CoreText fallback shaper ex

More experimenting on top of https://github.com/rive-app/rive/pull/8556

This breaks some APIs that still need to be fixed up elsewhere.

The basic concept here is that when you request a system font you can tell it whether you're requesting to use it a Harfbuzz shaped system font or a CoreText (System) shaped system font.

We prioritize Harfbuzz first so that we have predictable performance and results across edit and runtime. To do this the fallback process now comes with an index. Iteration will keep happening until no font is returned (or all glyphs are found).

If the registered fallbacks look like this:
```
RiveFont.fallbackFonts = [
  UIFont(name: "PingFangSC-Semibold", size: 12)!,
  UIFont(name: "Hiragino Sans", size: 12)!
]
```

The fallback process will return:
```
iter 0: Ping Fang Harfbuzz Shaped
iter 1: Hiragino San Harfbuzz Shaped
iter 2: Ping Fang Coretext Shaped
iter 3: Hiragino Sans Coretext Shaped
```

We also use Coretext last as usually shaping with Coretext causes Apple's shaper to do its own fallbacks (it calls them cascades like css). So iter 2 (in the example above) will be the final iteration as all glyphs get filled via Apple's own fallbacks.

![CleanShot 2024-11-14 at 21 16 55@2x](https://github.com/user-attachments/assets/c12e158b-5b8e-41d4-8d9b-8184a316a079)

Diffs=
3eefba5039 CoreText fallback shaper ex (#8568)

Co-authored-by: David Skuza <[email protected]>
Co-authored-by: Luigi Rosso <[email protected]>

.rive_head

@@ -1 +1 @@
-807f9b20ac7f040df6646b808bdb70ab84b7db57
+3eefba5039d73329b31048b3bd839bfabc177bc0

Source/Renderer/RiveFactory.mm

@@ -19,7 +19,8 @@
 
 static NSArray<id<RiveFallbackFontProvider>>* _fallbackFonts = nil;
 
-static rive::rcp<rive::Font> riveFontFromNativeFont(id font)
+static rive::rcp<rive::Font> riveFontFromNativeFont(id font,
+                                                    bool useSystemShaper)
 {
     uint16_t weight = 400;
     if ([font conformsToProtocol:@protocol(RiveWeightProvider)])
@@ -34,24 +35,25 @@
     }
 
     CTFontRef ctFont = (__bridge CTFontRef)font;
-    return HBFont::FromSystem((void*)ctFont, weight, width);
+    return HBFont::FromSystem((void*)ctFont, useSystemShaper, weight, width);
 }
 
-static rive::rcp<rive::Font> findFallbackFont(
-    rive::Span<const rive::Unichar> missing)
+static rive::rcp<rive::Font> findFallbackFont(const rive::Unichar missing,
+                                              const uint32_t fallbackIndex)
 {
-    // For each descriptor…
-    for (id<RiveFallbackFontProvider> fallback in RiveFont.fallbackFonts)
+    // Try all the fallback fonts twice, first pass with harfbuzz and the second
+    // loop uses the system shaper.
+    if (fallbackIndex / 2 < RiveFont.fallbackFonts.count)
     {
-        auto font = riveFontFromNativeFont(fallback.fallbackFont);
-        if (font->hasGlyph(missing))
-        {
-            rive::rcp<rive::Font> rcFont = rive::rcp<rive::Font>(font);
-            // because the font was released at load time, we need to give it an
-            // extra ref whenever we bump it to a reference counted pointer.
-            rcFont->ref();
-            return rcFont;
-        }
+        auto f =
+            [RiveFont
+                    .fallbackFonts[fallbackIndex % RiveFont.fallbackFonts.count]
+                fallbackFont];
+        auto font = riveFontFromNativeFont(
+            f, fallbackIndex >= RiveFont.fallbackFonts.count);
+        rive::rcp<rive::Font> rcFont = rive::rcp<rive::Font>(font);
+        rcFont->ref();
+        return rcFont;
     }
     return nullptr;
 }
@@ -194,12 +196,12 @@ - (RiveFont*)decodeFont:(nonnull NSData*)data
 #if TARGET_OS_IPHONE
 - (RiveFont*)decodeUIFont:(UIFont*)font
 {
-    return [[RiveFont alloc] initWithFont:riveFontFromNativeFont(font)];
+    return [[RiveFont alloc] initWithFont:riveFontFromNativeFont(font, true)];
 }
 #else
 - (RiveFont*)decodeNSFont:(NSFont*)font
 {
-    return [[RiveFont alloc] initWithFont:riveFontFromNativeFont(font)];
+    return [[RiveFont alloc] initWithFont:riveFontFromNativeFont(font, true)];
 }
 #endif