Simplify mask/clip intersection, making sure to explicitly check for an empty mask.

tests/DrawTextTest.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBitmap.h"
 #include "SkCanvas.h"
 #include "SkColor.h"
 #include "SkPaint.h"
 #include "SkPoint.h"
 #include "SkRect.h"
+#include "SkSurface.h"
 #include "SkTypes.h"
 #include "Test.h"
+#include <math.h>
 
 static const SkColor bgColor = SK_ColorWHITE;
 
 static void create(SkBitmap* bm, SkIRect bound) {
     bm->allocN32Pixels(bound.width(), bound.height());
 }
 
 static void drawBG(SkCanvas* canvas) {
     canvas->drawColor(bgColor);
 }
@@ skipping 78 matching lines @@
 
                         REPORTER_ASSERT(reporter,
                                         compare(drawTextBitmap, drawTextRect,
                                                 drawPosTextBitmap, drawPosTextRect));
                     }
                 }
             }
         }
     }
 }
+
+// Test drawing text at some unusual coordinates.
+// We measure success by not crashing or asserting.
+DEF_TEST(DrawText_weirdCoordinates, r) {
+    auto surface = SkSurface::MakeRasterN32Premul(10,10);
+    auto canvas = surface->getCanvas();
+
+    SkScalar oddballs[] = { 0.0f, (float)INFINITY, (float)NAN, 34359738368.0f };
+
+    for (auto x : oddballs) {
+        canvas->drawText("a", 1, +x, 0.0f, SkPaint());
+        canvas->drawText("a", 1, -x, 0.0f, SkPaint());
+    }
+    for (auto y : oddballs) {
+        canvas->drawText("a", 1, 0.0f, +y, SkPaint());
+        canvas->drawText("a", 1, 0.0f, -y, SkPaint());
+    }
+}