[QGIS-Developer] QGIS 3.0 Sluggish on MacOS 10.13 with Retina Display

[Jeremy Palmer]

Hi Nyall,

On Wed, Feb 21, 2018 at 6:51 PM, Nyall Dawson <nyall.dawson at gmail.com>
wrote:
>
>
> I'm just saying that there's nothing QGIS specific there - so there's
> no clues there wherever it's a generic Qt issue or a QGIS regression.
>

I'm using xcode's instruments, but I've never really developed in any code
on MacOSX before. I will see what else can be dumped.


>
> I'm not familiar with OSX - can you set the monitor resolution
> manually? something like 1280 x 800 would be a good test.


I set the screen scale to 1280 x 800. It made some improvement in speed,
but QGIS 3.0 still is running much slower than 2.18.

I also tried enabling the Low Resolution mode for the app bundle as per
[1]. This setting forces the device pixel ratio to 1 from 2 for HiDPI
supported applications. e.g
qgis.utils.iface.mainWindow().devicePixelRatio() = 1. This of course forces
the UI to low resolution and reverses all of the QGIS 3.0 SVG icons work :( The
results were:

1. The QGIS 3.0 mapcanvas UI interactions seemed smoother due to the
increased frame-rate for redrawing the zoom rubberband box or moving the
the cursor.
2. But, the canvas redraws were still just and slow as a device pixel ratio
of 1. i.e The profiling still showed the same amount of CPU time

Here's the results of my benchmarking:

[image: Inline image 1]

Note: canvas size was determined using qgis.utils.iface.mapCanvas().size()

Before I proceed with further profiling it would be good to know if other
mac developers also see performance slowdowns like I do?

Cheers,
Jeremy

* [1] https://support.apple.com/en-nz/HT202471
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