Remove PerformClipping(),CanClipSelf() and the related logic in LTHCommon.

There is a precision lost issue for texture layers with CSS
transforms(Scaling) when applying TextureDrawQuad::PerformClipping()
to avoid explicitly setting a scissor. The rect is first divided by
the scale_factor, then round to integer value and finally multiplied
by the scale_factor in GLRenderer::EnqueueTextureQuad(). The round
process loses precision and the later scale operation enlarges the
error. This error leads to wrong width and height drawn and
introduces visual defects. 

BUG=240259

Review URL: https://codereview.chromium.org/24427006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227177 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 0 insertions, 172 deletions

diff --git a/cc/quads/draw_quad_unittest.cc b/cc/quads/draw_quad_unittest.cc
index 08a1a7a..986d3d6 100644
--- a/cc/quads/draw_quad_unittest.cc
+++ b/cc/quads/draw_quad_unittest.cc
@@ -506,102 +506,6 @@ TEST(DrawQuadTest, CopyTextureDrawQuad) {
   EXPECT_EQ(flipped, copy_quad->flipped);
 }
 
-TEST(DrawQuadTest, ClipTextureDrawQuad) {
-  gfx::Rect opaque_rect(3, 7, 10, 12);
-  unsigned resource_id = 82;
-  bool premultiplied_alpha = true;
-  bool flipped = true;
-  CREATE_SHARED_STATE();
-  // The original quad position is (30, 40) its size is 50*60.
-  shared_state->content_to_target_transform =
-      gfx::Transform(1.f, 0.f, 0.f, 1.f, 10.f, 20.f);
-  // After transformation, the quad position is (40, 60) its size is 50*60.
-  shared_state->clip_rect = gfx::Rect(50, 70, 30, 20);
-
-  // The original quad is 'ABCD', the clipped quad is 'abcd':
-  // 40 50       90
-  //  B--:-------C 60
-  //  |  b----c -|-70
-  //  |  |    |  |
-  //  |  a----d -|-90
-  //  |          |
-  //  A----------D 120
-  // UV and vertex opacity are stored per vertex on the parent rectangle 'ABCD'.
-
-  // This is the UV value for vertex 'B'.
-  gfx::PointF uv_top_left(0.1f, 0.2f);
-  // This is the UV value for vertex 'D'.
-  gfx::PointF uv_bottom_right(0.9f, 0.8f);
-  // This the vertex opacity for the vertices 'ABCD'.
-  const float vertex_opacity[] = { 0.3f, 0.4f, 0.7f, 0.8f };
-  {
-    CREATE_QUAD_8_NEW(TextureDrawQuad,
-                      opaque_rect,
-                      resource_id,
-                      premultiplied_alpha,
-                      uv_top_left,
-                      uv_bottom_right,
-                      SK_ColorTRANSPARENT,
-                      vertex_opacity,
-                      flipped);
-    CREATE_QUAD_7_ALL(TextureDrawQuad,
-                      resource_id,
-                      premultiplied_alpha,
-                      uv_top_left,
-                      uv_bottom_right,
-                      SK_ColorTRANSPARENT,
-                      vertex_opacity,
-                      flipped);
-    EXPECT_TRUE(quad_all->PerformClipping());
-
-    // This is the expected UV value for vertex 'b'.
-    // uv(b) = uv(B) + (Bb / BD) * (uv(D) - uv(B))
-    // 0.3 = 0.2 + (10 / 60) * (0.8 - 0.2)
-    gfx::PointF uv_top_left_clipped(0.26f, 0.3f);
-    // This is the expected UV value for vertex 'd'.
-    // uv(d) = uv(B) + (Bd / BD) * (uv(D) - uv(B))
-    gfx::PointF uv_bottom_right_clipped(0.74f, 0.5f);
-    // This the expected vertex opacity for the vertices 'abcd'.
-    // They are computed with a bilinear interpolation of the corner values.
-    const float vertex_opacity_clipped[] = { 0.43f, 0.45f, 0.65f, 0.67f };
-
-    EXPECT_EQ(uv_top_left_clipped, quad_all->uv_top_left);
-    EXPECT_EQ(uv_bottom_right_clipped, quad_all->uv_bottom_right);
-    EXPECT_FLOAT_ARRAY_EQ(vertex_opacity_clipped, quad_all->vertex_opacity, 4);
-  }
-
-  uv_top_left = gfx::PointF(0.8f, 0.7f);
-  uv_bottom_right = gfx::PointF(0.2f, 0.1f);
-  {
-    CREATE_QUAD_8_NEW(TextureDrawQuad,
-                      opaque_rect,
-                      resource_id,
-                      premultiplied_alpha,
-                      uv_top_left,
-                      uv_bottom_right,
-                      SK_ColorTRANSPARENT,
-                      vertex_opacity,
-                      flipped);
-    CREATE_QUAD_7_ALL(TextureDrawQuad,
-                      resource_id,
-                      premultiplied_alpha,
-                      uv_top_left,
-                      uv_bottom_right,
-                      SK_ColorTRANSPARENT,
-                      vertex_opacity,
-                      flipped);
-    EXPECT_TRUE(quad_all->PerformClipping());
-
-    // This is the expected UV value for vertex 'b'.
-    gfx::PointF uv_top_left_clipped(0.68f, 0.6f);
-    // This is the expected UV value for vertex 'd'.
-    gfx::PointF uv_bottom_right_clipped(0.32f, 0.4f);
-
-    EXPECT_EQ(uv_top_left_clipped, quad_all->uv_top_left);
-    EXPECT_EQ(uv_bottom_right_clipped, quad_all->uv_bottom_right);
-  }
-}
-
 TEST(DrawQuadTest, CopyTileDrawQuad) {
   gfx::Rect opaque_rect(33, 44, 22, 33);
   unsigned resource_id = 104;
diff --git a/cc/quads/texture_draw_quad.cc b/cc/quads/texture_draw_quad.cc
index ae7cfd6..191dcc4 100644
--- a/cc/quads/texture_draw_quad.cc
+++ b/cc/quads/texture_draw_quad.cc
@@ -84,80 +84,6 @@ const TextureDrawQuad* TextureDrawQuad::MaterialCast(const DrawQuad* quad) {
   return static_cast<const TextureDrawQuad*>(quad);
 }
 
-bool TextureDrawQuad::PerformClipping() {
-  // This only occurs if the rect is only scaled and translated (and thus still
-  // axis aligned).
-  if (!quadTransform().IsPositiveScaleOrTranslation())
-    return false;
-
-  // Grab our scale and make sure it's positive.
-  float x_scale = static_cast<float>(quadTransform().matrix().getDouble(0, 0));
-  float y_scale = static_cast<float>(quadTransform().matrix().getDouble(1, 1));
-
-  // Grab our offset.
-  gfx::Vector2dF offset(
-      static_cast<float>(quadTransform().matrix().getDouble(0, 3)),
-      static_cast<float>(quadTransform().matrix().getDouble(1, 3)));
-
-  // Transform the rect by the scale and offset.
-  gfx::RectF rect_f = rect;
-  rect_f.Scale(x_scale, y_scale);
-  rect_f += offset;
-
-  // Perform clipping and check to see if the result is empty.
-  gfx::RectF clipped_rect = IntersectRects(rect_f, clipRect());
-  if (clipped_rect.IsEmpty()) {
-    rect = gfx::Rect();
-    uv_top_left = gfx::PointF();
-    uv_bottom_right = gfx::PointF();
-    return true;
-  }
-
-  // Create a new uv-rect by clipping the old one to the new bounds.
-  gfx::Vector2dF uv_scale(uv_bottom_right - uv_top_left);
-  uv_scale.Scale(1.f / rect_f.width(), 1.f / rect_f.height());
-  uv_bottom_right = uv_top_left +
-      gfx::ScaleVector2d(
-          clipped_rect.bottom_right() - rect_f.origin(),
-          uv_scale.x(),
-          uv_scale.y());
-  uv_top_left = uv_top_left +
-      gfx::ScaleVector2d(
-          clipped_rect.origin() - rect_f.origin(),
-          uv_scale.x(),
-          uv_scale.y());
-
-  // Indexing according to the quad vertex generation:
-  // 1--2
-  // |  |
-  // 0--3
-  if (vertex_opacity[0] != vertex_opacity[1]
-      || vertex_opacity[0] != vertex_opacity[2]
-      || vertex_opacity[0] != vertex_opacity[3]) {
-    const float x1 = (clipped_rect.x() - rect_f.x()) / rect_f.width();
-    const float y1 = (clipped_rect.y() - rect_f.y()) / rect_f.height();
-    const float x3 = (clipped_rect.right() - rect_f.x()) / rect_f.width();
-    const float y3 = (clipped_rect.bottom() - rect_f.y()) / rect_f.height();
-    const float x1y1 = x1 * vertex_opacity[2] + (1.0f - x1) * vertex_opacity[1];
-    const float x1y3 = x1 * vertex_opacity[3] + (1.0f - x1) * vertex_opacity[0];
-    const float x3y1 = x3 * vertex_opacity[2] + (1.0f - x3) * vertex_opacity[1];
-    const float x3y3 = x3 * vertex_opacity[3] + (1.0f - x3) * vertex_opacity[0];
-    vertex_opacity[0] = y3 * x1y3 + (1.0f - y3) * x1y1;
-    vertex_opacity[1] = y1 * x1y3 + (1.0f - y1) * x1y1;
-    vertex_opacity[2] = y1 * x3y3 + (1.0f - y1) * x3y1;
-    vertex_opacity[3] = y3 * x3y3 + (1.0f - y3) * x3y1;
-  }
-
-  // Move the clipped rectangle back into its space.
-  clipped_rect -= offset;
-  clipped_rect.Scale(1.0f / x_scale, 1.0f / y_scale);
-  rect = gfx::Rect(static_cast<int>(clipped_rect.x() + 0.5f),
-                   static_cast<int>(clipped_rect.y() + 0.5f),
-                   static_cast<int>(clipped_rect.width() + 0.5f),
-                   static_cast<int>(clipped_rect.height() + 0.5f));
-  return true;
-}
-
 void TextureDrawQuad::ExtendValue(base::DictionaryValue* value) const {
   value->SetInteger("resource_id", resource_id);
   value->SetBoolean("premultiplied_alpha", premultiplied_alpha);
diff --git a/cc/quads/texture_draw_quad.h b/cc/quads/texture_draw_quad.h
index 7f06618..4aa4d7a 100644
--- a/cc/quads/texture_draw_quad.h
+++ b/cc/quads/texture_draw_quad.h
@@ -53,8 +53,6 @@ class CC_EXPORT TextureDrawQuad : public DrawQuad {
 
   static const TextureDrawQuad* MaterialCast(const DrawQuad*);
 
-  bool PerformClipping();
-
  private:
   TextureDrawQuad();
   virtual void ExtendValue(base::DictionaryValue* value) const OVERRIDE;