Bug 1901464 part 3: Implement ITextProvider::GetVisibleRanges. r=nlapre

Differential Revision: https://phabricator.services.mozilla.com/D236090

Author: jcsteh

accessible/base/TextLeafRange.cpp

@@ -2240,6 +2240,26 @@ void TextLeafRange::ScrollIntoView(uint32_t aScrollType) const {
                                  aScrollType);
 }
 
+nsTArray<TextLeafRange> TextLeafRange::VisibleLines(
+    Accessible* aContainer) const {
+  MOZ_ASSERT(aContainer);
+  // We want to restrict our lines to those visible within aContainer.
+  LayoutDeviceIntRect containerBounds = aContainer->Bounds();
+  nsTArray<TextLeafRange> lines;
+  WalkLineRects([&lines, &containerBounds](TextLeafRange aLine,
+                                           LayoutDeviceIntRect aLineRect) {
+    // XXX This doesn't correctly handle lines that are scrolled out where the
+    // scroll container is a descendant of aContainer. Such lines might
+    // intersect with containerBounds, but the scroll container could be a
+    // descendant of aContainer and should thus exclude this line. See bug
+    // 1945010 for more details.
+    if (aLineRect.Intersects(containerBounds)) {
+      lines.AppendElement(aLine);
+    }
+  });
+  return lines;
+}
+
 bool TextLeafRange::WalkLineRects(LineRectCallback aCallback) const {
   if (mEnd <= mStart) {
     return false;

accessible/base/TextLeafRange.h

@@ -329,6 +329,12 @@ class TextLeafRange final {
 
   MOZ_CAN_RUN_SCRIPT void ScrollIntoView(uint32_t aScrollType) const;
 
+  /**
+   * Returns sub-ranges for all the lines in this range visible within the given
+   * container Accessible.
+   */
+  nsTArray<TextLeafRange> VisibleLines(Accessible* aContainer) const;
+
  private:
   TextLeafPoint mStart;
   TextLeafPoint mEnd;

accessible/tests/browser/windows/uia/browser_textPatterns.js

@@ -2209,3 +2209,82 @@ addUiaTask(
   },
   { uiaEnabled: true, uiaDisabled: true }
 );
+
+/**
+ * Test the Text pattern's GetVisibleRanges method.
+ */
+addUiaTask(
+  `
+<div id="div">
+  <p>line1</p>
+  <p>line2</p>
+  <p style="position: absolute; left: -10000px; width: 1px;">line3</p>
+  <p>line4</p>
+</div>
+<!-- We use 0.5lh so the second line is definitely fully scrolled out.
+     With 1lh, it could be partially visible and thus included. -->
+<textarea id="textarea" style="height: 0.5lh;">line5
+line6
+line7</textarea>
+<hr aria-hidden="true" style="height: 100vh;">
+<p>line8</p>
+  `,
+  async function testTextGetVisibleRanges() {
+    await runPython(`
+      global doc, docText, ranges
+      doc = getDocUia()
+      docText = getUiaPattern(doc, "Text")
+      ranges = docText.GetVisibleRanges()
+    `);
+    // XXX This should be 4 once we fix the scrolling case below.
+    is(
+      await runPython(`ranges.Length`),
+      6,
+      "doc has correct number of visible ranges"
+    );
+    is(
+      await runPython(`ranges.GetElement(0).GetText(-1)`),
+      "line1",
+      "range 0 text correct"
+    );
+    is(
+      await runPython(`ranges.GetElement(1).GetText(-1)`),
+      "line2",
+      "range 1 text correct"
+    );
+    // line3 is off-screen and thus not visible.
+    is(
+      await runPython(`ranges.GetElement(2).GetText(-1)`),
+      "line4",
+      "range 2 text correct"
+    );
+    is(
+      await runPython(`ranges.GetElement(3).GetText(-1)`),
+      "line5\n",
+      "range 3 text correct"
+    );
+    // XXX line6 and line7 are scrolled off screen by the textarea, but we
+    // incorrectly return them for now (ranges 4 and 5).
+    // line8 is scrolled off screen by the document.
+
+    await runPython(`
+      textarea = findUiaByDomId(doc, "textarea")
+      textareaText = getUiaPattern(textarea, "Text")
+      global ranges
+      ranges = textareaText.GetVisibleRanges()
+    `);
+    is(
+      await runPython(`ranges.Length`),
+      1,
+      "textarea has correct number of visible ranges"
+    );
+    is(
+      await runPython(`ranges.GetElement(0).GetText(-1)`),
+      "line5\n",
+      "range 0 text correct"
+    );
+    // line6 and line7 are scrolled off screen by the textarea.
+  },
+  // The IA2 -> UIA proxy doesn't support GetVisibleRanges.
+  { uiaEnabled: true, uiaDisabled: false }
+);

accessible/windows/uia/UiaText.cpp

@@ -66,7 +66,21 @@ UiaText::GetSelection(__RPC__deref_out_opt SAFEARRAY** aRetVal) {
 
 STDMETHODIMP
 UiaText::GetVisibleRanges(__RPC__deref_out_opt SAFEARRAY** aRetVal) {
-  return E_NOTIMPL;
+  if (!aRetVal) {
+    return E_INVALIDARG;
+  }
+  Accessible* acc = Acc();
+  if (!acc) {
+    return CO_E_OBJNOTCONNECTED;
+  }
+  TextLeafRange fullRange = TextLeafRange::FromAccessible(acc);
+  // The most pragmatic way to determine visible text is to walk by line.
+  // XXX TextLeafRange::VisibleLines doesn't correctly handle lines that are
+  // scrolled out where the scroll container is a descendant of acc. See bug
+  // 1945010.
+  nsTArray<TextLeafRange> ranges = fullRange.VisibleLines(acc);
+  *aRetVal = TextLeafRangesToUiaRanges(ranges);
+  return S_OK;
 }
 
 STDMETHODIMP