From d23274a2ed52c83e2af9e52a0d9b36d4a47e460a Mon Sep 17 00:00:00 2001
From: Mats Palmgren <mats@mozilla.com>
Date: Mon, 25 Feb 2019 22:16:57 +0100
Subject: [PATCH] Bug 1529036 - Clip <button> to its border area for event hit
 testing, but not its children.  r=emilio

---
 layout/forms/nsHTMLButtonControlFrame.cpp | 23 ++++---
 layout/forms/test/mochitest.ini           |  1 +
 layout/forms/test/test_bug1529036.html    | 73 +++++++++++++++++++++++
 3 files changed, 85 insertions(+), 12 deletions(-)
 create mode 100644 layout/forms/test/test_bug1529036.html
diff --git a/layout/forms/nsHTMLButtonControlFrame.cpp b/layout/forms/nsHTMLButtonControlFrame.cpp
index 31cfd063924f..f85e469d463a 100644
--- a/layout/forms/nsHTMLButtonControlFrame.cpp
+++ b/layout/forms/nsHTMLButtonControlFrame.cpp
@@ -79,20 +79,19 @@ bool nsHTMLButtonControlFrame::ShouldClipPaintingToBorderBox() {
 
 void nsHTMLButtonControlFrame::BuildDisplayList(
     nsDisplayListBuilder* aBuilder, const nsDisplayListSet& aLists) {
-  // Clip to our border area for event hit testing.
-  Maybe<DisplayListClipState::AutoSaveRestore> eventClipState;
-  const bool isForEventDelivery = aBuilder->IsForEventDelivery();
-  if (isForEventDelivery) {
-    eventClipState.emplace(aBuilder);
-    nsRect rect(aBuilder->ToReferenceFrame(this), GetSize());
-    nscoord radii[8];
-    bool hasRadii = GetBorderRadii(radii);
-    eventClipState->ClipContainingBlockDescendants(rect,
-                                                   hasRadii ? radii : nullptr);
-  }
-
   nsDisplayList onTop;
   if (IsVisibleForPainting()) {
+    // Clip the button itself to its border area for event hit testing.
+    Maybe<DisplayListClipState::AutoSaveRestore> eventClipState;
+    if (aBuilder->IsForEventDelivery()) {
+      eventClipState.emplace(aBuilder);
+      nsRect rect(aBuilder->ToReferenceFrame(this), GetSize());
+      nscoord radii[8];
+      bool hasRadii = GetBorderRadii(radii);
+      eventClipState->ClipContainingBlockDescendants(rect,
+          hasRadii ? radii : nullptr);
+    }
+
     mRenderer.DisplayButton(aBuilder, aLists.BorderBackground(), &onTop);
   }
 
diff --git a/layout/forms/test/mochitest.ini b/layout/forms/test/mochitest.ini
index 22fb071676a7..db1ba3b275e7 100644
--- a/layout/forms/test/mochitest.ini
+++ b/layout/forms/test/mochitest.ini
@@ -65,5 +65,6 @@ skip-if = e10s || toolkit == 'android' # Bug 1170129 - vertical <select> popup n
 [test_textarea_resize.html]
 skip-if = toolkit == 'android'
 [test_bug1327129.html]
+[test_bug1529036.html]
 [test_readonly.html]
 [test_select_key_navigation_bug1498769.html]
diff --git a/layout/forms/test/test_bug1529036.html b/layout/forms/test/test_bug1529036.html
new file mode 100644
index 000000000000..1b1bc297230f
--- /dev/null
+++ b/layout/forms/test/test_bug1529036.html
@@ -0,0 +1,73 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=1529036
+-->
+<head>
+  <meta charset="utf-8">
+  <title>Test for Bug 1529036</title>
+  <script type="application/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="application/javascript" src="/tests/SimpleTest/EventUtils.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+  <style>
+html,body {
+  color:black; background-color:white; font:16px/1 monospace; padding:0; margin:0;
+}
+  </style>
+  <script type="application/javascript">
+
+  /** Test for Bug 1529036 **/
+
+  function doTest() {
+    SimpleTest.waitForExplicitFinish();
+
+    var clicks = 0;
+    var elms = document.querySelectorAll('.click');
+    for (var i = 0; i < elms.length; ++i) {
+      var e = elms[i];
+      e.addEventListener('click', function(event) {
+        ++clicks;
+      });
+    }
+
+    var elms = document.querySelectorAll('.click.hit');
+    for (var i = 0; i < elms.length; ++i) {
+      var e = elms[i];
+      let r = e.getBoundingClientRect();
+      synthesizeMouse(e, 50, 50, {});
+    }
+    is(clicks, elms.length, "click events on overflow");
+
+    clicks = 0;
+    elms = document.querySelectorAll('.click.nohit');
+    for (var i = 0; i < elms.length; ++i) {
+      var e = elms[i];
+      let r = e.getBoundingClientRect();
+      synthesizeMouse(e, 50, 50, {});
+    }
+    is(clicks, 0, "click events on clipped overflow");
+
+    SimpleTest.finish();
+  }
+  </script>
+</head>
+<body onload="SimpleTest.waitForFocus(doTest, window)">
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1529036">Mozilla Bug 1529036</a>
+<p id="display"></p>
+<div id="content" style="display: none">
+
+</div>
+<pre id="test">
+</pre>
+
+<div style="border: 1px solid">
+<button class="click hit" id="t1" style="width:10px; height:10px; padding:20px; border-radius:50%"><div>button<br>button<br>button<br>button<br>button<br></div></button>
+<button class="click hit" id="t2" style="width:10px; height:10px; padding:20px; border:1px solid"><div>button<br>button<br>button<br>button<br>button<br></div></button>
+<button class="click hit" id="t3" style="width:10px; height:10px; border-width:20px; border-radius:50%"><div>button<br>button<br>button<br>button<br>button<br></div></button>
+<button class="click hit" id="t4" style="width:10px; height:10px; border:20px solid"><div>button<br>button<br>button<br>button<br>button<br></div></button>
+<button class="click nohit" id="t5" style="width:10px; height:10px; padding:20px; overflow:hidden; border-radius:50%"><div>button<br>button<br>button<br>button<br>button<br></div></button>
+<button class="click nohit" id="t6" style="width:10px; height:10px; padding:20px; overflow:hidden; border:1px solid"><div>button<br>button<br>button<br>button<br>button<br></div></button>
+</div>
+
+</body>
+</html>
