The original Windows and Mac clients didn't use Qt, it appears the Linux version released after did. Here's what I found scouting quora:
> Qt is only used on Linux. The native parts is built with our own custom toolkit on top of a canvas- and window-abstraction layer. The canvas/window stuff is implemented with Qt on Linux, but with native stuff on win/mac. Then we have the HTML5 views, which use Chromium Embedded Framework.
> Proprietary technology written in C++, C and a tad of assembler. A list of third party technology used can be read by going to Help → Show Licenses in Spotify, or by opening file://localhost/Applications/Spotify.app/Contents/Resources/licenses.xhtml (if you're on Mac OS).
> Qt is only used on Linux. The native parts is built with our own custom toolkit on top of a canvas- and window-abstraction layer. The canvas/window stuff is implemented with Qt on Linux, but with native stuff on win/mac. Then we have the HTML5 views, which use Chromium Embedded Framework.
https://www.quora.com/What-is-spotify-Windows-Mac-GUI-app-bu...
> Proprietary technology written in C++, C and a tad of assembler. A list of third party technology used can be read by going to Help → Show Licenses in Spotify, or by opening file://localhost/Applications/Spotify.app/Contents/Resources/licenses.xhtml (if you're on Mac OS).
https://www.quora.com/How-did-Spotify-make-a-multiplatform-l...
The list of deps is insightful looks like they used WTL for their Windows UI, no idea how they made it work on Mac as well:
Boost, Expat, FastDelegate, giflib, libjpeg, libogg, libvorbis, Mersenne Twister, zlib, NSIS (Windows only), Windows Template Library (Windows only), Growl (Max OS X only), Lua