Work around CG assert drawing tiny glyphs.

For some fonts when drawing glyphs at CGFLOAT_MIN size,
CG will assert internally. Instead, request such glyphs at size 1,
and scale them down to 0 with a transform.

This change follows the pattern set by
3490263287e9432119c501884e45840de4d986bc
"Replace use of deprecated CG methods." on master.

BUG=chromium:441538
R=reed@google.com

Review URL: https://codereview.chromium.org/796783003

1 files changed, 5 insertions, 2 deletions

diff --git a/src/ports/SkFontHost_mac.cpp b/src/ports/SkFontHost_mac.cpp
index 2f991c861..8c1abc91c 100755
--- a/src/ports/SkFontHost_mac.cpp
+++ b/src/ports/SkFontHost_mac.cpp
@@ -741,9 +741,12 @@ SkScalerContext_Mac::SkScalerContext_Mac(SkTypeface_Mac* typeface,
     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));