Interface Kit: introduce B_TRANSPARENT_BACKGROUND flag

BeOS didn't support transparent views. As documented in the Be Book,
SetViewColor(B_TRANSPARENT_COLOR) only effect is to not fill the
invalidated areas with the view color before calling Draw() (it avoids
flickering, especially when combined with B_FULL_UPDATE_ON_RESIZE).

A previous change made B_TRANSPARENT_COLOR actually make the view
transparent (that is, additionally to the above, the underlying view is
drawn before the transparent children), but it creates compatibility
issues.

In order to keep the API compatible with BeOS, the new behavior is now
enabled explicitly using the B_TRANSPARENT_VIEW flag. This also opens
for future developments like allowing a view color with an alpha
channel (not supported yet).

Adjust programs that require transparent views.

Fixes #15744, #15745.
Helps with #15645.

Change-Id: I529574ea23db0a23579521b263bc8d572775e35a
Reviewed-on: https://review.haiku-os.org/c/haiku/+/2275
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>

headers/os/interface/View.h

@@ -80,6 +80,7 @@ const uint32 B_INPUT_METHOD_AWARE		= 0x00400000UL;	/* 23 */
 const uint32 B_SCROLL_VIEW_AWARE		= 0x00200000UL;	/* 22 */
 const uint32 B_SUPPORTS_LAYOUT			= 0x00100000UL;	/* 21 */
 const uint32 B_INVALIDATE_AFTER_LAYOUT	= 0x00080000UL;	/* 20 */
+const uint32 B_TRANSPARENT_BACKGROUND	= 0x00040000UL;	/* 19 */
 
 #define _RESIZE_MASK_ (0xffff)
 

src/apps/activitymonitor/ActivityView.cpp

@@ -613,6 +613,7 @@ ActivityView::_Init(const BMessage* settings)
 	fLegendLayoutItem = NULL;
 #endif
 	SetViewColor(B_TRANSPARENT_COLOR);
+	SetFlags(Flags() | B_TRANSPARENT_BACKGROUND);
 
 	fLastRefresh = 0;
 	fDrawResolution = 1;

src/apps/networkstatus/NetworkStatusView.cpp

@@ -94,7 +94,7 @@ signal_strength_compare(const wireless_network &a,
 NetworkStatusView::NetworkStatusView(BRect frame, int32 resizingMode,
 		bool inDeskbar)
 	: BView(frame, kDeskbarItemName, resizingMode,
-		B_WILL_DRAW | B_FRAME_EVENTS),
+		B_WILL_DRAW | B_TRANSPARENT_BACKGROUND | B_FRAME_EVENTS),
 	fInDeskbar(inDeskbar)
 {
 	_Init();

src/apps/powerstatus/PowerStatusView.cpp

@@ -66,7 +66,7 @@ PowerStatusView::PowerStatusView(PowerStatusDriverInterface* interface,
 	BRect frame, int32 resizingMode,  int batteryID, bool inDeskbar)
 	:
 	BView(frame, kDeskbarItemName, resizingMode,
-		B_WILL_DRAW | B_FULL_UPDATE_ON_RESIZE),
+		B_WILL_DRAW | B_TRANSPARENT_BACKGROUND | B_FULL_UPDATE_ON_RESIZE),
 	fDriverInterface(interface),
 	fBatteryID(batteryID),
 	fInDeskbar(inDeskbar)

src/kits/interface/Dragger.cpp

@@ -227,6 +227,7 @@ BDragger::AttachedToWindow()
 		SetLowColor(kZombieColor);
 		SetViewColor(kZombieColor);
 	} else {
+		SetFlags(Flags() | B_TRANSPARENT_BACKGROUND);
 		SetLowColor(B_TRANSPARENT_COLOR);
 		SetViewColor(B_TRANSPARENT_COLOR);
 	}

src/kits/interface/View.cpp

@@ -1050,7 +1050,8 @@ BView::SetFlags(uint32 flags)
 
 		uint32 changesFlags = flags ^ fFlags;
 		if (changesFlags & (B_WILL_DRAW | B_FULL_UPDATE_ON_RESIZE
-				| B_FRAME_EVENTS | B_SUBPIXEL_PRECISE)) {
+				| B_FRAME_EVENTS | B_SUBPIXEL_PRECISE
+				| B_TRANSPARENT_BACKGROUND)) {
 			_CheckLockAndSwitchCurrent();
 
 			fOwner->fLink->StartMessage(AS_VIEW_SET_FLAGS);

src/servers/app/View.cpp

@@ -486,7 +486,18 @@ View::SetName(const char* string)
 void
 View::SetFlags(uint32 flags)
 {
+	uint32 oldFlags = fFlags;
 	fFlags = flags;
+
+	// Child view with B_TRANSPARENT_BACKGROUND flag change clipping of
+	// parent view.
+	if (fParent != NULL
+		&& IsVisible()
+		&& (((oldFlags & B_TRANSPARENT_BACKGROUND) != 0)
+			!= ((fFlags & B_TRANSPARENT_BACKGROUND) != 0))) {
+		fParent->RebuildClipping(false);
+	}
+
 	fDrawState->SetSubPixelPrecise(fFlags & B_SUBPIXEL_PRECISE);
 }
 
@@ -717,7 +728,7 @@ View::ResizeBy(int32 x, int32 y, BRegion* dirtyRegion)
 				for (View* child = FirstChild(); child;
 						child = child->NextSibling()) {
 					if (!child->IsVisible()
-						|| child->fViewColor == B_TRANSPARENT_COLOR) {
+						|| (child->fFlags & B_TRANSPARENT_BACKGROUND) != 0) {
 						continue;
 					}
 					IntRect previousChildVisible(
@@ -923,22 +934,6 @@ View::CopyBits(IntRect src, IntRect dst, BRegion& windowContentClipping)
 // #pragma mark -
 
 
-void
-View::SetViewColor(const rgb_color& color)
-{
-	rgb_color oldColor = fViewColor;
-	fViewColor = color;
-	// Child view with B_TRANSPARENT_COLOR view color change clipping of
-	// parent view.
-	if (fParent != NULL
-		&& IsVisible()
-		&& ((oldColor == B_TRANSPARENT_COLOR)
-			!= (color == B_TRANSPARENT_COLOR))) {
-		fParent->RebuildClipping(false);
-	}
-}
-
-
 void
 View::ColorUpdated(color_which which, rgb_color color)
 {
@@ -1419,7 +1414,7 @@ View::RebuildClipping(bool deep)
 
 			for (; child; child = child->NextSibling()) {
 				if (child->IsVisible()
-					&& child->fViewColor != B_TRANSPARENT_COLOR) {
+					&& (child->fFlags & B_TRANSPARENT_BACKGROUND) == 0) {
 					childrenRegion->Include((clipping_rect)child->Frame());
 				}
 			}

src/servers/app/View.h

@@ -135,7 +135,8 @@ public:
 
 			const rgb_color& ViewColor() const
 								{ return fViewColor; }
-			void			SetViewColor(const rgb_color& color);
+			void			SetViewColor(const rgb_color& color)
+								{ fViewColor = color; }
 
 			void			ColorUpdated(color_which which, rgb_color color);
 			void			SetViewUIColor(color_which which, float tint);