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Re: New zoom code musings.


jean-pierre charras - INPG wrote:
> Dick Hollenbeck a écrit :
>> Wayne Stambaugh wrote:
>>> Warning, rant ahead. If you are only interested in the new zoom stuff,
>>> skip down to the last paragraph. However, if you indulge me, I would
>>> like to impart some wisdom I gathered on my travels through the inner
>>> workings of Kicad and wxWidgets. Let me start by saying that in order
>>> to get the new zoom features implemented I violated at least a half
>>> dozen of my personal coding rules not the least of which are don't
>>> reinvent the wheel and keep it simple. But I was concerned about Dick's
>>> eye sight, so I acquiesced.: } In my travels through the Kicad and
>>> relevant wxWidgets source code, I came to the following conclusion that
>>> all of the drawing coordinate scaling (zooming) and offsetting code in
>>> Kicad is unnecessary and redundant. For all the developers who in the
>>> past have voiced concerns about using floating point for drawing
>>> coordinate calculations, be assured that it is already happening inside
>>> wxDC. Granted, if no changes to the logical or user scalars are made to
>>> the device context, then the coordinates get multiplied by 1.0 * 1.0.
>>> They still get converted to floating point then back to integer. In
>>> fact, all of the scaling code performed as integers in Kicad just adds
>>> clock cycles to what wxDC already does. There is no performance gain by
>>> doing this. Not convinced, check out the "drawing" sample shipped with
>>> the wxWidgets source. It does not scale the drawing object coordinates
>>> before calling the wxDC drawing methods. All it does to change the size
>>> an position of the drawing is manipulate the user scale and logical
>>> offset of the device context. Everything else is taken care of by wxDC
>>> automatically. wxDC even provides functions to translate coordinates
>>> between the logical and display units. All of this capability appears
>>> to have been available in wxDC all the way back to at least 2.2.9 in
>>> December 2001 (that was the oldest wxWidgets help I could find). The
>>> drawing sample works the same on Windows and Linux (64 & 32 bits). Can
>>> someone with OSX confirm that wxWidgets drawing sample works there as
>>> well? If so, I think that all of the code in gr_basic.cpp and all of
>>> the scaling and offset calculation code scattered throughout Kicad
>>> should be remove and pushed down to wxDC where it belongs. This would
>>> greatly simplify drawing in Kicad and having the added bonus of allowing
>>> the use of some of the more advanced wxDC type classes such as
>>> wxGraphicsContext or wxBufferedDC. I am willing to take on the task
>>> (although it will probably take me a few months to complete) after the
>>> next version of Kicad is released. I'll stop ranting now, but I have a
>>> few more in store for a later date.
>> Good information. Sounds like a good bit of work to change strategy,
>> and tough to straddle a fence while doing it. But if there are no
>> gotchas this seems like a reasonable direction for the package to evolve
>> towards.
>>> Now on to the new zoom code. Due to the coordinate scaling being
>>> scattered throughout Kicad, I did not implement the new zoom code with
>>> #ifdefs all over the place. I started down that path, but it was
>>> quickly becoming an awful mess and a pain to enable and disable. I
>>> tested everything I could think of that is zoom related and it seemed to
>>> work fine for me. There may be some slight single pixel drawing issues
>>> due to rounding since I had to use a scalar to get a zoom of 1.5 (known
>>> as zoom level 15 in the new code). I have not committed the new code to
>>> SVN yet due to talk of a new release in February. If no one has any
>>> objections, I will commit the code in the next few days. I believe that
>>> the risk is fairly low but I will wait. If the consensus is to wait
>>> until after the new release, I'll hold off committing until then.
>> There are always folks who will not touch the SVN version until we say
>> it is a release candidate. These extra users come on board and
>> essentially become testers of the first RC's. I think we can use that
>> extra testing man-power to find and fix any problems with your changes
>> along with all the hundreds of others. The first RC may not be
>> perfect. That is my opinion, so I would lean towards getting it out
>> there. Given your remarks above, this zoom code would not otherwise
>> exist if we pursue a path of pushing it out of App code and down into
>> wxDC. So if not now, then when?
> I agree.
> I think you can commit this new code ASAP.
> the first RC will have a lot of new and complex functions that can have 
> some bugs.
> But if we wait until no bugs, the new RC never happens.

I'll update the changelog and commit the changes sometime today.


>> And if anybody complains, we can always give them a discount. :) In
>> fact, discounts of 100% are feasible.
>> Dick
> Discounts of 100% are feasible only for 2 licenses and more.
> (until now we earned $ 0 million , but expect $ 0 billion tomorrow)