retina not acurate

How to reproduce

• Leaflet version I’m using: 1.3.1 but also on http://leaflet-extras.github.io/leaflet-providers/preview/
• Browser (with version) I’m using: Firefox 60.0.2 or Chromium 66.0.3359.181
• OS/Platform (with version) I’m using: Ubuntu 17.10

What behaviour I’m expecting and which behaviour I’m seeing

Documentation says “detectRetina : If true and user is on a retina display, it will request four tiles of half the specified size and a bigger zoom level in place of one to utilize the high resolution.”

But it’s not used to compute L.Browser.retina (true for browsers on a high-resolution “retina” screen.) var retina = (window.devicePixelRatio || (window.screen.deviceXDPI / window.screen.logicalXDPI)) > 1;

On my screen, window.devicePixelRatio is 2 when browser display is zoomed to 200% so L.Browser.retina is true as soon as display zoom is > 100% and false when browser zoom is < 100%

That is not what “retina” is meant to be.

Minimal example reproducing the issue

• Open browser, zoom display to 150% (this is browser display, not map zoom)
• Browse to http://leaflet-extras.github.io/leaflet-providers/preview/
• Choose Stamen toner or another provider with retina tiles
• Open developer 's javascript console
• See the value for L.Browser.retina
• See the value for window.devicePixelRatio
• Open “Network” tab and see the uploaded tiles : they are @2x version
• Unzoom browser (dont unzoom the map, but the browser display, using its menu)
• See values…

Window has to be refreshed CTRL+F5 after browser display zoom has changed; so retina value is computed anew

[JLuc]

Ok I understand. You’re right about avoiding blurry images.

What now might be improved is the wording and the explanation : both “retina screen” and “high DPI” (dot per inch = screen property) are not fit to describe what L.Browser.retina realy is.

I propose https://github.com/Leaflet/Leaflet/pull/6203

[ghybs]

The steps and result you describe are the expected behaviour.

Although the flag is called “retina”, it targets high DPI, and the case of a natively zoomed browser window is also considered in that category. Now this may be argued upon, but it seems to me that this is for a reason and it does not harm much in any case: why do you absolutely want not to load @2x tiles when your browser window is zoomed? That provides with crisper graphics, instead of blurry zoomed images.