[haiku-bugs] [Haiku] #15354: BTextView's _Refresh() results in line counts out of sync

From: "Haiku" <trac@xxxxxxxxxxxx>
To: undisclosed-recipients: ;
Date: Sun, 15 Sep 2019 08:52:58 -0000

#15354: BTextView's _Refresh() results in line counts out of sync
--------------------------------+------------------------------
Reporter:  humdinger           |        Owner:  nobody
     Type:  bug                 |       Status:  new
Priority:  normal              |    Milestone:  Unscheduled
Component:  Kits/Interface Kit  |      Version:  R1/Development
Keywords:                      |   Blocked By:
Blocking:                      |  Has a Patch:  0
Platform:  All                 |
--------------------------------+------------------------------
This is hrev53452.

To see the effect, open an email in Mail, select 3 lines, and press
"Reply".

Each line should get a quote mark "> ". Instead we get a quote mark for
each character, all in the first line. The relevant code is at https://git
.haiku-os.org/haiku/tree/src/apps/mail/MailWindow.cpp#n2270:
{{{
fContentView->TextView()->SetText(text, finish - start);
free(text);

finish = fContentView->TextView()->CountLines();
for (int32 loop = 0; loop < finish; loop++) {
         fContentView->TextView()->GoToLine(loop);
         fContentView->TextView()->Insert((const char*)QUOTE);
}
}}}

The {{{CountLines()}}} and the {{{GoToLine()}}} apparently use the number
of characters, not the number of lines.

Here's PulkoMandy's analysis:

[10:16] <PulkoMandy> apparently BTextView has a cache for the line

offset (fLines array of offsets or something like that), my guess would be
that this somehow gets out of sync when calling SetText in this case?

[10:18] <PulkoMandy> it seems there is a problem, yes

[10:19] <PulkoMandy> setting the text in BTextView eventually calls

_Refresh which is in charge of recomputing everything. The input to this
is offsets (in characters) for the start and end of the range to refresh

[10:20] <PulkoMandy> and it uses _LineAt to convert these to line

offsets. Except it does this before calling _RecalculateLineBreaks, so it
is doing so using the line offsets from the previous state of the text,
before insert was called

And:

[10:25] <PulkoMandy> if my guess is correct, you could maybe workaround

this by calling SetText twice with the same text

[10:25] <PulkoMandy> hopefully the second time it will do the right

thing, and then CountLines will work

That workaround didn't help, though.
--
Ticket URL: <https://dev.haiku-os.org/ticket/15354>
Haiku <https://dev.haiku-os.org>
The Haiku operating system.

[haiku-bugs] [Haiku] #15354: BTextView's _Refresh() results in line counts out of sync

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