BCheckBox: Add tri-state support

* Add possible control state B_CONTROL_PARTIALLY_ON and support it in
  BCheckBox and BControlLook.
* BCheckBox: Add partialStateToOff property defining whether the
  partial state should transition to off. Defaults to false (i.e.
  partial to on).

headers/os/interface/CheckBox.h

@@ -69,6 +69,9 @@ public:
 
 	virtual	status_t			Perform(perform_code code, void* data);
 
+			bool				IsPartialStateToOff() const;
+			void				SetPartialStateToOff(bool partialToOff);
+
 protected:
 	virtual	void				LayoutInvalidated(bool descendants = false);
 
@@ -81,6 +84,7 @@ private:
 private:
 			BRect				_CheckBoxFrame() const;
 			BSize				_ValidatePreferredSize();
+			int32				_NextState() const;
 
 private:
 	// Forbidden
@@ -89,6 +93,7 @@ private:
 private:
 			BSize				fPreferredSize;
 			bool				fOutlined;
+			bool				fPartialToOff;
 };
 
 #endif // _CHECK_BOX_H

headers/os/interface/Control.h

@@ -12,7 +12,8 @@
 
 enum {
 	B_CONTROL_OFF = 0,
-	B_CONTROL_ON = 1
+	B_CONTROL_ON = 1,
+	B_CONTROL_PARTIALLY_ON = 2
 };
 
 class BWindow;

headers/os/interface/ControlLook.h

@@ -69,13 +69,14 @@ public:
 	};
 
 	enum {
-		B_FOCUSED			= 1 << 0,
-		B_CLICKED			= 1 << 1, // some controls activate on mouse up
-		B_ACTIVATED			= 1 << 2,
-		B_HOVER				= 1 << 3,
-		B_DISABLED			= 1 << 4,
-		B_DEFAULT_BUTTON	= 1 << 5,
-		B_IGNORE_OUTLINE	= 1 << 6,
+		B_FOCUSED				= 1 << 0,
+		B_CLICKED				= 1 << 1, // some controls activate on mouse up
+		B_ACTIVATED				= 1 << 2,
+		B_HOVER					= 1 << 3,
+		B_DISABLED				= 1 << 4,
+		B_DEFAULT_BUTTON		= 1 << 5,
+		B_IGNORE_OUTLINE		= 1 << 6,
+		B_PARTIALLY_ACTIVATED	= 1 << 7, // like B_ACTIVATED, but for tri-state
 
 		B_BLEND_FRAME		= 1 << 16
 	};

src/kits/interface/CheckBox.cpp

@@ -26,7 +26,8 @@ BCheckBox::BCheckBox(BRect frame, const char *name, const char *label,
 	:
 	BControl(frame, name, label, message, resizingMode, flags),
 	fPreferredSize(),
-	fOutlined(false)
+	fOutlined(false),
+	fPartialToOff(false)
 {
 	// Resize to minimum height if needed
 	font_height fontHeight;
@@ -43,7 +44,8 @@ BCheckBox::BCheckBox(const char *name, const char *label, BMessage *message,
 	:
 	BControl(name, label, message, flags | B_WILL_DRAW | B_NAVIGABLE),
 	fPreferredSize(),
-	fOutlined(false)
+	fOutlined(false),
+	fPartialToOff(false)
 {
 }
 
@@ -52,7 +54,8 @@ BCheckBox::BCheckBox(const char *label, BMessage *message)
 	:
 	BControl(NULL, label, message, B_WILL_DRAW | B_NAVIGABLE),
 	fPreferredSize(),
-	fOutlined(false)
+	fOutlined(false),
+	fPartialToOff(false)
 {
 }
 
@@ -60,7 +63,8 @@ BCheckBox::BCheckBox(const char *label, BMessage *message)
 BCheckBox::BCheckBox(BMessage *archive)
 	:
 	BControl(archive),
-	fOutlined(false)
+	fOutlined(false),
+	fPartialToOff(false)
 {
 }
 
@@ -322,7 +326,16 @@ BCheckBox::MessageReceived(BMessage *message)
 void
 BCheckBox::KeyDown(const char *bytes, int32 numBytes)
 {
-	BControl::KeyDown(bytes, numBytes);
+	if (*bytes == B_ENTER || *bytes == B_SPACE) {
+		if (!IsEnabled())
+			return;
+
+		SetValue(_NextState());
+		Invoke();
+	} else {
+		// skip the BControl implementation
+		BView::KeyDown(bytes, numBytes);
+	}
 }
 
 
@@ -360,7 +373,7 @@ BCheckBox::MouseDown(BPoint point)
 
 		if (fOutlined) {
 			fOutlined = false;
-			SetValue(!Value());
+			SetValue(_NextState());
 			Invoke();
 		} else {
 			Invalidate();
@@ -385,7 +398,7 @@ BCheckBox::MouseUp(BPoint point)
 
 	if (fOutlined) {
 		fOutlined = false;
-		SetValue(!Value());
+		SetValue(_NextState());
 		Invoke();
 	} else {
 		Invalidate();
@@ -485,8 +498,16 @@ BCheckBox::MakeFocus(bool focused)
 void
 BCheckBox::SetValue(int32 value)
 {
-	value = value ? B_CONTROL_ON : B_CONTROL_OFF;
-		// we only accept boolean values
+	// We only accept three possible values.
+	switch (value) {
+		case B_CONTROL_OFF:
+		case B_CONTROL_ON:
+		case B_CONTROL_PARTIALLY_ON:
+			break;
+		default:
+			value = B_CONTROL_ON;
+			break;
+	}
 
 	if (value != Value()) {
 		BControl::SetValueNoUpdate(value);
@@ -582,6 +603,20 @@ BCheckBox::LayoutInvalidated(bool descendants)
 }
 
 
+bool
+BCheckBox::IsPartialStateToOff() const
+{
+	return fPartialToOff;
+}
+
+
+void
+BCheckBox::SetPartialStateToOff(bool partialToOff)
+{
+	fPartialToOff = partialToOff;
+}
+
+
 // #pragma mark - FBC padding
 
 
@@ -625,6 +660,21 @@ BCheckBox::_ValidatePreferredSize()
 }
 
 
+int32
+BCheckBox::_NextState() const
+{
+	switch (Value()) {
+		case B_CONTROL_OFF:
+			return B_CONTROL_ON;
+		case B_CONTROL_PARTIALLY_ON:
+			return fPartialToOff ? B_CONTROL_OFF : B_CONTROL_ON;
+		case B_CONTROL_ON:
+		default:
+			return B_CONTROL_OFF;
+	}
+}
+
+
 BCheckBox &
 BCheckBox::operator=(const BCheckBox &)
 {

src/kits/interface/ControlLook.cpp

@@ -92,8 +92,14 @@ BControlLook::Flags(BControl* control) const
 		flags |= B_FOCUSED;
 	}
 
-	if (control->Value() == B_CONTROL_ON)
-		flags |= B_ACTIVATED;
+	switch (control->Value()) {
+		case B_CONTROL_ON:
+			flags |= B_ACTIVATED;
+			break;
+		case B_CONTROL_PARTIALLY_ON:
+			flags |= B_PARTIALLY_ACTIVATED;
+			break;
+	}
 
 	if (control->Parent() != NULL
 		&& (control->Parent()->Flags() & B_DRAW_ON_CHILDREN) != 0) {
@@ -3198,7 +3204,7 @@ bool
 BControlLook::_RadioButtonAndCheckBoxMarkColor(const rgb_color& base,
 	rgb_color& color, uint32 flags) const
 {
-	if ((flags & (B_ACTIVATED | B_CLICKED)) == 0) {
+	if ((flags & (B_ACTIVATED | B_PARTIALLY_ACTIVATED | B_CLICKED)) == 0) {
 		// no mark to be drawn at all
 		return false;
 	}
@@ -3212,12 +3218,15 @@ BControlLook::_RadioButtonAndCheckBoxMarkColor(const rgb_color& base,
 		mix = 0.4;
 	} else if ((flags & B_CLICKED) != 0) {
 		if ((flags & B_ACTIVATED) != 0) {
-			// loosing activation
+			// losing activation
 			mix = 0.7;
 		} else {
-			// becoming activated
+			// becoming activated (or losing partial activation)
 			mix = 0.3;
 		}
+	} else if ((flags & B_PARTIALLY_ACTIVATED) != 0) {
+		// partially activated
+		mix = 0.5;
 	} else {
 		// simply activated
 	}