PDF: Use the z-order when there is a link and widget overlaps.

pdf/pdfium/pdfium_page.cc

Index: pdf/pdfium/pdfium_page.cc
diff --git a/pdf/pdfium/pdfium_page.cc b/pdf/pdfium/pdfium_page.cc
index 79410c46987c0e907459cb39ab7452415efbf1db..93e764564f34d57a7f10e8ef9261c62438b2d91b 100644
--- a/pdf/pdfium/pdfium_page.cc
+++ b/pdf/pdfium/pdfium_page.cc
@@ -263,7 +263,8 @@ PDFiumPage::Area PDFiumPage::GetCharIndex(const pp::Point& point,
   if (!available_)
     return NONSELECTABLE_AREA;
   pp::Point point2 = point - rect_.point();
-  double new_x, new_y;
+  double new_x;
+  double new_y;
   FPDF_DeviceToPage(GetPage(), 0, 0, rect_.width(), rect_.height(),
         rotation, point2.x(), point2.y(), &new_x, &new_y);
 
@@ -271,15 +272,22 @@ PDFiumPage::Area PDFiumPage::GetCharIndex(const pp::Point& point,
       GetTextPage(), new_x, new_y, kTolerance, kTolerance);
   *char_index = rv;
 
+  FPDF_LINK link = FPDFLink_GetLinkAtPoint(GetPage(), new_x, new_y);
   int control =
       FPDPage_HasFormFieldAtPoint(engine_->form(), GetPage(), new_x, new_y);
-  if (control > FPDF_FORMFIELD_UNKNOWN) {
-    *form_type = control;
-    return PDFiumPage::NONSELECTABLE_AREA;
-  }
 
-  FPDF_LINK link = FPDFLink_GetLinkAtPoint(GetPage(), new_x, new_y);
-  if (link) {
+  // If there is a control and link at the same point, figure out their z-order
+  // to determine which is on top.
+  if (link && control > FPDF_FORMFIELD_UNKNOWN) {
+    int control_z_order = FPDFPage_FormFieldZOrderAtPoint(
+        engine_->form(), GetPage(), new_x, new_y);
+    int link_z_order = FPDFLink_GetLinkZOrderAtPoint(GetPage(), new_x, new_y);
+    DCHECK_NE(control_z_order, link_z_order);
+    if (control_z_order > link_z_order) {
+      *form_type = control;
+      return PDFiumPage::NONSELECTABLE_AREA;
+    }
+
     // We don't handle all possible link types of the PDF. For example,
     // launch actions, cross-document links, etc.
     // In that case, GetLinkTarget() will return NONSELECTABLE_AREA
@@ -287,6 +295,16 @@ PDFiumPage::Area PDFiumPage::GetCharIndex(const pp::Point& point,
     PDFiumPage::Area area = GetLinkTarget(link, target);
     if (area != PDFiumPage::NONSELECTABLE_AREA)
       return area;
+  } else if (link) {
+    // We don't handle all possible link types of the PDF. For example,
+    // launch actions, cross-document links, etc.
+    // See identical block above.
+    PDFiumPage::Area area = GetLinkTarget(link, target);
+    if (area != PDFiumPage::NONSELECTABLE_AREA)
+      return area;
+  } else if (control > FPDF_FORMFIELD_UNKNOWN) {
+    *form_type = control;
+    return PDFiumPage::NONSELECTABLE_AREA;
   }
 
   if (rv < 0)