Setting the background picture position - objective-c

Question

Is there any Mac App Store compliant way of setting the desktop wallpaper position to "Stretch to Fill Screen"?

Answer 1

This code sample from Apple provides a good overview of the problem and how to properly code for it in Cocoa. The salient code snippet appears to be the following:
- (void)updateScreenOptions:(NSScreen*)screen
{
if (screen)
{
NSDictionary *screenOptions = [[NSWorkspace sharedWorkspace] desktopImageOptionsForScreen:curScreen];
// the value is an NSNumber containing an NSImageScaling (scaling factor)
NSNumber *scalingFactor = [screenOptions objectForKey:NSWorkspaceDesktopImageScalingKey];
[scalingPopup selectItemAtIndex:[scalingFactor integerValue]];
// the value is an NSNumber containing a BOOL (allow clipping)
NSNumber *allowClipping = [screenOptions objectForKey:NSWorkspaceDesktopImageAllowClippingKey];
[[clippingCheckbox cell] setState:[allowClipping boolValue]];
// the value is an NSColor (fill color)
NSColor *fillColorValue = [screenOptions objectForKey:NSWorkspaceDesktopImageFillColorKey];
if (fillColorValue)
[fillColor setColor:fillColorValue];
}
}
As mentioned in some of the answer errata, the correct method calls here to resolve your question appear to be [screenOptions setObject:scalingFactor forKey:NSWorkspaceDesktopImageScalingKey] and [[NSWorkspace sharedWorkspace] setDesktopImageURL:imageURL forScreen:curScreen options:screenOptions error:&error], which should provide the desired functionality.
I freely admit this was a collaborative effort, but it seems we've blundered through to a correct solution.
(Additional information on the NSImageScaling enumeration and NSWorkspace, which contains the correct scaling keys.)

Answer 2

Unfortunately there is no Mac App Store compliant way of setting the desktop image options. They only methods available with regards to desktop images are:
– desktopImageURLForScreen:
– setDesktopImageURL:forScreen:options:error:
– desktopImageOptionsForScreen:
You may be able to do it by executing an AppleScript, though I do not think Apple will like that.
Hope this helps!
EDIT:
[screenOptions setObject:scalingFactor forKey:NSWorkspaceDesktopImageScalingKey];
[[NSWorkspace sharedWorkspace] setDesktopImageURL:imageURL forScreen:curScreen options:screenOptions error:&error];