205006 - scrollSelectionIntoView off by one line when selection starts at beginning of a line

Status: RESOLVED WONTFIX

(Core :: DOM: Core & HTML, defect)

Description

[Christian Schmidt]

While I was working on a patch for bug 104383 I was told to use the following to
scroll the current selection into view:

getBrowser().docShell
  .QueryInterface(Components.interfaces.nsIInterfaceRequestor)
  .getInterface(Components.interfaces.nsISelectionDisplay)
  .QueryInterface(Components.interfaces.nsISelectionController)
  .scrollSelectionIntoView(
      Components.interfaces.nsISelectionController.SELECTION_NORMAL,
      Components.interfaces.nsISelectionController.SELECTION_ANCHOR_REGION,
      true);

However, this fails when the selection starts at the beginning of a line.
Instead the end of the previous line is scrolled into view. If the previous line
longer than the current window size, horizontal scrolling will occur.

I am using Mozilla 1.4b on WinXP.

Comment 1

[Christian Schmidt]

Attachment: Testcase: XUL page

This testcase displays a document that contains a number of lines.

Steps to reproduce:
1. Load test case
2. Select the first word on line 91, e.g. using the mouse
3. Scroll the document to the beginning without clearing the selection
4. Observe that the end of the previous line is scrolled into view, not 
   the selected word
5. An alert box shows the selection. Make sure that the selection does not
   include anything else than the first word, i.e. no linefeeds etc.

Expected results:
When the button is pressed the selected word should be visible.

Comment 2

[rbs]

The real issue was that the selection start's offset (cursor/caret) is logically
after the "\n" at the end of the previous line.

It was discovered that the intended effect of moving the selection to the next
line can be achieved by setting the interline hint ("hintright").
Specicifically, bug 104383 is no using 
+  selection.QueryInterface(Components.interfaces.nsISelectionPrivate)
+    .interlinePosition = true;	

which boils down to nsIFrameSelection::SetHint(HINTRIGHT) which has helped to
achieve the desired effect.

Marking WONTFIX since no further action is required.