Re: a graphics issue I can not figure out

It's been a while, but note that wx.lib.FloatCanvas was designed
specifically to solve these kinds of problems :-)

https://wxpython.org/Phoenix/docs/html/wx.lib.floatcanvas.html

-CHB


On Thu, Mar 5, 2020 at 6:05 AM Nathan smith <[email protected]> wrote:

> Hello!
>
> I actually did not know that and have thus, slapped myself (virtually) in
> the face.
>
> That would actually explain quite a bit.
>
> I was thinking 0 0 was in the bottom left hand corner of the screen.
>
> thank you, Rufus for your pointing out what I'm sure was an obvious logic
> error to everyone else, you've made this little project make a lot more
> sense :)
>
> Tim, as always, your advice is extremely valuable and often times I find
> myself coming back to your emails on other projects and going "Now hang on
> a second here... Aha, yes Tim mentioned that when answering that question."
>
> Thank you so much again.
>
> Nathan
> On 05/03/2020 05:33, Tim Roberts wrote:
>
> On Mar 4, 2020, at 3:58 PM, Nathan smith <[email protected]> wrote:
>
>
> My goal was to create a grid and then plot some lines upon it.
>
> I have got the grid working, but I can not seem to position a triangle
> correctly.
>
>
> I have a bad habit of making stylistic comments about submitted code.
>
> You should not be storing “dc” and “pen” in a member.  That is, you should
> use “dc” and “pen”, not “self.dc” and “self.pen”.  You need those objects
> to evaporate when the function returns, otherwise things don’t get cleaned
> up.
>
> You can draw the horizontal and vertical grid lines in a single loop:
>
> x0 = g.center_point[0]-6*38
> y0 = g.center_point[1]-6*38
> x1 = g.center_point[0]+5*38
> y1 = g.center_point[1]+5*38
> for x in range(11):
>     dc.DrawLine( x0, y0+x*38, x1, y0+x*38 )
>     dc.DrawLine( x0+x*38, y0, x0+x*38, y1 )
>
>
> Rufus nailed your other issue.  (0,0) in Windows, X, and MacOS is the
> upper left and Y increases going down.  In Postscript and OS/2, (0,0) is
> the lower left and Y increases going up.
>
> I hope you realize that 38 pixels per centimeter is only a rough
> approximation.  Windows lies about the actual pixel size, because in
> reality it has no idea how large your monitor is physically.  38 per
> centimeter maps to 96 pixels per inch.  A 22” monitor running full HD would
> be 96 dpi, but most people have pixels bigger than that.
> —
> Tim Roberts, [email protected]
> Providenza & Boekelheide, Inc.
>
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