Change heaviness of NSWindow drop shadow? - macos

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.