Add functionality for copying text within form text fields and form combobox text fields

pdf/pdfium/pdfium_engine.cc

Index: pdf/pdfium/pdfium_engine.cc
diff --git a/pdf/pdfium/pdfium_engine.cc b/pdf/pdfium/pdfium_engine.cc
index 37c01618778ebd942421fbab1c4c6f6b8a3affcf..bbff97013890aae12516c396f1f929ab2d0e46c8 100644
--- a/pdf/pdfium/pdfium_engine.cc
+++ b/pdf/pdfium/pdfium_engine.cc
@@ -1624,6 +1624,25 @@ void PDFiumEngine::FitContentsToPrintableAreaIfRequired(
 void PDFiumEngine::SaveSelectedFormForPrint() {
   FORM_ForceToKillFocus(form_);
   client_->FormTextFieldFocusChange(false);
+  SetInFormTextField(false);
+}
+
+void PDFiumEngine::SetFormSelectedText(const FPDF_FORMHANDLE& hHandle,
+                                       const FPDF_PAGE& page) {
+  size_t form_sel_text_len = FORM_GetSelectedText(hHandle, page, nullptr, 0);
+  if (!form_sel_text_len)
+    return;
+
+  base::string16 selected_form_text16;
+  PDFiumAPIStringBufferSizeInBytesAdapter<base::string16> string_adapter(
+      &selected_form_text16, form_sel_text_len, false);
+  string_adapter.Close(FORM_GetSelectedText(
+      hHandle, page, string_adapter.GetData(), form_sel_text_len));
+
+  std::string selected_form_text = UTF16ToUTF8(selected_form_text16);
+  if (!selected_form_text.empty()) {
+    pp::PDF::SetSelectedText(GetPluginInstance(), selected_form_text.c_str());
+  }
 }
 
 void PDFiumEngine::PrintEnd() {
@@ -1720,18 +1739,23 @@ bool PDFiumEngine::OnMouseDown(const pp::MouseInputEvent& event) {
 
     FORM_OnLButtonDown(form_, pages_[page_index]->GetPage(), 0, page_x, page_y);
     if (form_type > FPDF_FORMFIELD_UNKNOWN) {  // returns -1 sometimes...
-      mouse_down_state_.Set(PDFiumPage::NONSELECTABLE_AREA, target);
+      mouse_down_state_.Set(PDFiumPage::FORM_TEXT_AREA, target);

[Lei Zhang, 2017/06/14 07:07:02]

If we click on a form widget that is not a form text area, is this the right
type to set?

[drgage, 2017/06/14 22:53:39]

Probably not - I'll change this so that it only is set to FORM_TEXT_AREA if the
form_type == FPDF_FORMFIELD_TEXTFIELD.

[drgage, 2017/06/14 22:53:39]

Done.

       bool is_valid_control = (form_type == FPDF_FORMFIELD_TEXTFIELD ||
                                form_type == FPDF_FORMFIELD_COMBOBOX);
 #if defined(PDF_ENABLE_XFA)
       is_valid_control |= (form_type == FPDF_FORMFIELD_XFA);
 #endif
       client_->FormTextFieldFocusChange(is_valid_control);
+
+      // TODO (drgage): come back here and figure out what to do with

[Lei Zhang, 2017/06/14 07:07:02]

I think this is actually correct as is in the non-XFA case. BTW, I referred to
the combo box as drop down control.

It looks like Acrobat Reader can copy text from these two types of fields, so we
should as well. We can work on making combo boxes actually work separately. (XFA
will be even more work to figure out. Maybe leave a TODO(bug_62400) here for
XFA?)

[drgage, 2017/06/14 22:53:39]

Done.

+      // is_valid_control
+      SetInFormTextField(is_valid_control);
       return true;  // Return now before we get into the selection code.
     }
   }
 
   client_->FormTextFieldFocusChange(false);
+  SetInFormTextField(false);
 
   if (area != PDFiumPage::TEXT_AREA)
     return true;  // Return true so WebKit doesn't do its own highlighting.
@@ -1807,11 +1831,13 @@ bool PDFiumEngine::OnMouseUp(const pp::MouseInputEvent& event) {
 
       client_->NavigateTo(target.url, disposition);
       client_->FormTextFieldFocusChange(false);
+      SetInFormTextField(false);
       return true;
     }
     if (area == PDFiumPage::DOCLINK_AREA) {
       client_->ScrollToPage(target.page);
       client_->FormTextFieldFocusChange(false);
+      SetInFormTextField(false);
       return true;
     }
   }
@@ -1827,6 +1853,10 @@ bool PDFiumEngine::OnMouseUp(const pp::MouseInputEvent& event) {
     FORM_OnLButtonUp(form_, pages_[page_index]->GetPage(), 0, page_x, page_y);
   }
 
+  if (area == PDFiumPage::FORM_TEXT_AREA) {
+    SetFormSelectedText(form_, pages_[last_page_mouse_down_]->GetPage());
+  }
+
   if (!selecting_)

[Lei Zhang, 2017/06/14 07:07:02]

The existing code like this member variable and SetSelecting() can use some
updated comments to better explain what they select.

[drgage, 2017/06/14 22:53:40]

Done. Do you think it's sufficient to add an explanation for these in
pdfium_engine.h? I can also add a comment here, but I can make it clear that
selection_ is used for text selection.

     return false;
 
@@ -1991,6 +2021,12 @@ bool PDFiumEngine::OnKeyUp(const pp::KeyboardInputEvent& event) {
   if (last_page_mouse_down_ == -1)
     return false;
 
+  if (in_form_text_field_) {
+    uint32_t modifiers = event.GetModifiers();
+    if (modifiers & PP_INPUTEVENT_MODIFIER_SHIFTKEY)

[Lei Zhang, 2017/06/14 07:07:02]

I tried this code out and noticed if I:
1) used the shift + arrow keys to select some text
2) stopped holding shift
3) used the arrow keys to move around

Then the selection disappears visually, but remains as far as the selection code
for copying is concerned.

[drgage, 2017/06/14 22:53:39]

I see what you mean. I hadn't tried this combination of actions. The same thing
happens if you press any other key, like if you type another letter and erase
what was there, the old selected text is still available for copying just
because the shift key was released. The same thing also happens with the mouse
selection. If you have something selected with the mouse, then press a key, the
visual selection disappears but you can still copy the old selected text.

I can look into how the visual selection code works and try to fix this. 

As far as text selection (i.e. via the selection_ vector for
PDFiumPage::TEXT_AREA text) is concerned, you can't select using the shift and
arrow keys at all, and if you select with the mouse and then press the arrow
keys, the current selection doesn't visually change/disappear, so this isn't a
problem there. I'm thinking another option for handling this bug would be to
mimic this behavior and prevent the visual selection from changing if you press
a key within a form text field when you have text selected, but I don't think
this is a great choice for user experience, so I'm going to look into how the
visual selection code works.

[Lei Zhang, 2017/06/15 18:11:28]

I don't think you need to actually know how the visual selection works. Just
look at how pp::PDF::SetSelectedText() gets called when there is a non-form text
selection, and one does a mouse click to clear that selection.

[drgage, 2017/06/16 02:12:36]

Done.

+      SetFormSelectedText(form_, pages_[last_page_mouse_down_]->GetPage());
+  }
+
   return !!FORM_OnKeyUp(form_, pages_[last_page_mouse_down_]->GetPage(),
                         event.GetKeyCode(), event.GetModifiers());
 }
@@ -3552,6 +3588,10 @@ void PDFiumEngine::SetSelecting(bool selecting) {
     client_->IsSelectingChanged(selecting);
 }
 
+void PDFiumEngine::SetInFormTextField(bool in_form_text_field) {
+  in_form_text_field_ = in_form_text_field;
+}
+
 void PDFiumEngine::ScheduleTouchTimer(const pp::TouchInputEvent& evt) {
   touch_timers_[++next_touch_timer_id_] = evt;
   client_->ScheduleTouchTimerCallback(next_touch_timer_id_,