allow subpixel positioning w/ bitmap filtering

tests/DrawBitmapRectTest.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 "SkData.h"
@@ skipping 76 matching lines @@
     size->set(rand.nextU() & 0xFFFF, rand.nextU() & 0xFFFF);
 }
 
 static bool treat_as_sprite(const SkMatrix& mat, const SkISize& size,
                             unsigned bits) {
     return SkTreatAsSprite(mat, size.width(), size.height(), bits);
 }
 
 static void test_treatAsSprite(skiatest::Reporter* reporter) {
     const unsigned bilerBits = kSkSubPixelBitsForBilerp;
+    const unsigned nearestNeighborBits = 0;
 
     SkMatrix mat;
     SkISize  size;
     SkRandom rand;
 
     // assert: translate-only no-filter can always be treated as sprite
     for (int i = 0; i < 1000; ++i) {
         rand_matrix(&mat, rand, SkMatrix::kTranslate_Mask);
         for (int j = 0; j < 1000; ++j) {
             rand_size(&size, rand);
@@ skipping 21 matching lines @@
 
     const SkScalar tinySubPixel = 100.02f;
     mat.setTranslate(tinySubPixel, 0);
     REPORTER_ASSERT(reporter, treat_as_sprite(mat, size, bilerBits));
     mat.setTranslate(0, tinySubPixel);
     REPORTER_ASSERT(reporter, treat_as_sprite(mat, size, bilerBits));
 
     const SkScalar twoThirds = SK_Scalar1 * 2 / 3;
     const SkScalar bigScale = SkScalarDiv(size.width() + twoThirds, size.width());
     mat.setScale(bigScale, bigScale);
-    REPORTER_ASSERT(reporter, !treat_as_sprite(mat, size, false));
+    REPORTER_ASSERT(reporter, !treat_as_sprite(mat, size, nearestNeighborBits));
     REPORTER_ASSERT(reporter, !treat_as_sprite(mat, size, bilerBits));
 
     const SkScalar oneThird = SK_Scalar1 / 3;
     const SkScalar smallScale = SkScalarDiv(size.width() + oneThird, size.width());
     mat.setScale(smallScale, smallScale);
-    REPORTER_ASSERT(reporter, treat_as_sprite(mat, size, false));
+    REPORTER_ASSERT(reporter, treat_as_sprite(mat, size, nearestNeighborBits));
     REPORTER_ASSERT(reporter, !treat_as_sprite(mat, size, bilerBits));
 
     const SkScalar oneFortyth = SK_Scalar1 / 40;
     const SkScalar tinyScale = SkScalarDiv(size.width() + oneFortyth, size.width());
     mat.setScale(tinyScale, tinyScale);
-    REPORTER_ASSERT(reporter, treat_as_sprite(mat, size, false));
+    REPORTER_ASSERT(reporter, treat_as_sprite(mat, size, nearestNeighborBits));
     REPORTER_ASSERT(reporter, treat_as_sprite(mat, size, bilerBits));
 }
 
 static void assert_ifDrawnTo(skiatest::Reporter* reporter,
                              const SkBitmap& bm, bool shouldBeDrawn) {
     for (int y = 0; y < bm.height(); ++y) {
         for (int x = 0; x < bm.width(); ++x) {
             if (shouldBeDrawn) {
                 if (SK_ColorTRANSPARENT == *bm.getAddr32(x, y)) {
                     REPORTER_ASSERT(reporter, false);
@@ skipping 119 matching lines @@
         const uint8_t* ptr = reinterpret_cast<const uint8_t*>(bm.getAddr(0, y));
         for (size_t i = 0; i < count; i++) {
             if (ptr[i]) {
                 return false;
             }
         }
     }
     return true;
 }
 
+static void test_on_grid(skiatest::Reporter* reporter, int w, int h, const SkRect& r,
+                         SkScalar delta, int bits, bool expected) {
+    REPORTER_ASSERT(reporter, SkRectIsOnGrid(w, h, r.makeInset(delta, 0), bits) == expected);
+    REPORTER_ASSERT(reporter, SkRectIsOnGrid(w, h, r.makeInset(-delta, 0), bits) == expected);
+    REPORTER_ASSERT(reporter, SkRectIsOnGrid(w, h, r.makeInset(0, delta), bits) == expected);
+    REPORTER_ASSERT(reporter, SkRectIsOnGrid(w, h, r.makeInset(0, -delta), bits) == expected);
+
+    if (0 == bits) {
+        expected = true;
+    }
+    REPORTER_ASSERT(reporter, SkRectIsOnGrid(w, h, r.makeOffset(delta, 0), bits) == expected);
+    REPORTER_ASSERT(reporter, SkRectIsOnGrid(w, h, r.makeOffset(-delta, 0), bits) == expected);
+    REPORTER_ASSERT(reporter, SkRectIsOnGrid(w, h, r.makeOffset(0, delta), bits) == expected);
+    REPORTER_ASSERT(reporter, SkRectIsOnGrid(w, h, r.makeOffset(0, -delta), bits) == expected);
+
+}
+
+static void test_on_grid(skiatest::Reporter* reporter, int bits, SkScalar cutOff) {
+    const int width = 100;
+    const int height = 100;
+    const SkScalar eps = 0.00001f;
+
+    SkRect r;
+    r.setWH(SkIntToScalar(width), SkIntToScalar(height));
+    REPORTER_ASSERT(reporter, SkRectIsOnGrid(width, height, r, bits));
+
+    test_on_grid(reporter, width, height, r, cutOff - eps, bits, true);
+    test_on_grid(reporter, width, height, r, cutOff + eps, bits, false);
+}
+
+static void test_on_grid(skiatest::Reporter* reporter) {
+    for (int bits = 0; bits <= 8; ++bits) {
+        // The cutoff for being on the grid is  0.5 * (1/grid_size)
+        const SkScalar cutOff = SkScalarInvert(1 << (bits + 1));
+        test_on_grid(reporter, bits, cutOff);
+    }
+}
+
 static const int gWidth = 256;
 static const int gHeight = 256;
 
 static void create(SkBitmap* bm, SkColor color) {
     bm->allocN32Pixels(gWidth, gHeight);
     bm->eraseColor(color);
 }
 
 DEF_TEST(DrawBitmapRect, reporter) {
+    test_on_grid(reporter);
+
     SkBitmap src, dst;
 
     create(&src, 0xFFFFFFFF);
     create(&dst, 0);
 
     SkCanvas canvas(dst);
 
     SkIRect srcR = { gWidth, 0, gWidth + 16, 16 };
     SkRect  dstR = { 0, 0, SkIntToScalar(16), SkIntToScalar(16) };
 
     canvas.drawBitmapRect(src, &srcR, dstR, NULL);
 
     // ensure that we draw nothing if srcR does not intersect the bitmap
     REPORTER_ASSERT(reporter, check_for_all_zeros(dst));
 
     test_nan_antihair();
     test_giantrepeat_crbug118018(reporter);
 
     test_treatAsSprite(reporter);
     test_faulty_pixelref(reporter);
 }