Added font override mechanism

Author: Anuken

arc-core/src/arc/graphics/g2d/Font.java

@@ -555,6 +555,10 @@ public FontData(Fi fontFile, boolean flip){
             load(fontFile, flip);
         }
 
+        public void setOverride(FontData override){
+            //not implemented for non-freetype fonts
+        }
+
         public void addFallback(FontData data){
             //not implemented for non-freetype fonts
         }

extensions/freetype/src/arc/freetype/FreeTypeFontGenerator.java

@@ -691,6 +691,14 @@ public static class FreeTypeFontData extends FontData implements Disposable{
         Seq<Glyph> glyphs;
         private boolean dirty;
         Seq<FontData> fallback = new Seq<>();
+        @Nullable FontData override;
+
+        /** Sets a font to override the glyphs of this one, if they are available. This is the opposite of a fallback. */
+        @Override
+        public void setOverride(FontData override){
+            this.override = override;
+            override.capHeight = capHeight;
+        }
 
         @Override
         public void addFallback(FontData data){
@@ -701,6 +709,15 @@ public void addFallback(FontData data){
 
         @Override
         public Glyph getGlyph(char ch){
+            if(override != null){
+                Glyph result = override.getGlyph(ch);
+                if(result != override.missingGlyph){
+                    setGlyph(ch, result);
+                    dirty = true;
+                    return result;
+                }
+            }
+
             Glyph glyph = super.getGlyph(ch);
             if(glyph == null && generator != null){
                 generator.setPixelSizes(0, parameter.size);