[Autofill/Autocomplete Feature] Substring matching instead of prefix matching.

components/autofill/content/renderer/form_autofill_util.cc

Index: components/autofill/content/renderer/form_autofill_util.cc
diff --git a/components/autofill/content/renderer/form_autofill_util.cc b/components/autofill/content/renderer/form_autofill_util.cc
index 51a2251258b73d0faf6bf61afbc8fec36b951d11..20a3736f3039a9d1f9bd5ee86d685fc82748c087 100644
--- a/components/autofill/content/renderer/form_autofill_util.cc
+++ b/components/autofill/content/renderer/form_autofill_util.cc
@@ -16,6 +16,7 @@
 #include "components/autofill/core/common/autofill_data_validation.h"
 #include "components/autofill/core/common/autofill_regexes.h"
 #include "components/autofill/core/common/autofill_switches.h"
+#include "components/autofill/core/common/autofill_util.h"
 #include "components/autofill/core/common/form_data.h"
 #include "components/autofill/core/common/form_field_data.h"
 #include "third_party/WebKit/public/platform/WebString.h"
@@ -871,9 +872,7 @@ void PreviewFormField(const FormFieldData& data,
   if (is_initiating_node &&
       (IsTextInput(input_element) || IsTextAreaElement(*field))) {
     // Select the part of the text that the user didn't type.
-    int start = field->value().length();
-    int end = field->suggestedValue().length();
-    field->setSelectionRange(start, end);
+    PreviewSuggestion(field->suggestedValue(), field->value(), field);
   }
 }
 
@@ -1534,4 +1533,15 @@ gfx::RectF GetScaledBoundingBox(float scale, WebElement* element) {
                     bounding_box.height() * scale);
 }
 
+void PreviewSuggestion(const base::string16& suggestion,
+                       const base::string16& user_input,
+                       blink::WebFormControlElement* input_element) {
+  input_element->setSelectionRange(
+      IsFeatureSubstringMatchEnabled()
+          ? std::min(autofill::GetTextSelectionStart(suggestion, user_input),

[please use gerrit instead, 2015/07/03 02:05:43]

GetTextSelectionStart() returns only one thing that's larger than
suggestion.length(): std::string::npos. If you've encountered this, it indicates
a bug. Please fix the bug in GetTextSelectionStart() instead of handling it here
with std::min().

[Pritam Nikam, 2015/07/03 16:21:27]

For password forms we autocomplete field_contents as user punches in text with
the suggestion text. Same goes with password form load completes, username and
password fields get autocomplete by MFU suggestion. 

In suggestions hover case, |GetTextSelectionStart()| returns |std::string::npos|
when |field_contents| varies from |field_suggestion| text.

something like below:

On page load:
username_element->setValue(...);
username_element->setSuggestedValue(...);
input_element->setSelectionRange(suggestedValue, value);


and for suggestion hover:
username_element->setSuggestedValue(...);
input_element->setSelectionRange(value.length(), suggestedValue.length());

i.e. older |value| compared to new |suggestedValue| and that may not be matching
(substring/prefix).

In such cases |setSelectionRange()| with first parameter |std::string::npos|
always set it to "0". If we keep a maximum value cap to
|suggestedValue.length()| then it will position cursor it to end of the
suggestion text.

If we change |GetTextSelectionStart()| to return different value than
|std::string::npos|, we may not be able to identify non-matching case.

For IsFeatureSubstringMatchEnabled() off case, say if new
|suggestedValue.length()| is greater than that of older one, on hover show text
selection from |older_suggestedValue.length() - new_suggestedValue.length()|.

Hope I gave proper explanation. Please let me know if it sounds confusion.

[please use gerrit instead, 2015/07/03 22:05:47]

Now it makes sense. Please put a sentence about this use case in the function
comment for GetTextSelectionStart().

However, this code now changes the behavior of preview-on-hover feature.
Currently it selects the whole text from 0 to suggestion.length(). Your code is
changing the behavior to select from suggestion.length() to suggestion.length().
Do something like this instead please:


-------------------------------------------------------------------
size_t selection_start = IsFeatureSubstringMatchEnabled()
    ? autofill::GetTextSelectionStart(suggestion, user_input)
    : user_input.length();
input_element->setSelectionRange(
    selection_start == std::string16::npos ? 0 : user_input.length(),
    suggestion.length());
-------------------------------------------------------------------


This code is a little bit confusing, however. It would be great if you could
come up with something better.

[Pritam Nikam, 2015/07/06 15:29:27]

Done.


Changed to:

-- [snap] --

  size_t selection_start = user_input.length();
  if (IsFeatureSubstringMatchEnabled()) {
    size_t offset = autofill::GetTextSelectionStart(suggestion, user_input);
    selection_start = (offset == base::string16::npos) ? 0 : offset;
  }

  input_element->setSelectionRange(selection_start, suggestion.length());

-- [snap] --

+                     suggestion.length())
+          : user_input.length(),
+      suggestion.length());
+}
+
 }  // namespace autofill