workaround perspective math failures in ImageFilter bounds unit tests

Author: flar

display_list/effects/dl_image_filter.cc

@@ -46,12 +46,21 @@ DlIRect* DlImageFilter::inset_device_bounds(const DlIRect& input_bounds,
                                             DlIRect& output_bounds) {
   if (ctm.IsFinite() && ctm.IsInvertible()) {
     if (ctm.HasPerspective2D()) {
-      DlRect local_bounds = DlRect::Make(input_bounds)
-                                .TransformAndClipBounds(ctm.Invert())
-                                .Expand(-radius_x, -radius_y);
-      output_bounds =
-          DlIRect::RoundOut(local_bounds.TransformAndClipBounds(ctm));
-      return &output_bounds;
+      // Ideally this code would use Impeller classes to do the math, see:
+      // https://github.com/flutter/flutter/issues/159175
+      SkMatrix sk_ctm = ToSkMatrix(ctm);
+      FML_DCHECK(sk_ctm.hasPerspective());
+      SkIRect sk_input_bounds =
+          SkIRect::MakeLTRB(input_bounds.GetLeft(), input_bounds.GetTop(),
+                            input_bounds.GetRight(), input_bounds.GetBottom());
+
+      SkMatrix inverse;
+      if (sk_ctm.invert(&inverse)) {
+        SkRect local_bounds = inverse.mapRect(SkRect::Make(sk_input_bounds));
+        local_bounds.inset(radius_x, radius_y);
+        output_bounds = ToDlIRect(sk_ctm.mapRect(local_bounds).roundOut());
+        return &output_bounds;
+      }
     } else {
       DlVector2 device_radius = map_vectors_affine(ctm, radius_x, radius_y);
       output_bounds =
@@ -70,12 +79,21 @@ DlIRect* DlImageFilter::outset_device_bounds(const DlIRect& input_bounds,
                                              DlIRect& output_bounds) {
   if (ctm.IsFinite() && ctm.IsInvertible()) {
     if (ctm.HasPerspective2D()) {
-      DlRect local_bounds = DlRect::Make(input_bounds)
-                                .TransformAndClipBounds(ctm.Invert())
-                                .Expand(radius_x, radius_y);
-      output_bounds =
-          DlIRect::RoundOut(local_bounds.TransformAndClipBounds(ctm));
-      return &output_bounds;
+      // Ideally this code would use Impeller classes to do the math, see:
+      // https://github.com/flutter/flutter/issues/159175
+      SkMatrix sk_ctm = ToSkMatrix(ctm);
+      FML_DCHECK(sk_ctm.hasPerspective());
+      SkIRect sk_input_bounds =
+          SkIRect::MakeLTRB(input_bounds.GetLeft(), input_bounds.GetTop(),
+                            input_bounds.GetRight(), input_bounds.GetBottom());
+
+      SkMatrix inverse;
+      if (sk_ctm.invert(&inverse)) {
+        SkRect local_bounds = inverse.mapRect(SkRect::Make(sk_input_bounds));
+        local_bounds.outset(radius_x, radius_y);
+        output_bounds = ToDlIRect(sk_ctm.mapRect(local_bounds).roundOut());
+        return &output_bounds;
+      }
     } else {
       DlVector2 device_radius = map_vectors_affine(ctm, radius_x, radius_y);
       output_bounds =

display_list/effects/dl_image_filter_unittests.cc

@@ -156,29 +156,15 @@ static void TestBounds(const DlImageFilter& filter,
         ASSERT_FALSE(matrix.HasPerspective2D()) << matrix;
         TestBoundsWithMatrix(filter, matrix, sourceBounds,
                              expectedLocalOutputQuad);
+        matrix.m[3] = 0.001f;
+        matrix.m[7] = 0.001f;
+        ASSERT_TRUE(matrix.IsInvertible()) << matrix;
+        ASSERT_TRUE(matrix.HasPerspective2D()) << matrix;
+        TestBoundsWithMatrix(filter, matrix, sourceBounds,
+                             expectedLocalOutputQuad);
       }
     }
   }
-
-  {
-    // Just test once with a reasonable perspective transform. Combining
-    // perspective with all of the abusively scaled and skewed transforms
-    // created in the loop above tends to lead to coordinates growing out
-    // of any reasonable scale.
-    DlMatrix matrix;
-    matrix = matrix.Scale({2.0f, 2.0f, 1});
-    matrix = matrix.Translate({1000, 1000, 500});
-    // matrix = DlMatrix::MakeSkew(0.125f, 0.125f) * matrix;
-    matrix = DlMatrix::MakeRotationX(DlDegrees(5)) * matrix;
-    // matrix = DlMatrix::MakeRotationY(DlDegrees(5)) * matrix;
-    // matrix = DlMatrix::MakeTranslation({0, 0, 5});
-    matrix = DlMatrix::MakePerspective(DlDegrees(60), 0.5, -500, 1000) * matrix;
-    // matrix = DlMatrix::MakeLookAt({0, 0, -10}, {0, 0, 10}, {0, 1, 0})
-    // * matrix;
-    ASSERT_TRUE(matrix.IsInvertible()) << matrix;
-    ASSERT_TRUE(matrix.HasPerspective2D()) << matrix;
-    TestBoundsWithMatrix(filter, matrix, sourceBounds, expectedLocalOutputQuad);
-  }
 }
 
 static void TestBounds(const DlImageFilter& filter,
@@ -375,7 +361,7 @@ TEST(DisplayListImageFilter, ErodeNotEquals) {
 
 TEST(DisplayListImageFilter, ErodeBounds) {
   DlErodeImageFilter filter = DlErodeImageFilter(5, 10);
-  DlRect input_bounds = DlRect::MakeLTRB(20, 20, 80, 80).Shift(100, 100);
+  DlRect input_bounds = DlRect::MakeLTRB(20, 20, 80, 80);
   DlRect expected_output_bounds = input_bounds.Expand(-5, -10);
   TestBounds(filter, input_bounds, expected_output_bounds);
 }