Bug 1642603 - Make TransformAndClipBounds stop discarding the corner positions...

Bug 1642603 - Make TransformAndClipBounds stop discarding the corner positions of empty rectangles. r=kip, a=RyanVM Differential Revision: https://phabricator.services.mozilla.com/D79582

Bug 1642603 - Make TransformAndClipBounds stop discarding the corner positions...
Bug 1642603 - Make TransformAndClipBounds stop discarding the corner positions of empty rectangles. r=kip, a=RyanVM Differential Revision: https://phabricator.services.mozilla.com/D79582
fd316f0f · Markus Stange · d373847e · fd316f0f · fd316f0f · fd316f0f
Commit fd316f0f authored Jun 17, 2020 by Markus Stange
--- a/gfx/2d/Matrix.cpp
+++ b/gfx/2d/Matrix.cpp
@@ -122,7 +122,7 @@ Span<Point4DTyped<UnknownUnits, F>> IntersectPolygon(
    Span<Point4DTyped<UnknownUnits, F>> aPoints,
    const Point4DTyped<UnknownUnits, F>& aPlaneNormal,
    Span<Point4DTyped<UnknownUnits, F>> aDestBuffer) {
-  if (aPoints.Length() < 3 || aDestBuffer.Length() < 3) {
+  if (aPoints.Length() < 1 || aDestBuffer.Length() < 1) {
    return {};
  }


--- a/gfx/2d/Matrix.h
+++ b/gfx/2d/Matrix.h
@@ -837,10 +837,6 @@ class Matrix4x4Typed {
  size_t TransformAndClipRect(const RectTyped<SourceUnits, F>& aRect,
                              const RectTyped<TargetUnits, F>& aClip,
                              PointTyped<TargetUnits, F>* aVerts) const {
-    if (aRect.IsEmpty() || aClip.IsEmpty()) {
-      return 0;
-    }
-
    typedef Point4DTyped<UnknownUnits, F> P4D;

    // The initial polygon is made up by the corners of aRect in homogenous

--- a/gfx/tests/gtest/TestMatrix.cpp
+++ b/gfx/tests/gtest/TestMatrix.cpp
@@ -57,6 +57,14 @@ TEST(Matrix, TransformAndClipRect)
  EXPECT_TRUE(
      m2.TransformAndClipBounds(Rect(0, 0, 100, 100), Rect(1024, 1024, 0, 0))
          .IsEmpty());
+
+  // Empty rectangles should still have meaningful corners.
+  EXPECT_TRUE(m.TransformAndClipBounds(Rect(150, 50, 0, 200), c)
+                  .IsEqualEdges(Rect(150, 100, 0, 100)));
+  EXPECT_TRUE(m.TransformAndClipBounds(Rect(150, 150, 0, 0), c)
+                  .IsEqualEdges(Rect(150, 150, 0, 0)));
+  EXPECT_TRUE(m.TransformAndClipBounds(Rect(150, 100, 300, 0), c)
+                  .IsEqualEdges(Rect(150, 100, 50, 0)));
 }

 TEST(Matrix4x4Flagged, Mult)

--- a/layout/base/PresShell.h
+++ b/layout/base/PresShell.h
@@ -575,7 +575,8 @@ class PresShell final : public nsStubDocumentObserver,
   * Scrolls the view of the document so that the given area of a frame
   * is visible, if possible. Layout is not flushed before scrolling.
   *
-   * @param aRect relative to aFrame
+   * @param aRect Relative to aFrame. The rect edges will be respected even if
+   * the rect is empty.
   * @param aVertical see ScrollContentIntoView and ScrollAxis
   * @param aHorizontal see ScrollContentIntoView and ScrollAxis
   * @param aScrollFlags if SCROLL_FIRST_ANCESTOR_ONLY is set, only the

--- a/layout/base/nsLayoutUtils.h
+++ b/layout/base/nsLayoutUtils.h
@@ -913,6 +913,8 @@ class nsLayoutUtils {
   * aAncestor. Computes the bounding-box of the true quadrilateral.
   * Pass non-null aPreservesAxisAlignedRectangles and it will be set to true if
   * we only need to use a 2d transform that PreservesAxisAlignedRectangles().
+   * The corner positions of aRect are treated as meaningful even if aRect is
+   * empty.
   *
   * |aMatrixCache| allows for optimizations in recomputing the same matrix over
   * and over. The argument can be one of the following values:

--- a/layout/reftests/bugs/1642603-1-ref.html
+++ b/layout/reftests/bugs/1642603-1-ref.html
+<!DOCTYPE html>
+<html lang="en">
+<meta charset="utf-8">
+<title>Reference: Bug 1642603 - scrollIntoView() should work on empty rects, even inside transforms</title>
+
+<style>
+
+body {
+  margin: 0;
+}
+
+.container {
+  overflow: auto;
+  perspective: 5px;
+  border: 1px solid black;
+  width: 300px;
+  height: 300px;
+}
+
+.absoluteElement {
+  transform: translateX(0);
+}
+
+.spacer {
+  height: 500px;
+}
+
+.zeroSizeBox {
+  margin-left: 30px;
+  width: 0;
+  height: 20px;
+}
+
+</style>
+
+<div class="container">
+  <div class="absoluteElement">
+    <div class="spacer"></div>
+    <p>This text should be visible.</p>
+    <div class="zeroSizeBox"></div>
+  </div>
+</div>
+
+<script>
+document.querySelector('.container').scrollTop = 1000; // scroll to the end
+</script>
--- a/layout/reftests/bugs/1642603-1.html
+++ b/layout/reftests/bugs/1642603-1.html
+<!DOCTYPE html>
+<html lang="en">
+<meta charset="utf-8">
+<title>Bug 1642603 - scrollIntoView() should work on empty rects, even inside transforms</title>
+
+<style>
+
+body {
+  margin: 0;
+}
+
+.container {
+  overflow: auto;
+  perspective: 5px;
+  border: 1px solid black;
+  width: 300px;
+  height: 300px;
+}
+
+.absoluteElement {
+  transform: translateX(0);
+}
+
+.spacer {
+  height: 500px;
+}
+
+.zeroSizeBox {
+  margin-left: 30px;
+  width: 0;
+  height: 20px;
+}
+
+</style>
+
+<div class="container">
+  <div class="absoluteElement">
+    <div class="spacer"></div>
+    <p>This text should be visible.</p>
+    <div class="zeroSizeBox"></div>
+  </div>
+</div>
+
+<script>
+document.querySelector('.container').scrollTop = 0;
+document.querySelector('.zeroSizeBox').scrollIntoView();
+</script>
--- a/layout/reftests/bugs/reftest.list
+++ b/layout/reftests/bugs/reftest.list
@@ -2103,3 +2103,4 @@ fuzzy(0-145,0-48536) == 1614788-1.svg 1614788-1-ref.svg # large fuzz necesary to
 fuzzy-if(OSX,0-42,0-4) fuzzy-if((Android||winWidget)&&!webrender,0-115,0-2) == 1617515-1.html 1617515-1-ref.html
 fuzzy(0-2,0-21184) == 1626259-1.html 1626259-1-ref.html
 fuzzy(0-2,0-21184) == 1626259-2.html 1626259-2-ref.html
+== 1642603-1.html 1642603-1-ref.html