Change random number generator for tests to SkMWCRandom

Change random number generator for tests to SkMWCRandom.

Subject pretty much says it all. This also removes some unused headers and fixes a couple of bugs exposed by changing the random number generator.

First, the function SkMatrix::getMaxStretch() had an error where it was testing the square of a number against near-zero. This led to it occasionally taking a cheaper but imprecise path for computing the eigenvalues of the matrix. I replaced this with a check against the square of SK_ScalarNearlyZero. This does become a constant in assembly, at least on Windows.

The second case was a failure in ClipStackTest, where it hit the rare case of a practically empty clip stack (it has a single Union) and we set a tight bounds. The bounds rect doesn't get set by GrReducedClip::ReduceClipStack() in this case, so when it clips the reduced stack it's clipping against garbage, and the resulting regions don't match. The solution is to initialize the tightBounds rect.

[bsalomon, 2013-02-27 19:48:09]

On 2013/02/27 19:34:38, JimVV wrote:

lgtm

[commit-bot: I haz the power, 2013-02-28 19:02:44]

CQ is trying da patch. Follow status at
https://skia-tree-status.appspot.com/cq/jvanverth@google.com/12334131/1

[commit-bot: I haz the power, 2013-02-28 19:02:56]

Failed to apply patch for tests/PictureTest.cpp:
While running patch -p0 --forward --force --no-backup-if-mismatch;
  patching file tests/PictureTest.cpp
  Hunk #4 FAILED at 280.
  1 out of 5 hunks FAILED -- saving rejects to file tests/PictureTest.cpp.rej

Patch:       tests/PictureTest.cpp
Index: tests/PictureTest.cpp
===================================================================
--- tests/PictureTest.cpp	(revision 7881)
+++ tests/PictureTest.cpp	(working copy)
@@ -73,7 +73,7 @@
     return pic;
 }
 
-static void rand_rect(SkRect* rect, SkRandom& rand, SkScalar W, SkScalar H) {
+static void rand_rect(SkRect* rect, SkMWCRandom& rand, SkScalar W, SkScalar H)
{
     rect->fLeft   = rand.nextRangeScalar(-W, 2*W);
     rect->fTop    = rand.nextRangeScalar(-H, 2*H);
     rect->fRight  = rect->fLeft + rand.nextRangeScalar(0, W);
@@ -176,7 +176,7 @@
         drawbitmap_proc, drawbitmaprect_proc, drawshader_proc
     };
 
-    SkRandom rand;
+    SkMWCRandom rand;
     for (size_t k = 0; k < SK_ARRAY_COUNT(procs); ++k) {
         SkAutoTUnref<SkPicture> pic(record_bitmaps(bm, pos, N, procs[k]));
 
@@ -259,7 +259,7 @@
 }
 #endif
 
-static void rand_op(SkCanvas* canvas, SkRandom& rand) {
+static void rand_op(SkCanvas* canvas, SkMWCRandom& rand) {
     SkPaint paint;
     SkRect rect = SkRect::MakeWH(50, 50);
 
@@ -280,10 +280,10 @@
 }
 
 static void test_peephole(skiatest::Reporter* reporter) {
-    SkRandom rand;
+    SkMWCRandom rand;
 
     for (int j = 0; j < 100; j++) {
-        SkRandom rand2(rand.getSeed()); // remember the seed
+        SkMWCRandom rand2(rand); // remember the seed
 
         SkPicture picture;
         SkCanvas* canvas = picture.beginRecording(100, 100);
@@ -292,6 +292,8 @@
             rand_op(canvas, rand);
         }
         picture.endRecording();
+
+        rand = rand2;
     }
 
     {

[jvanverth1, 2013-03-04 13:58:30]

Committed as r7952.