Re: a graphics issue I can not figure out

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] 
> <mailto:[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] <mailto:[email protected]>
> Providenza & Boekelheide, Inc.
>
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