fix(ios): apply obliqueness if italics are not supported (#745)

# Summary

this fixes #739 

- now `NSObliqueness` attribute is applied, when given font does not
support proper italics
- added `stylingPriority` trait for base styles, so italics can be
applied last

## Test Plan

Paste some non-latin characters, e.g. "冰淇淋", apply the italic style,
everything should look as expected

## Screenshots / Videos

The italics are now properly applied



https://github.com/user-attachments/assets/ed73f153-98b6-4d6c-bb2b-7d17eed75c25



## Compatibility

| OS      | Implemented |
| ------- | :---------: |
| iOS     |    ✅     |
| Android |    ❌     |
| Web     |    ❌     |

## Checklist

- [x] E2E tests are passing
- [ ] Required E2E tests have been added (if applicable)

---------

Co-authored-by: Mikołaj Szydłowski <9szydlowski9@gmail.com>

Author: hejsztynx

.maestro/enrichedInput/screenshots/ios/inline_styles_merge.png

@@ -0,0 +1,6 @@
+#import <Foundation/Foundation.h>
+#pragma once
+
+@interface NSArray (ArrayExtension)
+- (NSArray *)sortedArrayBySortKey:(NSInteger (^)(id item))sortKeyForItem;
+@end

.maestro/enrichedInput/screenshots/ios/inline_styles_removal.png

@@ -0,0 +1,18 @@
+#import "ArrayExtension.h"
+
+@implementation NSArray (ArrayExtension)
+
+- (NSArray *)sortedArrayBySortKey:(NSInteger (^)(id item))sortKeyForItem {
+  return [self sortedArrayWithOptions:NSSortStable
+                      usingComparator:^NSComparisonResult(id a, id b) {
+                        NSInteger aKey = sortKeyForItem(a);
+                        NSInteger bKey = sortKeyForItem(b);
+                        if (aKey == bKey) {
+                          return NSOrderedSame;
+                        }
+                        return aKey < bKey ? NSOrderedAscending
+                                           : NSOrderedDescending;
+                      }];
+}
+
+@end

ios/extensions/ArrayExtension.h

@@ -8,4 +8,5 @@
 - (UIFont *)setItalic;
 - (UIFont *)withFontTraits:(UIFont *)from;
 - (UIFont *)setSize:(CGFloat)size;
+- (BOOL)coversCharacters:(const unichar *)chars count:(CFIndex)count;
 @end

ios/extensions/ArrayExtension.mm

@@ -1,4 +1,5 @@
 #import "FontExtension.h"
+#import <CoreText/CoreText.h>
 #import <React/RCTLog.h>
 
 @implementation UIFont (FontExtension)
@@ -40,8 +41,6 @@ - (UIFont *)setItalic {
   if (fontDescriptor != nullptr) {
     return [UIFont fontWithDescriptor:fontDescriptor size:0];
   } else {
-    RCTLogWarn(
-        @"[EnrichedTextInput]: Couldn't apply italic trait to the font.");
     return self;
   }
 }
@@ -69,4 +68,10 @@ - (UIFont *)setSize:(CGFloat)size {
   }
 }
 
+- (BOOL)coversCharacters:(const unichar *)chars count:(CFIndex)count {
+  CGGlyph glyphs[2] = {0, 0};
+  return CTFontGetGlyphsForCharacters((__bridge CTFontRef)self, chars, glyphs,
+                                      count);
+}
+
 @end

ios/extensions/FontExtension.h

@@ -1,10 +1,12 @@
 #import "InputAttributesManager.h"
 #import "AlignmentUtils.h"
+#import "ArrayExtension.h"
 #import "AttributeEntry.h"
 #import "EnrichedTextInputView.h"
 #import "ParagraphAttributesUtils.h"
 #import "RangeUtils.h"
 #import "StyleHeaders.h"
+#import "StyleUtils.h"
 #import "ZeroWidthSpaceUtils.h"
 
 @implementation InputAttributesManager {
@@ -99,15 +101,11 @@ - (void)handleDirtyRangesStyling {
 
     // Sort style types so paragraph styles come first. Their broad visual
     // attributes (e.g. foreground color, font) are laid down before inline
-    // styles override them on their specific sub-ranges.
+    // styles override them on their specific sub-ranges. Inline styles among
+    // themselves follow their stylePriority.
     NSArray *sortedStyleTypes = [presentStyles.allKeys
-        sortedArrayUsingComparator:^NSComparisonResult(NSNumber *a,
-                                                       NSNumber *b) {
-          BOOL aPara = [_input->stylesDict[a] isParagraph];
-          BOOL bPara = [_input->stylesDict[b] isParagraph];
-          if (aPara == bPara)
-            return NSOrderedSame;
-          return aPara ? NSOrderedAscending : NSOrderedDescending;
+        sortedArrayBySortKey:^NSInteger(NSNumber *styleType) {
+          return [_input->stylesDict[styleType] stylePriority];
         }];
 
     // re-apply meta-attributes and apply visual styling following the saved

ios/extensions/FontExtension.mm

@@ -14,6 +14,7 @@
 - (BOOL)isParagraph;
 - (BOOL)needsZWS;
 - (BOOL)appliesStylingToTyping;
+- (NSInteger)stylePriority;
 - (instancetype)initWithHost:(id<EnrichedViewHost>)host;
 - (NSRange)actualUsedRange:(NSRange)range;
 - (void)toggle:(NSRange)range;

ios/inputAttributesManager/InputAttributesManager.mm

@@ -45,6 +45,11 @@ - (BOOL)appliesStylingToTyping {
   return NO;
 }
 
+// determines the order in which the styles are applied
+- (NSInteger)stylePriority {
+  return [self isParagraph] ? 0 : 2;
+}
+
 - (instancetype)initWithHost:(id<EnrichedViewHost>)host {
   self = [super init];
   _host = host;

ios/interfaces/StyleBase.h

@@ -1,5 +1,5 @@
 #import "EnrichedTextInputView.h"
-#import "FontExtension.h"
+#import "ItalicUtils.h"
 #import "StyleHeaders.h"
 
 @implementation ItalicStyle : StyleBase
@@ -16,21 +16,33 @@ - (BOOL)isParagraph {
   return NO;
 }
 
+// some styles might apply a new font (inline code), so we need to apply
+// the italic last, that way we know if the used font supports italics
+// or we need to apply a slant
+- (NSInteger)stylePriority {
+  return 3;
+}
+
 - (void)applyStyling:(NSRange)range {
+  if (self.host.textView.textStorage == nullptr || range.length == 0 ||
+      NSMaxRange(range) > self.host.textView.textStorage.length) {
+    return;
+  }
+
+  // we process each present font
   [self.host.textView.textStorage
       enumerateAttribute:NSFontAttributeName
                  inRange:range
                  options:0
-              usingBlock:^(id _Nullable value, NSRange range,
+              usingBlock:^(id _Nullable value, NSRange fontRange,
                            BOOL *_Nonnull stop) {
                 UIFont *font = (UIFont *)value;
-                if (font != nullptr) {
-                  UIFont *newFont = [font setItalic];
-                  [self.host.textView.textStorage
-                      addAttribute:NSFontAttributeName
-                             value:newFont
-                             range:range];
+                if (font == nullptr) {
+                  return;
                 }
+                [ItalicUtils applyItalicForFont:font
+                                  inTextStorage:self.host.textView.textStorage
+                                        inRange:fontRange];
               }];
 }