Hippo CanvasText doesn't handle scroll multiline messages properly

[Zack]

If a Chat message is sent that exceeds 1 line, then when the Chat bubbles reach the bottom of the screen, the bottom-most ones will be hidden. It is not possible to scroll down far enough to see what the most recent messages were.

[Simon]

Was stumbling over the same problem - I think there is a problem in hippo.CanvasText when using the hippo.CANVAS_SIZE_WRAP_WORD option with long text that wraps. Lines that wraps are then truncated at the bottom of the canvas. With gtk.TextBuffer this problem does not arise. So I guess it has to be fixed in hippo.canvas.

[Zack]

The 'verified' flag is for verifying that fixes are correct.

Maybe you meant 'Accept ticket' :)

[Simon]

thought it means that I can reproduce the bug - but make sense the other way round :)

[jg]

Unless this is a simple obvious one line fix, we should wait for trial-3.

If it is, put it back in the untriaged state with the patch attached so I'll see it again.

[coderanger]

Adding reporter to CC list

[coderanger]

Adding reporter to CC list

[jg]

Really just doesn't scroll properly.

[morgs]

Changing from CanvasText to gtk.TextView fixes the scrolling, although it messes up the formatting. This suggests the problem is with CanvasText.

[morgs]

Now it is scrolling too much - see #3648 which I will mark as a duplicate of this.

See https://dev.laptop.org/attachment/ticket/3648/3648-morgs.png for a screenshot.

[morgs]

A report of it still not scrolling enough: #3923

[bemasc]

This is still happening; it renders Chat nearly unusable.

[morgs]

Reported again: #4636

[morgs]

Replying to AlbertCahalan:

Every time I get a message, the window scrolls way past the end of the text. It's possible I triggered this by trying to use the arrow keys as I do in xchat. The other person I was chatting with had the problem as well; he solved it by repeatedly leaving and reentering the chat. So with **every** message, I find myself staring at an empty white screen. I have to use the scrollbar to get back up. Then another message comes in, and I'm thrown back to that white screen again.

Reported again: #5054. We need to fix this for Update.1 if at all possible.

[Eben]

So, there are two problems here, both of which need to be fixed to make chat usable.

1. The chat shouldn't, obviously, scroll up and off screen. Instead, it should place the most recent message directly above the input field, one line above, leaving the remaining space for previous messages to give context. Essentially, this means that it should automatically scroll to the bottom of the list with each message (once the "bottom" is properly defined, to rid us of the extra whitespace).

2. The auto-scrolling should only happen when the scroll position of the window was at its maximum before a new message gets added. That is, If I scroll up a few lines to read something, new messages should not reset my scroll position to the bottom, making it impossible for me to catch up on or revisit past conversation. This is a fundamental that a lot of chat clients got wrong for a long long time. Let's not make that mistake.

[morgs]

Replying to Eben:

So, there are two problems here, both of which need to be fixed to make chat usable. 1. The chat shouldn't, obviously, scroll up and off screen. Instead, it should place the most recent message directly above the input field, one line above, leaving the remaining space for previous messages to give context. Essentially, this means that it should automatically scroll to the bottom of the list with each message (once the "bottom" is properly defined, to rid us of the extra whitespace).

This is the problem here, with hippocanvas.

Please can we have this considered for the Update.1 milestone? jg? It makes Chat quite unusable for more than one screenful of chatting. relnoting this issue won't help with usability...

The alternative is very intrusive changes to stop using hippocanvas for the layout - we would have to reimplement CanvasRoundBox in gtk for example.

2. The auto-scrolling should only happen when the scroll position of the window was at its maximum before a new message gets added. That is, If I scroll up a few lines to read something, new messages should not reset my scroll position to the bottom, making it impossible for me to catch up on or revisit past conversation. This is a fundamental that a lot of chat clients got wrong for a long long time. Let's not make that mistake.

Good point. Logged as a new bug, #5160, against Chat.

[morgs]

Please consider this for Update.1.

With no long lines that are wrapped, Chat's scrollbar starts to scroll too far down after a screenful or so. That will be somewhat mitigated with #5160. However the moment you enter a long line of text, it doesn't scroll far enough, meaning you can't see all of the latest message even when scrolled down to the fullest extent.

[humptybump]

FYI - with all of the G1G1 users now pounding on the activities, this one has become a very frequent point. if the children only have short chats with short messages, it will not be as obvious but the adults with the G1G1 XOs are typing a lot.

Please indicate is you need explicit test cases and I'll get them documented.

[jg]

Marco, any chance on this one?

[marco]

It should be fixable, it's matter to find the time to look at it :)

morgs, maybe you can provide me a testcase for this? It would save me some time.

[marco]

So, interaction between gtk scrollbars and the canvas is "interesting".

Looks like you can use hippo.CanvasScrollbars to get this to work correctly (something like the patch I attached).

[morgs]

Thanks for the patch marco, works great.

[morgs]

Works in Joyride 1491.

[morgs]

See #5814 for Update.1 inclusion request

[morgs]

Fixed in Update.1 673.