Earlio

Please ignore - somehow Overlay had been selected and this is why the paintbrush was not working on the masks.
I accept that I should check more carefully...

I have been helping out a friend with AP, and was trying (somewhat desperately) to explain how Curves and Blend Ranges work, eventually I made the two attached graphics.
I hope that they will assist, and if anyone has ideas on how to improve (or correct) the Helper Images, please contribute.
 
 

I have been helping out a friend with AP, and was trying (somewhat desperately) to explain how Curves and Blend Ranges work, eventually I made the two attached graphics.
I hope that they will assist, and if anyone has ideas on how to improve (or correct) the Helper Images, please contribute.
 
 

I have been helping out a friend with AP, and was trying (somewhat desperately) to explain how Curves and Blend Ranges work, eventually I made the two attached graphics.
I hope that they will assist, and if anyone has ideas on how to improve (or correct) the Helper Images, please contribute.
 
 

Hi Leigh,
I am delighted to report that I have not had an issue with Affinity Photo and File Preferences since giving Full Disk Access.  Thank you, I am now again using Affinity Photo as my Photo Editor of choice.
Thanks to everyone who contributed to this thread.  The journey has been long and arduous, but have now finally reached the destination.
Earlio

I have been helping out a friend with AP, and was trying (somewhat desperately) to explain how Curves and Blend Ranges work, eventually I made the two attached graphics.
I hope that they will assist, and if anyone has ideas on how to improve (or correct) the Helper Images, please contribute.
 
 

Hi Leigh,
Thank you for the reply and the work you have put in with the log file.
I had given access to Full Disk Access previously, but along the line, with several reloads of AP, and two complete clean installs of Catalina, I had forgotten to do so with the latest install iteration.
I have done so now, completed a restart, and will report if this helps.  I have been avoiding using AP due to the issues, except in a few cases, and had taken to immediately saving any file loaded to AP (after RAW conversion), and setting up the Autosave to every 30 seconds, to try to get around the permissions issues.  It works, after a fashion (when the issue raises it head, I have to do a Force Quit and pick up the recovery file) but that is obviously not an ideal fix...
I will try again with AP as my primary editing app, and keep you informed.

Hi Leigh,
Thank you for the response.
I now have the Console up and running, and I am awaiting an open or save failure, it is intermittent, and will report when the issue occurs again.
I appreciate the help, as I really (REALLY) would like to end my connection with Adobe.

 

Hi Leigh,
I had completed this previously, and should have responded and thanked you for the suggestion.  Apologies.
Although I would consider myself quite familiar with the Mac, I have not had recourse to the Console previously, and I admit to being at a bit of a loss as to where / what I should be looking for.
I did the whole Console, searched (in all the various categories / headings) for Affinity: Sandbox: Font - found no issues with fonts, but got the attached report, which would seem to point to another issue.  
Earlio
Console Affiinty Photo.pdf

Hi Kls,
I am sorry that you are experiencing the same issues as many of us.
Serif are not very customer focussed, and this results in them ignoring such issues, especially when many do not suffer the same problems (or at least do not either realise or simply accept, the limitations).
As has already been pointed out by Chris M, this was a deliberate move by the developers in order to prevent CPU usage increasing.  
Quote: "So the fact we do not allocate additional CPU power in Photo Persona should apply to any Histogram. I do not think it should be taking as long as it does in your video to update. A second or two I could probably live with but your delay was substantial." Unquote
You'll not that I started this thread on 4th June - 5 months and no action whatsoever.  Last time I had issues with Affinity Photo it took 7 months to get some kind of update (when this version was released), and although I use it from time to time, I am sorry that I wasted my money (and so much time...) on this app. I bought the book, worked through the videos and was very happy with the app until the Mojave update.  I guess you get what you pay for - I am back using PhotoShop.
Thank you for the input.

Since I bought a new iMac (febr. 2019), I'm using Affinity Photo (I didn't like the cloud-based version of Photoshop). In the meantime, I've stumbled into so many unsolved bugs, erratic behavior and (worst of all) no solutions, or even reasonable comments from Serif, that I decided to download the free test-version of Adobe Photoshop and . . . . what a relief. Everything runs like clockwork; consistent, responsive and solid. OK, it's 4 times the price, but 10 times worth it. Sorry Serif, I liked you're initiative, but it's not a matter of smart programming alone to bring a competing program to the market. Dealing with customers is an important part of the "look and feel" of a product. And on that part you've got a long way to go. I'm heading back to "Adobe's nest".

Hi Chris B,
I have no sensible response from Apple, they have basically said this is an issue for the developer.  I have also followed the advice of Apple and completed a clean install of Mojave.
OK, I have been spending a lot of time trying to replicate the behaviours of AP with the Levels graph.
On the Levels graph the biggest delays seem to be when working with selections, as you have noted.  However there are still times when the graph does not update, I have now left on image overnight, with the Mac set to stay awake - after 10 hours, the graph on a selection still fails to appear.  In particular, the smaller the selection, the longer the timespan for appearance of the graph.  I have checked that the Levels Panel has something to work on, having selected a small portion of a a full colour image (approx 300 x 300px) which is monochrome so should give a pretty solid graph, I have tried selection with a number of small areas with in full colour, and the issue remains.  
The controls for the Histogram still work, but the graph (which is designed to be a graphic representation of the image portion) often takes an inordinate amount of time to update, sometimes not updating at all.
Frustrating.

Hi Chris,
The Metal issue would seem to be a recurring theme with my 2017 MacBook. It is extensively discussed in another thread.  Metal is enabled.
I  waited more than 7 months for the update to solve the Metal Acceleration issues post Mojave update, and could not use Affinity Photo during that time due to the lack of speed due to not being able to use Metal at all, and had to go back to Photoshop during this period.
It happens with every image.  It would seem to update immediately in the Develop Personal, I use RAW, so I would have noticed any lag.  I have just tried another image, and it seems to update instantly when back in Develop Persona.  The Levels layer seems to remember the last setting, and this may be where the issue lie, I cannot think of a reason to retain the setting for the previous image in Levels.  I have also noted that the update of the graph (Histogram) in Levels is particularly slow when working on a selection.
I have tried with Metal disabled, and the issue does not seem to replicate.  I tried with several images, but all seemed to update the graph immediately, however turning off Metal is not an option for me due to the long wait when developing RAW files, and the fact that Parallel Processing is then disabled when Batch Processing.
The amount of time taken for the graph to update varies hugely, and sometimes does not update at all (I left one image for over 20 minutes and the graph had still not appeared).  It would seem to have no relationship to the size of the image, to what else is running (I closed down every other app running except Activity Monitor) and the CPU Usage was under 12% - so does not appear to be a resource issue.  You can see the settings being retained in the video. The indicator lines in the initial graph are those from the previous image, and this information would appear to be retained until the graph updates when the lines return to the default 0% Black and 100% White.  There would appear to be no retention of the previous Levels setting with Metal disabled.
Obviously it is not an option to switch between Metal enabled / disabled as this requires a restart, which is time consuming.
MacBook Pro (15-inch, 2017)
2.9 GHz Intel Core i7
16 GB 2133 MHz LPDDR3
I am disappointed that despite a very long wait for a solution, I still cannot use Affinity Photo to its full potential.
 
Screen_Recording_2019-06-25_at_11_37_24.mov

Hi Chris,
Thanks for the quick response.  I have not had an actual crash (as yet) - rather I have the same issue as Anwarp, where APh just hangs, on a couple of images, these have actually saved.
So what is happening:
Save (I save as Affinity Openable .afphoto file - I have not noticed with any Export formats)  - Box comes up "Saving" with meter
APh hangs (the pinwheel starts and the meter halts) and the only way to stop this is to Force Quit
Most of the time, the image has not saved, but on some images, the images has saved, so puzzling.  
Although this appears to be happening randomly, it does seems to be especially prevalent after resizing the image.
I hope this helps.

I am having there same issue - Mojave 10.14.5.  MacBook Pro 15inch 2017 2.9Ghz Intel Core i7.  16Gb Memory.

I have a similar issue with the preferences panes - I work a lot with images that are required at the same size / resolution for clients, and require thumbnails and sample (smaller) images for the client to view.
I asked (way back) that the crop tool should allow user to change default size option. Instead, each time I work on an image where cropping is required, I have to go through the process of selecting Original Ratio for every image, a tiresome and unnecessary repetitive process.
I then Batch Process the images to resize to the required (original) size, and can also run further batch processes to produce thumbnails and sample images in different sizes.
Sticky tool settings, across all Personas would be an excellent upgrade.

I have a similar issue with the preferences panes - I work a lot with images that are required at the same size / resolution for clients, and require thumbnails and sample (smaller) images for the client to view.
I asked (way back) that the crop tool should allow user to change default size option. Instead, each time I work on an image where cropping is required, I have to go through the process of selecting Original Ratio for every image, a tiresome and unnecessary repetitive process.
I then Batch Process the images to resize to the required (original) size, and can also run further batch processes to produce thumbnails and sample images in different sizes.
Sticky tool settings, across all Personas would be an excellent upgrade.