Improve computeMatrices singular matrix handling.

The existing singular matrix detection in computeMatrices is sufficient
but not necessary. Since compute matrices is already doing a QR
decomposition, use that to determine singularity instead. This is both
faster and more accurate than the previous method for the common case.

BUG=https://bugzilla.mozilla.org/show_bug.cgi?id=1305085

Change-Id: Iccef8368527b45e4eb565eddbebbbcf41ca66a2c
Reviewed-on: https://skia-review.googlesource.com/20054
Reviewed-by: Lee Salzman <lsalzman@mozilla.com>
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>

1 files changed, 38 insertions, 0 deletions

diff --git a/tests/DrawTextTest.cpp b/tests/DrawTextTest.cpp
index 2f8fe056eb..0134d0585d 100644
--- a/tests/DrawTextTest.cpp
+++ b/tests/DrawTextTest.cpp
@@ -128,3 +128,41 @@ DEF_TEST(DrawText_weirdCoordinates, r) {
         canvas->drawString("a", 0.0f, -y, SkPaint());
     }
 }
+
+// Test drawing text with some unusual matricies.
+// We measure success by not crashing or asserting.
+DEF_TEST(DrawText_weirdMatricies, r) {
+    auto surface = SkSurface::MakeRasterN32Premul(100,100);
+    auto canvas = surface->getCanvas();
+
+    SkPaint paint;
+    paint.setAntiAlias(true);
+    paint.setLCDRenderText(true);
+
+    struct {
+        SkScalar textSize;
+        SkScalar matrix[9];
+    } testCases[] = {
+        // 2x2 singular
+        {10, { 0,  0,  0,  0,  0,  0,  0,  0,  1}},
+        {10, { 0,  0,  0,  0,  1,  0,  0,  0,  1}},
+        {10, { 0,  0,  0,  1,  0,  0,  0,  0,  1}},
+        {10, { 0,  0,  0,  1,  1,  0,  0,  0,  1}},
+        {10, { 0,  1,  0,  0,  1,  0,  0,  0,  1}},
+        {10, { 1,  0,  0,  0,  0,  0,  0,  0,  1}},
+        {10, { 1,  0,  0,  1,  0,  0,  0,  0,  1}},
+        {10, { 1,  1,  0,  0,  0,  0,  0,  0,  1}},
+        {10, { 1,  1,  0,  1,  1,  0,  0,  0,  1}},
+        // See https://bugzilla.mozilla.org/show_bug.cgi?id=1305085 .
+        { 1, {10, 20,  0, 20, 40,  0,  0,  0,  1}},
+    };
+
+    for (const auto& testCase : testCases) {
+        paint.setTextSize(testCase.textSize);
+        const SkScalar(&m)[9] = testCase.matrix;
+        SkMatrix mat;
+        mat.setAll(m[0], m[1], m[2], m[3], m[4], m[5], m[6], m[7], m[8]);
+        canvas->setMatrix(mat);
+        canvas->drawString("Hamburgefons", 10, 10, paint);
+    }
+}