We have four coordinate systems:<br>1) image<br>2) viewport - scaled image coordinates (takes into account zoom-level and image resolution)<br>3) widget ~ viewport transalted on "origin"<br>4) canvas ~ widget translated on "offset"<br>
<br>I'm very unsure about 3 and 4. What do they do actually? And why can't we join both translations?<br><br>As for mirroring, i think all the translation between 1<->2 should be moved into KisCanvas2, then you need to change only two functions and a flip flag to get mirroring.<br>
<br><div class="gmail_quote">On Wed, Mar 24, 2010 at 10:30 PM, <a href="mailto:LukasT.dev@gmail.com">LukasT.dev@gmail.com</a> <span dir="ltr"><<a href="mailto:lukast.dev@gmail.com">lukast.dev@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">Hello,<br>
<br>
I'm trying to implement the mirroring of the canvas. It is a feature where we<br>
mirror the projection of the canvas instead of the mirroring the device when<br>
you want to see mirrored image of your paint. Similar feature is in mypaint.<br>
<br>
I started with mirroring the events. There are some coordinate systems in<br>
canvas. First one is widget space, it is possition of the input device in<br>
widget pixels. Then there is document space, so when you paint, the event from<br>
the widget is converted by few function calls to document coordinates.<br>
<br>
First the coordinates are translated by scrolling offset (when you move with<br>
slider in bigger zoom ) and by document origin (it is the distance from the<br>
canvas top left corner to image top left corner). Then the coordinates<br>
are transformed to document coordinates with zoom.<br>
<br>
I mirror the coordinates on document level, that means that when you draw<br>
stroke, the document is updated in the mirrored part. Document adds the "dirty<br>
rects on document level" so the projection is computed properly because so far<br>
projection does not know about mirroring.<br>
<br>
Next step was to mirror the canvas. I mirrored the projection by QPainter<br>
as Cyrille suggested using transformation like scale(-1,1) and<br>
translate(width,0)<br>
<br>
Now the problems started to show up. The projection with mirrored canvas is<br>
not updated properly. So I started to investigate.<br>
In KisCanvas2::updateCanvasProjection I tried to mirror the vRect rectangle.<br>
The rc rectangle update the projection and the vRect is responsible to for<br>
proper updates calls.<br>
<br>
So far I have these problems:<br>
the canvas is not updated properly, I mirrored the vRect like this<br>
vRect = QRect(image()->width() - vRect.x()<br>
vRect.width(),vRect.top(),vRect.width(), vRect.height());<br>
<br>
but that is not correct. The canvas is erased in QRect<br>
KisPrescaledProjection::preScale(const QRect & rc)<br>
<br>
<br>
If I call just update(), when the whole canvas is updated, it is correct.<br>
What I miss there?<br>
<br>
Question: how to solve it? I don't know much about projection even I spent a<br>
lot of time looking at the code. Dmitry, what do you think I need to do?<br>
Is it correct to mirror the QPainter or should we mirror on the projection<br>
level? If so, what has to be mirrored?<br>
<br>
Another problem. When we zoom and scroll vertically, part of the image is<br>
erased. It seems that when we mirror the image, the hidden part because<br>
actually visible and in the projection it is represented by transparent pixel.<br>
Is that what is happening? Any hints where and how to fix it?<br>
<br>
Here is the patch I have for now<br>
<a href="http://valdyas.org/%7Elukast/mirroring.patch" target="_blank">http://valdyas.org/~lukast/mirroring.patch</a><br>
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</blockquote></div><br><br clear="all"><br>-- <br>Dmitry Kazakov<br>