Add option for presenting the web view share sheet modally

https://bugs.webkit.org/show_bug.cgi?id=246376
rdar://101050446

Reviewed by Aditya Keerthi.

Add an option to present the web view's share sheet modally instead of as a
popover.

* Source/WebKit/Platform/spi/ios/UIKitSPI.h:
* Source/WebKit/UIProcess/Cocoa/WKShareSheet.mm:
(-[WKShareSheet presentWithShareDataArray:inRect:]):

Canonical link: https://commits.webkit.org/255794@main

Source/WebKit/Platform/spi/ios/UIKitSPI.h

@@ -29,6 +29,7 @@
 
 #import <CoreSVG/CGSVGDocument.h>
 #import <UIKit/NSTextAlternatives.h>
+#import <UIKit/UIActivityViewController_Private.h>
 #import <UIKit/UIAlertController_Private.h>
 #import <UIKit/UIApplication_Private.h>
 #import <UIKit/UIBarButtonItem_Private.h>
@@ -737,6 +738,10 @@ typedef enum {
 - (UIWindow *)window;
 @end
 
+@interface UIActivityViewController ()
+@property (nonatomic) BOOL allowsCustomPresentationStyle;
+@end
+
 typedef NS_ENUM (NSInteger, _UIBackdropMaskViewFlags) {
     _UIBackdropMaskViewNone = 0,
     _UIBackdropMaskViewGrayscaleTint = 1 << 0,

Source/WebKit/UIProcess/Cocoa/WKShareSheet.mm

@@ -46,6 +46,10 @@
 #import <pal/spi/mac/NSSharingServicePickerSPI.h>
 #endif
 
+#if HAVE(UIKIT_WEBKIT_INTERNALS)
+#include <WebKitAdditions/WKShareSheetAdditions.h>
+#endif
+
 #if PLATFORM(IOS_FAMILY)
 
 @interface WKShareSheetFileItemProvider : UIActivityItemProvider
@@ -251,12 +255,20 @@ - (void)presentWithShareDataArray:(NSArray *)sharingItems inRect:(std::optional<
             [self dismiss];
     }];
 
-    UIPopoverPresentationController *popoverController = [_shareSheetViewController popoverPresentationController];
-    if (rect) {
-        popoverController.sourceView = webView;
-        popoverController.sourceRect = *rect;
+#if HAVE(UIKIT_WEBKIT_INTERNALS)
+    if (shareSheetUsesModalPresentationForWebView(webView)) {
+        [_shareSheetViewController setAllowsCustomPresentationStyle:YES];
+        [_shareSheetViewController setModalPresentationStyle:UIModalPresentationFormSheet];
     } else
-        popoverController._centersPopoverIfSourceViewNotSet = YES;
+#endif // HAVE(UIKIT_WEBKIT_INTERNALS)
+    {
+        UIPopoverPresentationController *popoverController = [_shareSheetViewController popoverPresentationController];
+        if (rect) {
+            popoverController.sourceView = webView;
+            popoverController.sourceRect = *rect;
+        } else
+            popoverController._centersPopoverIfSourceViewNotSet = YES;
+    }
 
     if ([_delegate respondsToSelector:@selector(shareSheet:willShowActivityItems:)])
         [_delegate shareSheet:self willShowActivityItems:sharingItems];