[PDF Ink Signatures] Implement PdfViewWebPlugin::VisiblePageIndexFromPoint()

Implement this method by checking PDFiumEngine page contents rects to
find the one that contains the given point.

Bug: 335524380
Change-Id: Ic569cfbc13c5bd3f222c4873fb756fc68576ede0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5542804
Reviewed-by: Alan Screen <awscreen@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#1302331}

pdf/pdf_engine.h

@@ -381,6 +381,8 @@ class PDFEngine {
       const std::string& destination) = 0;
   // Gets the index of the most visible page, or -1 if none are visible.
   virtual int GetMostVisiblePage() = 0;
+  // Returns whether the page at `index` is visible or not.
+  virtual bool IsPageVisible(int index) const = 0;
   // Gets the rectangle of the page not including the shadow.
   virtual gfx::Rect GetPageBoundsRect(int index) = 0;
   // Gets the rectangle of the page excluding any additional areas.

pdf/pdf_view_web_plugin.cc

@@ -1971,7 +1971,17 @@ SkBitmap PdfViewWebPlugin::GetImageForOcr(int32_t page_index,
 }
 
 int PdfViewWebPlugin::VisiblePageIndexFromPoint(const gfx::PointF& point) {
-  // TODO(crbug.com/335524380): Implement.
+  gfx::Point rounded_point = gfx::ToRoundedPoint(point);
+  for (int i = 0; i < engine_->GetNumberOfPages(); ++i) {
+    if (!engine_->IsPageVisible(i)) {
+      continue;
+    }
+    auto rect = engine_->GetPageContentsRect(i);
+    if (!rect.Contains(rounded_point)) {
+      continue;
+    }
+    return i;
+  }
   return -1;
 }
 

pdf/pdf_view_web_plugin_unittest.cc

@@ -2440,4 +2440,65 @@ TEST_F(PdfViewWebPluginPrintPreviewTest,
   })"));
 }
 
+#if BUILDFLAG(ENABLE_PDF_INK2)
+using PdfViewWebPluginInkTest = PdfViewWebPluginTest;
+
+TEST_F(PdfViewWebPluginInkTest, VisiblePageIndexFromPoint) {
+  ON_CALL(*engine_ptr_, GetPageContentsRect)
+      .WillByDefault([](int page_index) -> gfx::Rect {
+        // Uniform 80x180 page sizes, with a `kVerticalEmptySpace` gap above
+        // every page.
+        constexpr int kVerticalEmptySpace = 20;
+        constexpr int kHeight = 180;
+        int y = kHeight * page_index + kVerticalEmptySpace * (page_index + 1);
+        return gfx::Rect(/*x=*/10, /*y=*/y, /*width=*/80, /*height=*/kHeight);
+      });
+
+  // Top-left corner of screen.
+  constexpr gfx::PointF kScreenTopLeftCorner(0.0f, 0.0f);
+  // Top-left corner of first page.
+  constexpr gfx::PointF kPage0TopLeftCorner(10.0f, 20.0f);
+  // Bottom-right corner of first page.
+  constexpr gfx::PointF kPage0BottomRightCorner(89.0f, 199.0f);
+  // Gap between first and second page.
+  constexpr gfx::PointF kPage0Page1Gap(50.0f, 201.0f);
+  // Top of second page.
+  constexpr gfx::PointF kPage1Top(50.0f, 220.0f);
+  // Middle of last page.
+  constexpr gfx::PointF kPage12Middle(50.0f, 2510.0f);
+  // Bottom of last page.
+  constexpr gfx::PointF kPage12Bottom(60.0f, 2599.0f);
+  // Beyond the last page.
+  constexpr gfx::PointF kPageBelowLast(60.0f, 2700.0f);
+
+  // Start with the first 2 pages visible.
+  ON_CALL(*engine_ptr_, IsPageVisible)
+      .WillByDefault([](int page_index) -> bool {
+        return page_index >= 0 && page_index <= 1;
+      });
+
+  EXPECT_EQ(-1, plugin_->VisiblePageIndexFromPoint(kScreenTopLeftCorner));
+  EXPECT_EQ(0, plugin_->VisiblePageIndexFromPoint(kPage0TopLeftCorner));
+  EXPECT_EQ(0, plugin_->VisiblePageIndexFromPoint(kPage0BottomRightCorner));
+  EXPECT_EQ(-1, plugin_->VisiblePageIndexFromPoint(kPage0Page1Gap));
+  EXPECT_EQ(1, plugin_->VisiblePageIndexFromPoint(kPage1Top));
+  EXPECT_EQ(-1, plugin_->VisiblePageIndexFromPoint(kPage12Middle));
+  EXPECT_EQ(-1, plugin_->VisiblePageIndexFromPoint(kPage12Bottom));
+  EXPECT_EQ(-1, plugin_->VisiblePageIndexFromPoint(kPageBelowLast));
+
+  // Change the visible page to the last page.
+  ON_CALL(*engine_ptr_, IsPageVisible)
+      .WillByDefault([](int page_index) -> bool { return page_index == 12; });
+
+  EXPECT_EQ(-1, plugin_->VisiblePageIndexFromPoint(kScreenTopLeftCorner));
+  EXPECT_EQ(-1, plugin_->VisiblePageIndexFromPoint(kPage0TopLeftCorner));
+  EXPECT_EQ(-1, plugin_->VisiblePageIndexFromPoint(kPage0BottomRightCorner));
+  EXPECT_EQ(-1, plugin_->VisiblePageIndexFromPoint(kPage0Page1Gap));
+  EXPECT_EQ(-1, plugin_->VisiblePageIndexFromPoint(kPage1Top));
+  EXPECT_EQ(12, plugin_->VisiblePageIndexFromPoint(kPage12Middle));
+  EXPECT_EQ(12, plugin_->VisiblePageIndexFromPoint(kPage12Bottom));
+  EXPECT_EQ(-1, plugin_->VisiblePageIndexFromPoint(kPageBelowLast));
+}
+#endif  // BUILDFLAG(ENABLE_PDF_INK2)
+
 }  // namespace chrome_pdf

pdf/pdfium/pdfium_engine.cc

@@ -3029,6 +3029,8 @@ void PDFiumEngine::CalculateVisiblePages() {
 }
 
 bool PDFiumEngine::IsPageVisible(int index) const {
+  // CalculateVisiblePages() must have been called first to populate
+  // `visible_pages_`. Otherwise, this will always return false.
   return base::Contains(visible_pages_, index);
 }
 

pdf/pdfium/pdfium_engine.h

@@ -144,6 +144,7 @@ class PDFiumEngine : public PDFEngine,
   std::optional<PDFEngine::NamedDestination> GetNamedDestination(
       const std::string& destination) override;
   int GetMostVisiblePage() override;
+  bool IsPageVisible(int index) const override;
   gfx::Rect GetPageBoundsRect(int index) override;
   gfx::Rect GetPageContentsRect(int index) override;
   gfx::Rect GetPageScreenRect(int page_index) const override;
@@ -349,10 +350,6 @@ class PDFiumEngine : public PDFEngine,
   // Calculates which pages should be displayed right now.
   void CalculateVisiblePages();
 
-  // Returns true iff the given page index is visible.  CalculateVisiblePages
-  // must have been called first.
-  bool IsPageVisible(int index) const;
-
   // Internal interface that caches the page index requested by PDFium to get
   // scrolled to. The cache is to be be used during the interval the PDF
   // plugin has not finished handling the scroll request.

pdf/test/test_pdfium_engine.h

@@ -82,11 +82,15 @@ class TestPDFiumEngine : public PDFiumEngine {
 
   int GetNumberOfPages() const override;
 
-  // Returns an empty bookmark list.
-  base::Value::List GetBookmarks() override;
+  MOCK_METHOD(bool, IsPageVisible, (int), (const override));
+
+  MOCK_METHOD(gfx::Rect, GetPageContentsRect, (int), (override));
 
   MOCK_METHOD(gfx::Rect, GetPageScreenRect, (int), (const override));
 
+  // Returns an empty bookmark list.
+  base::Value::List GetBookmarks() override;
+
   MOCK_METHOD(void, SetGrayscale, (bool), (override));
 
   uint32_t GetLoadedByteSize() override;