Applied patch from engleek with fix hints from devheart (bug #4720):

Scale to fit now keeps the aspect ratio by cutting horizontally or vertically.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@40144 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/kits/tracker/BackgroundImage.cpp

@@ -199,7 +199,18 @@ BackgroundImage::Show(BackgroundImageInfo *info, BView *view)
 			// else fall thru
 		case kScaledToFit:
 			if (fIsDesktop) {
-				destinationBitmapBounds = viewBounds;
+				if (BRectRatio(destinationBitmapBounds)
+					>= BRectRatio(viewBounds)) {
+					float overlap = BRectHorizontalOverlap(viewBounds,
+						destinationBitmapBounds);
+					destinationBitmapBounds.Set(-overlap, 0,
+						viewBounds.Width() + overlap, viewBounds.Height());
+				} else {
+					float overlap = BRectVerticalOverlap(viewBounds,
+						destinationBitmapBounds);
+					destinationBitmapBounds.Set(0, -overlap,
+						viewBounds.Width(), viewBounds.Height() + overlap);
+				}
 				followFlags = B_FOLLOW_ALL;
 				break;
 			}
@@ -224,6 +235,30 @@ BackgroundImage::Show(BackgroundImageInfo *info, BView *view)
 	fShowingBitmap = info;
 }
 
+
+float
+BackgroundImage::BRectRatio(BRect rect)
+{
+	return rect.Width() / rect.Height();
+}
+
+
+float
+BackgroundImage::BRectHorizontalOverlap(BRect hostRect, BRect resizedRect)
+{
+	return ((hostRect.Height() / resizedRect.Height() * resizedRect.Width())
+		- hostRect.Width()) / 2;
+}
+
+
+float
+BackgroundImage::BRectVerticalOverlap(BRect hostRect, BRect resizedRect)
+{
+	return ((hostRect.Width() / resizedRect.Width() * resizedRect.Height())
+		- hostRect.Height()) / 2;
+}
+
+
 void 
 BackgroundImage::Remove()
 {

src/kits/tracker/BackgroundImage.h

@@ -115,6 +115,10 @@ private:
 
 	void Add(BackgroundImageInfo *);
 
+	float BRectRatio(BRect rect);
+	float BRectHorizontalOverlap(BRect hostRect, BRect resizedRect);
+	float BRectVerticalOverlap(BRect hostRect, BRect resizedRect);
+
 	bool fIsDesktop;
 	BNode fDefinedByNode;
 	BView *fView;

src/preferences/backgrounds/BackgroundImage.cpp

@@ -299,7 +299,18 @@ BackgroundImage::Show(BackgroundImageInfo* info, BView* view)
 			// else fall thru
 		case kScaledToFit:
 			if (fIsDesktop) {
-				destinationBitmapBounds = viewBounds;
+				if (BRectRatio(destinationBitmapBounds)
+					>= BRectRatio(viewBounds)) {
+					float overlap = BRectHorizontalOverlap(viewBounds,
+						destinationBitmapBounds);
+					destinationBitmapBounds.Set(-overlap, 0,
+						viewBounds.Width() + overlap, viewBounds.Height());
+				} else {
+					float overlap = BRectVerticalOverlap(viewBounds,
+						destinationBitmapBounds);
+					destinationBitmapBounds.Set(0, -overlap,
+						viewBounds.Width(), viewBounds.Height() + overlap);
+				}
 				followFlags = B_FOLLOW_ALL;
 				break;
 			}
@@ -334,6 +345,29 @@ BackgroundImage::Show(BackgroundImageInfo* info, BView* view)
 }
 
 
+float
+BackgroundImage::BRectRatio(BRect rect)
+{
+	return rect.Width() / rect.Height();
+}
+
+
+float
+BackgroundImage::BRectHorizontalOverlap(BRect hostRect, BRect resizedRect)
+{
+	return ((hostRect.Height() / resizedRect.Height() * resizedRect.Width())
+		- hostRect.Width()) / 2;
+}
+
+
+float
+BackgroundImage::BRectVerticalOverlap(BRect hostRect, BRect resizedRect)
+{
+	return ((hostRect.Width() / resizedRect.Width() * resizedRect.Height())
+		- hostRect.Height()) / 2;
+}
+
+
 void
 BackgroundImage::Remove()
 {

src/preferences/backgrounds/BackgroundImage.h

@@ -139,6 +139,10 @@ private:
 		// no public constructor, GetBackgroundImage factory function is
 		// used instead
 
+	float BRectRatio(BRect rect);
+	float BRectHorizontalOverlap(BRect hostRect, BRect resizedRect);
+	float BRectVerticalOverlap(BRect hostRect, BRect resizedRect);
+
 	bool fIsDesktop;
 	BNode fDefinedByNode;
 	BView* fView;