Change heaviness of NSWindow drop shadow?

Question

I have an NSWindow that has a drop shadow, but it is way to dark. The shadow spreads too far and is too heavy for me. It's the default shadow for the NSWindow and I haven't edited it at all.

What I want to know is if there is a way to shorten the blur radius or lower the heaviness of the drop shadow so it appears a bit more subtle.

Thanks!

Answer 1

There's no public API, but you can do It by swizzling some methods on NSThemeFrame (this is the view class responsible for the window's frame, border, etc).

Here's an example ( a subclass of NSWindow ):

#import <objc/runtime.h>

@interface SOWindow : NSWindow
@end

@interface SOWindowThemeFrameOverrides : NSView
@end

@implementation SOWindow

+ (void)load
{
    NSArray *methodsToOverride = @[@"_shadowOffset", @"_shadowFlags", @"_shadowType"];
    for (NSString *selector in methodsToOverride) {
        Method m = class_getInstanceMethod(NSClassFromString(@"NSThemeFrame"), NSSelectorFromString(selector));
        Method m2 = class_getInstanceMethod([SOWindowThemeFrameOverrides class], NSSelectorFromString(selector));
        class_addMethod(NSClassFromString(@"NSThemeFrame"), NSSelectorFromString([NSString stringWithFormat:@"_original%@", selector]), method_getImplementation(m), method_getTypeEncoding(m));
        method_exchangeImplementations(m, m2);
    }
}

@end

@implementation SOWindowThemeFrameOverrides

- (NSSize)_shadowOffset
{
    if ([self.window isKindOfClass:[SOWindow class]]) {
        return NSMakeSize(0, 8);
    } else {
        return [self _original_shadowOffset];
    }
}

- (NSUInteger)_shadowFlags
{
    if ([self.window isKindOfClass:[SOWindow class]]) {
        return 0;
    } else {
        return [self _original_shadowFlags];
    }
}

- (NSInteger)_shadowType
{
    if ([self.window isKindOfClass:[SOWindow class]]) {
        return 4;
    } else {
        return [self _original_shadowType];
    }
}

#pragma mark Placeholder methods

- (NSSize)_original_shadowOffset
{
    // implementation will be filled in at runtime
    return NSZeroSize;
}

- (NSUInteger)_original_shadowFlags
{
    // implementation will be filled in at runtime
    return 0;
}

- (NSInteger)_original_shadowType
{
    // implementation will be filled in at runtime
    return 0;
}

@end

When the SOWindow class is loaded by the runtime, the + load method is invoked. The method switches NSThemeFrame's implementation of the 3 shadow methods by their implementation in SOWindowThemeFrameOverrides , also adding the original methods to the class with the _original prefix.

When the swizzled methods are called, we check to see if the window is a SOWindow , if It is we use the custom shadow, if It's not we forward the call to the original implementations.

This is what I get by returning 4 from _shadowType :

Please note that this is a huge hack and would probably be rejected if you tried to submit It to the AppStore.