[tbb-commits] [tor-browser] 193/311: Bug 1757443 - Correctly account for padding in ResizeObserver content-box size for scrollable frames. r=boris, layout-reviewers a=dmeehan

Tue Apr 26 15:29:53 UTC 2022

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pierov pushed a commit to branch geckoview-99.0.1-11.0-1
in repository tor-browser.

commit a52a423779f78ce3be6965f21588e82309e6746c
Author: Emilio Cobos Álvarez <emilio at crisal.io>
AuthorDate: Fri Mar 18 02:20:01 2022 +0000

    Bug 1757443 - Correctly account for padding in ResizeObserver content-box size for scrollable frames. r=boris,layout-reviewers a=dmeehan
    
    See test.
    
    Differential Revision: https://phabricator.services.mozilla.com/D141398
---
 dom/base/ResizeObserver.cpp                        | 10 +++++-
 .../tests/resize-observer/scrollbars-2.html        | 36 ++++++++++++++++++++++
 2 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/dom/base/ResizeObserver.cpp b/dom/base/ResizeObserver.cpp
index 0b7bf9afe5cd0..8b0b84e706dec 100644
--- a/dom/base/ResizeObserver.cpp
+++ b/dom/base/ResizeObserver.cpp
@@ -49,7 +49,15 @@ static uint32_t GetNodeDepth(nsINode* aNode) {
 static nsSize GetContentRectSize(const nsIFrame& aFrame) {
   if (const nsIScrollableFrame* f = do_QueryFrame(&aFrame)) {
     // We return the scrollport rect for compat with other UAs, see bug 1733042.
-    return f->GetScrollPortRect().Size();
+    // But the scrollPort includes padding (but not border!), so remove it.
+    nsRect scrollPort = f->GetScrollPortRect();
+    nsMargin padding =
+        aFrame.GetUsedPadding().ApplySkipSides(aFrame.GetSkipSides());
+    scrollPort.Deflate(padding);
+    MOZ_ASSERT(!aFrame.PresContext()->UseOverlayScrollbars() ||
+               scrollPort.Size() ==
+                   aFrame.GetContentRectRelativeToSelf().Size());
+    return scrollPort.Size();
   }
   return aFrame.GetContentRectRelativeToSelf().Size();
 }
diff --git a/testing/web-platform/tests/resize-observer/scrollbars-2.html b/testing/web-platform/tests/resize-observer/scrollbars-2.html
new file mode 100644
index 0000000000000..51b470c8a2d61
--- /dev/null
+++ b/testing/web-platform/tests/resize-observer/scrollbars-2.html
@@ -0,0 +1,36 @@
+<!DOCTYPE html>
+<title>ResizeObserver content-box size and scrollbars</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1733042">
+<style>
+  #scrollContainer {
+    width: 100px;
+    height: 100px;
+    /* Should be bigger than any reasonable scrollbar */
+    padding: 30px;
+    border: 10px solid blue;
+    overflow: scroll;
+    background: #818182;
+  }
+
+</style>
+<div id="scrollContainer"></div>
+<script>
+  promise_test(async function() {
+    let count = 0;
+
+    const scrollContainer = document.getElementById('scrollContainer');
+    // 20 to account for the border.
+    const scrollbarSize = scrollContainer.offsetWidth - scrollContainer.clientWidth - 20;
+    let size = await new Promise(resolve => {
+      const observer = new ResizeObserver(entries => {
+        resolve(entries[0].contentBoxSize[0]);
+      });
+      observer.observe(scrollContainer);
+    });
+
+    assert_equals(size.inlineSize, 100 - scrollbarSize);
+    assert_equals(size.blockSize, 100 - scrollbarSize);
+  });
+</script>

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