tighten up device bounds for glyphs

Change-Id: I61655b9492bdaacc2c1d5c7631b2e67af2b46668
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/335280
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>

Author: herbderby

src/gpu/text/GrTextBlob.cpp

@@ -524,6 +524,9 @@ GrSubRun* DirectMaskSubRun::Make(const SkZip<SkGlyphVariant, SkPoint>& drawables
     GlyphVector::Variant* glyphIDs =
             alloc->makeArray<GlyphVector::Variant>(drawables.size());
 
+    // The lower bounds of drawing is always (0, 0). Since glyphs from the atlas can be at most
+    // 256x256, use kMinPos to eliminate glyphs that have no pixels on the device.
+    constexpr SkScalar kMinPos = 0 - SkStrikeCommon::kSkSideTooBigForAtlas;
     // Because this is the direct case, the maximum width or height is the size that fits in the
     // atlas. This boundary is checked below to ensure that the call to SkGlyphRect below will
     // not overflow.
@@ -536,7 +539,7 @@ GrSubRun* DirectMaskSubRun::Make(const SkZip<SkGlyphVariant, SkPoint>& drawables
         // Ensure that the .offset() call below does not overflow. And, at this point none of the
         // rectangles are empty because they were culled before the run was created. Basically,
         // cull all the glyphs that can't appear on the screen.
-        if (-kMaxPos < x && x < kMaxPos && -kMaxPos  < y && y < kMaxPos) {
+        if (kMinPos < x && x < kMaxPos && kMinPos  < y && y < kMaxPos) {
             const SkGlyph* const skGlyph = variant;
             const SkGlyphRect deviceBounds =
                     skGlyph->glyphRect().offset(SkScalarRoundToInt(x), SkScalarRoundToInt(y));