MacOS drawing on 2x screen super slow?

Desktop & Console
1

if you put this in a Window Paint event:

Dim p As New Picture( 256, 256, 32 )
p.Graphics.ForeColor = CMY(Rnd,Rnd,Rnd)
p.Graphics.FillOval 0,0,256,256
Dim t As Double = Microseconds

For x As Integer = 1 To 20
For y As Integer = 1 To 20
g.DrawPicture p, x*10,y*10
Next
Next
t = (Microseconds-t) / 1000000

Self.Title = Str(t)

Resize the window on a laptop screen and then do it on external monitor.

On my laptop screen( 2x) it’s a lot slower than on an external thats 1x
I’m seeing up to about 30x slower

Anyone else seeing this ?

2

Nope. Roughly same speed on either display. Of course, my external display has roughly the same resolution as my Retina laptop (3440x1440 vs 2880x1800). Time averaged around 0.002 seconds.

3

what does the title in the window say ?
drag it from one to the other
are both 1x or 2x or do they vary ?
here I see as much as a 30x difference (1x way faster)

4

First up on a Retina display you’re using bi-linear or bi-cubic scaling (I forget which one exactly).

Recommendations:

  1. use window.bitmapforcaching to get a pixel perfect image on the first line.
  2. graphics.antialias = false, draw picture, re-enable.
  3. Use CoreGraphics declares to disable the high quality scaling of images.

We talked about improvements with images on this thread Efficient Canvas Drawing

5

On my iMac27" it takes 3.36 seconds. 5120x2880 Retina
If I drag the window to my 19" screen it take 0.10 seconds 1280x1024 NonRetina

6

30 x slower on retina :frowning:

7

This wasnt to try and figure out how to optimize it just “is it really this much slower on retina?”

there’s at least 4x as many pixelsin a retina screen with a windows of the same size
but I sure wouldnt expect 30x difference which is what I see

8 
[1000000](tel:1000000)

what is that?
I changed it to just 1000000

9

OH… this forum thought is was a PHONE#?

10

I guess ???

11

Because it’s a not a fair comparison.

The problem is that the code is drawing a 1x image on a 2x screen, by default this incurs up-scaling, which incurs resampling.

A fair test would be to replace

Dim p as new Picture

with

Dim p as new picture = window.bitmapForCaching( 256, 256 )

Then no up-scaling would take place on either.

How do you get the forum to format Xojo code?

12

with 3 back quotes ( the one under the tilde)
then “xojo”
write your code
close with 3 back quotes

that said you think the upsample would make it 30x slower?

edit : apparently it does
2x is still slower but its close to 4x which isnt unreasonable given there are 4x as many pixels

1 Like
13

Yeah sorry I hadnt noticed that in what I posted