Work around CG assert drawing tiny glyphs.

src/ports/SkFontHost_mac.cpp

 
 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifdef SK_BUILD_FOR_MAC
 #import <ApplicationServices/ApplicationServices.h>
@@ skipping 723 matching lines @@
             CFDictionaryAddValue(cfAttributes, kCTFontOrientationAttribute, cfVertical);
             ctFontDesc.reset(CTFontDescriptorCreateWithAttributes(cfAttributes));
         }
     }
 
     // The transform contains everything except the requested text size.
     // Some properties, like 'trak', are based on the text size (before applying the matrix).
     CGFloat textSize = ScalarToCG(fRec.fTextSize);
 
     // If a text size of 0 is requested, CoreGraphics will use 12 instead.
-    // If the text size is 0, set it to something tiny.
+    // It would make sense to force the text size to something tiny,
+    // but this causes assertion failures inside CG (drawing glyphs at CGFLOAT_MIN size).
+    // Instead, set such tiny sizes to 1, and transform them down to 0 with a singular transform.
     if (textSize < CGFLOAT_MIN) {
-        textSize = CGFLOAT_MIN;
+        textSize = 1;
+        transform = CGAffineTransformMakeScale(0, 0);
     }
 
     fCTFont.reset(CTFontCreateCopyWithAttributes(ctFont, textSize, &transform, ctFontDesc));
     fCGFont.reset(CTFontCopyGraphicsFont(fCTFont, NULL));
     if (fVertical) {
         CGAffineTransform rotateLeft = CGAffineTransformMake(0, -1, 1, 0, 0, 0);
         transform = CGAffineTransformConcat(rotateLeft, transform);
         fCTVerticalFont.reset(CTFontCreateCopyWithAttributes(ctFont, textSize, &transform, NULL));
     }
 
@@ skipping 1497 matching lines @@
         }
         return face;
     }
 };
 
 ///////////////////////////////////////////////////////////////////////////////
 
 SkFontMgr* SkFontMgr::Factory() {
     return SkNEW(SkFontMgr_Mac);
 }