SDL: dialog: fix default file name on Cocoa

SDL Commits
1 
From b2d152e51f6c0ac32b559335e0d0da3c8301f0c9 Mon Sep 17 00:00:00 2001
From: Anon Ymous <[EMAIL REDACTED]>
Date: Fri, 18 Jul 2025 00:45:42 +0530
Subject: [PATCH] dialog: fix default file name on Cocoa

---
 src/dialog/cocoa/SDL_cocoadialog.m | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/dialog/cocoa/SDL_cocoadialog.m b/src/dialog/cocoa/SDL_cocoadialog.m
index 671ca887c5bb6..4ae894cddff82 100644
--- a/src/dialog/cocoa/SDL_cocoadialog.m
+++ b/src/dialog/cocoa/SDL_cocoadialog.m
@@ -158,7 +158,14 @@ void SDL_SYS_ShowFileDialogWithProperties(SDL_FileDialogType type, SDL_DialogFil
     [dialog setAllowsOtherFileTypes:YES];
 
     if (default_location) {
-        [dialog setDirectoryURL:[NSURL fileURLWithPath:[NSString stringWithUTF8String:default_location]]];
+        char last = default_location[SDL_strlen(default_location) - 1];
+        NSURL* url = [NSURL fileURLWithPath:[NSString stringWithUTF8String:default_location]];
+        if (last == '/') {
+            [dialog setDirectoryURL:url];
+        } else {
+            [dialog setDirectoryURL:[url URLByDeletingLastPathComponent]];
+            [dialog setNameFieldStringValue:[url lastPathComponent]];
+        }
     }
 
     NSWindow *w = NULL;