain(double gain) const;
 
-	std::vector<utils::Duration> shutters_;
+	std::vector<utils::Duration> exposureTimes_;
 	std::vector<double> gains_;
 
-	utils::Duration minShutter_;
-	utils::Duration maxShutter_;
+	utils::Duration minExposureTime_;
+	utils::Duration maxExposureTime_;
 	double minGain_;
 	double maxGain_;
 };