* Implemented preloading of the images around he current one; always two in the

direction of the current navigation, and one in the opposite direction.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@39377 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/apps/showimage/ImageCache.h

@@ -42,8 +42,9 @@ class ImageCache {
 public:
 	static	ImageCache&			Default() { return sCache; }
 
-			status_t			RetrieveImage(const entry_ref& ref, int32 page,
-									const BMessenger* target);
+			status_t			RetrieveImage(const entry_ref& ref,
+									int32 page = 1,
+									const BMessenger* target = NULL);
 
 private:
 								ImageCache();

src/apps/showimage/ImageFileNavigator.cpp

@@ -470,6 +470,21 @@ ImageFileNavigator::HasPreviousFile()
 }
 
 
+bool
+ImageFileNavigator::GetNextFile(const entry_ref& ref, entry_ref& nextRef)
+{
+	return fNavigator->FindNextImage(ref, nextRef, true, false);
+}
+
+
+bool
+ImageFileNavigator::GetPreviousFile(const entry_ref& ref,
+	entry_ref& previousRef)
+{
+	return fNavigator->FindNextImage(ref, previousRef, false, false);
+}
+
+
 /*!	Moves the current file into the trash.
 	Returns true if a new file should be loaded, false if not.
 */

src/apps/showimage/ImageFileNavigator.h

@@ -51,6 +51,11 @@ public:
 			bool				HasNextFile();
 			bool				HasPreviousFile();
 
+			bool				GetNextFile(const entry_ref& ref,
+									entry_ref& nextRef);
+			bool				GetPreviousFile(const entry_ref& ref,
+									entry_ref& previousRef);
+
 			bool				MoveFileToTrash();
 
 private:

src/apps/showimage/ShowImageWindow.cpp

@@ -702,7 +702,7 @@ ShowImageWindow::MessageReceived(BMessage* message)
 
 		case MSG_FILE_PREV:
 			if (_ClosePrompt() && fNavigator.PreviousFile())
-				_LoadImage();
+				_LoadImage(false);
 			break;
 
 		case MSG_FILE_NEXT:
@@ -976,11 +976,37 @@ ShowImageWindow::_ClosePrompt()
 
 
 status_t
-ShowImageWindow::_LoadImage()
+ShowImageWindow::_LoadImage(bool forward)
 {
 	BMessenger us(this);
-	return ImageCache::Default().RetrieveImage(fNavigator.CurrentRef(),
-		fNavigator.CurrentPage(), &us);
+	status_t status = ImageCache::Default().RetrieveImage(
+		fNavigator.CurrentRef(), fNavigator.CurrentPage(), &us);
+	if (status != B_OK)
+		return status;
+
+	// Preload previous/next images - two in the navigation direction, one
+	// in the opposite direction.
+
+	entry_ref nextRef = fNavigator.CurrentRef();
+	if (_PreloadImage(forward, nextRef))
+		_PreloadImage(forward, nextRef);
+
+	entry_ref previousRef = fNavigator.CurrentRef();
+	_PreloadImage(!forward, previousRef);
+
+	return B_OK;
+}
+
+
+bool
+ShowImageWindow::_PreloadImage(bool forward, entry_ref& ref)
+{
+	entry_ref currentRef = ref;
+	if ((forward && !fNavigator.GetNextFile(currentRef, ref))
+		|| (!forward && !fNavigator.GetPreviousFile(currentRef, ref)))
+		return false;
+
+	return ImageCache::Default().RetrieveImage(ref) == B_OK;
 }
 
 

src/apps/showimage/ShowImageWindow.h

@@ -64,7 +64,8 @@ private:
 			void				_SaveToFile(BMessage* message);
 									// Handle save file panel message
 			bool				_ClosePrompt();
-			status_t			_LoadImage();
+			status_t			_LoadImage(bool forward = true);
+			bool				_PreloadImage(bool forward, entry_ref& ref);
 			void				_ToggleFullScreen();
 			void				_ApplySettings();
 			void				_SavePrintOptions();