Fix #8881: Add color drops to Backgrounds

- The Backgrounds preferences app will now accept color drops.
- The Backgrounds app will update if a color drop to the desktop
has changed its color due to a direct color drop

Signed-off-by: Jerome Duval <jerome.duval@gmail.com>

src/kits/tracker/DeskWindow.cpp

@@ -39,6 +39,7 @@ All rights reserved.
 #include <Debug.h>
 #include <FindDirectory.h>
 #include <Locale.h>
+#include <Messenger.h>
 #include <NodeMonitor.h>
 #include <Path.h>
 #include <PathFinder.h>
@@ -641,6 +642,14 @@ BDeskWindow::MessageReceived(BMessage* message)
 			BScreen(this).SetDesktopColor(*color);
 			fPoseView->SetViewColor(*color);
 			fPoseView->SetLowColor(*color);
+
+			// Notify the backgrounds app that the background changed
+			status_t initStatus;
+			BMessenger messenger("application/x-vnd.Haiku-Backgrounds", -1,
+				&initStatus);
+			if (initStatus == B_OK)
+				messenger.SendMessage(message);
+
 			return;
 		}
 	}

src/preferences/backgrounds/Backgrounds.cpp

@@ -30,6 +30,7 @@ public:
 							BackgroundsWindow();
 
 			void			RefsReceived(BMessage* message);
+			void			MessageReceived(BMessage* message);
 
 protected:
 	virtual	bool			QuitRequested();
@@ -67,6 +68,14 @@ BackgroundsApplication::BackgroundsApplication()
 void
 BackgroundsApplication::MessageReceived(BMessage* message)
 {
+	const void *data;
+	ssize_t size;
+	if (message->WasDropped() && message->FindData("RGBColor", B_RGB_COLOR_TYPE,
+			&data, &size) == B_OK) {
+		// This is the desktop telling us that it was changed by a color drop
+		BMessenger(fWindow).SendMessage(message);
+		return;
+	}
 	switch (message->what) {
 		case B_SILENT_RELAUNCH:
 			fWindow->Activate();
@@ -116,6 +125,13 @@ BackgroundsWindow::RefsReceived(BMessage* message)
 }
 
 
+void
+BackgroundsWindow::MessageReceived(BMessage* message)
+{
+	BMessenger(fBackgroundsView).SendMessage(message);
+}
+
+
 bool
 BackgroundsWindow::QuitRequested()
 {

src/preferences/backgrounds/BackgroundsView.cpp

@@ -293,6 +293,19 @@ BackgroundsView::AllAttached()
 void
 BackgroundsView::MessageReceived(BMessage* message)
 {
+	// Color drop
+	if (message->WasDropped()) {
+		rgb_color *clr;
+		ssize_t out_size;
+		if (message->FindData("RGBColor", B_RGB_COLOR_TYPE,
+			(const void **)&clr, &out_size) == B_OK) {
+			fPicker->SetValue(*clr);
+			_UpdatePreview();
+			_UpdateButtons();
+			return;
+		}
+	}
+
 	switch (message->what) {
 		case B_SIMPLE_DATA:
 		case B_REFS_RECEIVED: