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 a7912a6e344bf60ebe8f3382be9f9620444d0cec..4d7a7beaf82d57fa1f2245ee2dcb9b4adb729e15 100644
--- a/pdf/pdfium/pdfium_page.cc
+++ b/pdf/pdfium/pdfium_page.cc
@@ -271,15 +271,22 @@ 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 = FPDPage_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 +294,15 @@ 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,
+    // 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)