[scribus-dev] Question about culling area

[Elvis Stansvik]

2011/8/11 Elvis Stansvik <elvstone at gmail.com>:
> Hi Andreas,
>
> 2011/8/11 Andreas Vox <andreas.vox at googlemail.com>:
>> Hi Elvis!
>>
>> I introduced the culling area in order to skip objects when drawing just a
>> rectangle part of the canvas.
>> Culling area = null means no limitation.
>>
>> The culling area is not a clipping area, that's what PoLine is for. Can't
>> you use the PoLine of the cell's
>> textframe for your purposes?
>
> Yes, I realize that I've confused myself a bit.
>
> My confusion comes from thinking that I could somehow paint parts of
> the table (cells) in DrawObj_Item(...). This is obviously not possible
> as the item needs to repaint itself entirely if requested to do so by
> the canvas. Right?
>
> The problem I'm facing now is that on each key press, I'm now doing:
>
> m_table->activeCell().textFrame()->handleModeEditKey(event, repeat);
> m_table->update();
>
> This will trigger a re-paint of the entire canvas, and the resulting
> lag when typing is quite noticable compared to typing in a regular
> text frame.
>
> I shouldn't have to call m_table->update() right? That will trigger a
> lot of things that aren't necessary after a just a key press.
>
> Just something like
>
> m_canvas->update(m_canvas->canvasToLocal(m_table->getBoundingRect()));
>
> should be enough? But for some reason that isn't working; sometimes
> the table DrawObj_Item is called and sometimes it's not :/
>
> Need to do more debugging here.

So, after some investigation, the only way I've found reliably works
to get my table repainted, without resulting in a repaint of the
entire canvas, is:

bool repeat;
m_table->activeCell().textFrame()->handleModeEditKey(event, repeat);
m_canvas->m_viewMode.forceRedraw = true;
m_canvas->update(m_canvas->canvasToLocal(m_table->getBoundingRect()));

This however implies making my CanvasMode_EditTable a friend of Canvas
(to be able to set the forceRedraw). It feels like a hack, but the
same thing is done e.g. by the CanvasMode_Normal when selecting items.
It seems most of the canvas modes have been made friends of Canvas,
for this or other purposes.

Without the forceRedraw, the paintEvent of the Canvas will return
without painting anything, I guess because of some internal buffering
(I even tried with a call to m_canvas->update() without any rectangle
parameter).

Is there any cleaner solution?

Otherwise I will go with this approach for now, since I need to get on
with other things.

When it comes to the optimization of not having to repaint the entire
table on a keystroke, I'll leave that for now. Possibly in the future
the table painter could keep a QCache of QImages of cell contents or
something like that. But it would need measurements to see if it makes
a difference.

Regards,
Elvis