From 1c4d4801850559d6f919eef5c2ffbaf7675dbc46 Mon Sep 17 00:00:00 2001
From: Christian Rauch <Rauch.Christian@gmx.de>
Date: Tue, 5 Jul 2022 10:55:48 +0100
Subject: libcamera: controls: Use std::optional to handle invalid control
 values

Previously, ControlList::get<T>() would use default constructed objects to
indicate that a ControlList does not have the requested Control. This has
several disadvantages: 1) It requires types to be default constructible,
2) it does not differentiate between a default constructed object and an
object that happens to have the same state as a default constructed object.

std::optional<T> additionally stores the information if the object is valid
or not, and therefore is more expressive than a default constructed object.

Signed-off-by: Christian Rauch <Rauch.Christian@gmx.de>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
---
 include/libcamera/controls.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

(limited to 'include')

diff --git a/include/libcamera/controls.h b/include/libcamera/controls.h
index 665bcac1..192be784 100644
--- a/include/libcamera/controls.h
+++ b/include/libcamera/controls.h
@@ -8,6 +8,7 @@
 #pragma once
 
 #include <assert.h>
+#include <optional>
 #include <set>
 #include <stdint.h>
 #include <string>
@@ -373,11 +374,11 @@ public:
 	bool contains(unsigned int id) const;
 
 	template<typename T>
-	T get(const Control<T> &ctrl) const
+	std::optional<T> get(const Control<T> &ctrl) const
 	{
 		const ControlValue *val = find(ctrl.id());
 		if (!val)
-			return T{};
+			return std::nullopt;
 
 		return val->get<T>();
 	}
-- 
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