shared: add ColorItem from Gravity screensaver.

* A useful utility class that will also be used by Terminal later

Change-Id: I23020a401fbab7d4116df31f965ae61ecaf2a6cd

headers/private/shared/ColorItem.h

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016 Haiku, Inc. All rights reserved.
+ * Copyright 2016-2022 Haiku, Inc. All rights reserved.
  * Distributed under the terms of the MIT License.
  *
  * Authors:
@@ -20,7 +20,8 @@ public:
 							ColorItem(const char* string, rgb_color color);
 
 	virtual	void			DrawItem(BView* owner, BRect frame, bool complete);
-	virtual	void			SetColor(rgb_color color);
+			void			SetColor(rgb_color color) { fColor = color; }
+			rgb_color		Color() const { return fColor; }
 
 private:
 			rgb_color		fColor;

src/add-ons/screen_savers/gravity/Jamfile

@@ -1,6 +1,7 @@
 SubDir HAIKU_TOP src add-ons screen_savers gravity ;
 UseBuildFeatureHeaders glu ;
 UseBuildFeatureHeaders mesa ;
+UsePrivateHeaders shared ;
 
 # For GCC2
 if $(TARGET_CC_IS_LEGACY_GCC_$(TARGET_PACKAGING_ARCH)) = 1 {
@@ -10,7 +11,6 @@ if $(TARGET_CC_IS_LEGACY_GCC_$(TARGET_PACKAGING_ARCH)) = 1 {
 AddResources Gravity : Gravity.rdef ;
 
 local sources =
-	ColorItem.cpp
 	ConfigView.cpp
 	Gravity.cpp
 	GravitySource.cpp
@@ -30,7 +30,7 @@ Includes [ FGristFiles $(sources) ] :
 ScreenSaver Gravity :
 	$(sources)
 	:
-	be screensaver localestub [ TargetLibstdc++ ]
+	be screensaver shared localestub [ TargetLibstdc++ ]
 	[ BuildFeatureAttribute glu : library ]
 	[ BuildFeatureAttribute mesa : library ]
 ;

src/kits/shared/ColorItem.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016 Haiku, Inc. All rights reserved.
+ * Copyright 2016-2022 Haiku, Inc. All rights reserved.
  * Distributed under the terms of the MIT License.
  *
  * Authors:
@@ -87,10 +87,3 @@ ColorItem::DrawItem(BView* owner, BRect frame, bool complete)
 	owner->SetHighColor(highColor);
 	owner->SetLowColor(lowColor);
 }
-
-
-void
-ColorItem::SetColor(rgb_color color)
-{
-	fColor = color;
-}

src/kits/shared/Jamfile

@@ -30,6 +30,7 @@ for architectureObject in [ MultiArchSubDirSetup ] {
 			AttributeUtilities.cpp
 			BitmapButton.cpp
 			CalendarView.cpp
+			ColorItem.cpp
 			ColorQuantizer.cpp
 			CommandPipe.cpp
 			DateTimeEdit.cpp