Does anything but Windows offer this?

Yes. Mac os has many in fact


and more.

i don't know about linux, but pretty sure it does. either way these two dominate over 90% of desktop games

For information, a similar bar is possible on Ubuntu 22.04. It's observable by copying a large file from the file manager:

This is Gnome; I did not check if other desktop environments support it.

KDE also seems to support this.

Sure, this sounds like a great feature for SDL 3.0. Feel free to submit a PR for it.

There's one caveat on the Linux side.

Those progress bars are implementations of the Unity Launcher API... which, in a design which is not typical for such D-Bus APIs, gratuitously requires that the application refer to itself by naming an installed .desktop file.

Here are some relevant resources:

• https://stackoverflow.com/questions/43875343/kde-taskbar-progress
• https://askubuntu.com/questions/158347/how-do-i-make-the-launcher-progress-bar-work-with-my-application
• https://wiki.ubuntu.com/Unity/LauncherAPI

Alright, chiming in on how the API should look like.

In Windows, taskbar progress is implemented through ITaskbarList3 COM interface. More specifically, the ITaskbarList3::SetProgressState and ITaskbarList3::SetProgressValue is the most important one. Taskbar progress has these states:

• None (no taskbar progress)
• Indeterminate (shown as green but cycles the progress bar)
• Normal (shown as green)
• Paused (shown as yellow)
• Error (shown as red)

Reading the Ubuntu Unity Launcher API, it only expose 2 state: visible progress or invisible progress. However it also has "urgency" state. If my assumption is right, this means it's possible to emulate "error" state by setting the "urgency" with visible progress.

Based on capability of those 2, I propose this API:

typedef enum SDL_ProgressState {
    SDL_PROGRESS_STATE_NONE,
    SDL_PROGRESS_STATE_NORMAL,
    SDL_PROGRESS_STATE_ERROR,
} SDL_ProgressState;

bool SDL_SetWindowProgressState(SDL_Window *window, SDL_ProgressState state);
bool SDL_SetWindowProgressValue(SDL_Window *window, double value);

For SDL_SetWindowProgressValue, the value is between 0.0 and 1.0, inclusive.

There's no "getter" function for those. Application is responsible on tracking the states themselves. It's safe to assume newly created SDL_Window* has SDL_PROGRESS_STATE_NONE progress state with value of 0.0.

I'm not sure what states are available for macOS, but if it has "paused" state then we can add an additional SDL_PROGRESS_STATE_PAUSED which is also supported in Windows.

As for the number badges, Ubuntu Launcher API seems have API for it. macOS should have a way to show it (as per above screenshot). However, Windows is the problematic one as it only offers generic "icon overlay" API which means the number badge icon must be supplied manually.

I might give this a try once I'll be done with my current tasks. If someone else wants to try, please leave a comment here so that I don't duplicate the efforts :)

I can work on the Windows backend for this, although I'm gonna leave it to you for the boilerplate. I don't have the confidence to create boilerplate for this, so go ahead.

I submitted a PR for this feature: #12530