implement file picker in iOS with .ext to UTI filtering

PanoPainter/GameViewController.m

@@ -12,6 +12,7 @@
 #include "app.h"
 #include "settings.h"
 #import "objc_utils.h"
+#import <MobileCoreServices/MobileCoreServices.h>
 
 std::mutex render_mutex;
 std::condition_variable render_cv;
@@ -25,6 +26,15 @@ std::condition_variable render_cv;
 @implementation GameImagePicker
 @end
 
+@interface GameFilePicker : UIDocumentPickerViewController
+{
+    @public std::promise<std::string> promise;
+    @public std::function<void(std::string)> callback;
+}
+@end
+@implementation GameFilePicker
+@end
+
 //std::map<
 bool pen_down = false;
 int t_count = 0;
@@ -152,15 +162,41 @@ std::recursive_mutex lock_mutex;
     GameImagePicker* p = static_cast<GameImagePicker*>(picker);
     std::string path = [chosenImage cStringUsingEncoding:NSUTF8StringEncoding];
     p->callback(path);
-    [picker dismissViewControllerAnimated:YES completion:^{
-                    [self keyboardWasHidden:nil];
-                }];
+    [picker dismissViewControllerAnimated:YES completion:NULL];
 }
 - (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker
 {
-    [picker dismissViewControllerAnimated:YES completion:^{
-                    [self keyboardWasHidden:nil];
-                }];
+    [picker dismissViewControllerAnimated:YES completion:NULL];
+}
+
+- (void)pick_file:(NSArray<NSString*>*)types then:(std::function<void(std::string)>)callback
+{
+    // convert extension into UTIs from the system database
+    NSMutableArray* UTIs = [NSMutableArray arrayWithCapacity:types.count];
+    for (NSString* ext : types)
+    {
+        NSString *typeForExt = (__bridge NSString*)
+            UTTypeCreatePreferredIdentifierForTag(kUTTagClassFilenameExtension,
+            (__bridge CFStringRef)ext, NULL);
+        [UTIs addObject:typeForExt];
+    }
+    
+    GameFilePicker *picker = [[GameFilePicker alloc] initWithDocumentTypes:UTIs inMode:UIDocumentPickerModeImport];
+    picker.delegate = self;
+    picker->callback = callback;
+    [self presentViewController:picker animated:YES completion:NULL];
+}
+-(void)documentPicker:(UIDocumentPickerViewController *)controller didPickDocumentAtURL:(NSURL *)url
+{
+    NSString *chosenImage = [url path];
+    GameFilePicker* p = static_cast<GameFilePicker*>(controller);
+    std::string path = [chosenImage cStringUsingEncoding:NSUTF8StringEncoding];
+    p->callback(path);
+    [controller dismissViewControllerAnimated:YES completion:NULL];
+}
+-(void)documentPickerWasCancelled:(UIDocumentPickerViewController *)controller
+{
+    [controller dismissViewControllerAnimated:YES completion:NULL];
 }
 
 - (void)insertText:(NSString *)text
@@ -185,7 +221,19 @@ std::recursive_mutex lock_mutex;
     return YES;
 }
 - (BOOL)canBecomeFirstResponder {
-    return YES;
+    return input_enabled;
+}
+
+-(void)show_keyboard
+{
+    input_enabled = YES;
+    [self becomeFirstResponder];
+}
+
+-(void)hide_keyboard
+{
+    input_enabled = NO;
+    [self resignFirstResponder];
 }
 
 // Call this method somewhere in your view controller setup code.
@@ -416,6 +464,7 @@ std::set<UITouch*> ignored_touch;
 - (void)viewDidLoad
 {
     [super viewDidLoad];
+    input_enabled = NO;
     App::I = new App;
     App::I->ios_view = self;
     App::I->initLog();