Thanks for that added bit of knowledge, Emile! Actually, never gave thought to the fact that “screen resolution” was anything but the 72/96 dpi since I’ve dealt with those numbers for so long now. The newer monitors with the higher def would have to be increased pixel density by their very definition, I reckon. So far, I haven’t faced that with my industrial clients (whose equipment is decidedly older vintage and my programs are aligned with that) but I will keep your warning in the forefront of my thought process moving forward since I am certain I will encounter it sometime soon. Again, thanks for taking your time to add that fact to the discussion, Emile!
Screen resolution is on it’s way to increase, as technology evolves. Already, iPhone 6 Retina is 3x, meaning 216 dpi.
Yet, from a Xojo app perspective, you may want to keep in mind that the elementary point is still 1/72th an inch.
That is the way Apple Retina screens work too. A point on a Retina 2x screen represents 4 pixels. The way Apple manages that is though API calls that as of yet Xojo does not handle. So it is not possible to display natively a picture with a 144 dpi resolution. You would have to use for instance Retina Kit 2 from Sam Rowland’s Ohanaware.com
It becomes a little thornier on Windows HDPI screens, where fonts and applications have to be scaled according to the resolution (just like between an 800x600 and 1920x1080 screen). In other words, on a high DPI screen such as what Emile describe, you will have to make your windows, controls and fonts 1.67 times larger to get the same display dimensions as on a regular 72 dpi screen.
It’s all bollox now as screens have been higher resolution than 72 Dpi for so long!
I recall being able to hold a sheet of paper on the screen as it really was wysiwyg.
Quick calculation 15" Retina MacBook Pro has a horizontal resolution of 2880, with the screen being about 13" wide. Which makes it about 222 DPI. The OS (by default) draws at 144 DPI, so in theory to view something at WYSIWYG (72 DPI) you’d need to scale your documents to 150%.
Anyway, just a passing thought.
So again, let me see if I got this straight … at the end of the day, this is the starting point of any “visual output” design efforts when using Xojo whether for print (graphics layer) or screen display (e.g., control, etc.)??? Is that a fair way of stating it?
All you need to worry about is working in 72 PPI (not DPI), let the OS handle the conversion for print or display.
So, kinda like that song, “It’s All About The Bass”, but instead of thinking “It’s all about the bass, bout the bass, no treble”, I have to think, “It’s all about the pixels, bout the pixels, no dots” ^^
It’s all about points, no matter the number of pixels 
The point is a typographical measurement of 1/72th an inch that has for some reason been taken as reference for screen a while ago.
Thanks, Michel and Sam … I think you’ve convinced me to go read some more about points vs. pixels vs. dots.
Sorry I didn’t make that clear, Michel’s right… The other way to think about it is to only work in 72 pixels per inch and let the OS scale it to what ever the output source uses. Both Apple and MS refer to it as points.
The only time you need to actually handle DPI yourself is when working with bitmap images as (OS X) Xojo uses CGImages which are only 72 DPI, if you need higher resolution, then you must draw at 72 DPI and scale the image dimensions and drawing properties. So if you want to create a 300 DPI image, set all your scaling to 5x.
But for on screen and printing, just work in 72 Points per inch.