Bug 286549 – [UnifiedPDF] Incremental PDF Loading should be used on iOS family

• Component: PDF
• Status: NEW

[Abrar Rahman Protyasha]

Currently, with UnifiedPDF enabled, we do not use incremental PDF loading on iOS family. This is because said loading path is gated behind HAVE(INCREMENTAL_PDF_APIS) platform availability. However, all of the following SPI (which the platform availability macro guards against) are available on the iOS family platforms.

```
// CoreGraphics

extern const off_t kCGDataProviderIndeterminateSize;
extern const CFStringRef kCGDataProviderHasHighLatency;

typedef void (*CGDataProviderGetByteRangesCallback)(void *info,
    CFMutableArrayRef buffers, const CFRange *ranges, size_t count);

struct CGDataProviderDirectAccessRangesCallbacks {
    unsigned version;
    CGDataProviderGetBytesAtPositionCallback getBytesAtPosition;
    CGDataProviderGetByteRangesCallback getBytesInRanges;
    CGDataProviderReleaseInfoCallback releaseInfo;
};
typedef struct CGDataProviderDirectAccessRangesCallbacks CGDataProviderDirectAccessRangesCallbacks;

extern void CGDataProviderSetProperty(CGDataProviderRef, CFStringRef key, CFTypeRef value);
extern CGDataProviderRef CGDataProviderCreateMultiRangeDirectAccess(
    void *info, off_t size,
    const CGDataProviderDirectAccessRangesCallbacks *);
```

```
// PDFKit

@interface PDFDocument ()
-(instancetype)initWithProvider:(CGDataProviderRef)dataProvider;
-(void)preloadDataOfPagesInRange:(NSRange)range onQueue:(dispatch_queue_t)queue completion:(void (^)(NSIndexSet* loadedPageIndexes))completionBlock;
-(void)resetFormFields:(PDFActionResetForm *) action;
@property (readwrite, nonatomic) BOOL hasHighLatencyDataProvider;
@end
```

As such, we should try flipping incremental PDF loading for that platform family.

[Radar WebKit Bug Importer]

<rdar://problem/143648895>

[Abrar Rahman Protyasha]

Pull request: https://github.com/WebKit/WebKit/pull/54893