Set application icon from within XIVLauncher.Core

[Dormanil]

So turns out we've been relying on desktop environments to set icons for us, when we could have done that ourselves. Thankfully, since I last touched SDL in this project, we switched to a better C# wrapper, so this was halfway painless.

I am giving SDL the ability to choose from multiple alternate sizes as appropriate for the use case. Initially it was going to contain 48x48, 32x32, 24x24, and 16x16 as alternate sizes as well, like the (in XLCore unused) dalamud_icon.ico provides, but it didn't look good on my machine. I considered using the ico file, but SDL will only actually look at the highest resolution image within it, so I would have to roll my own image loader, which is entirely beyond the scope of this.

During testing on both X11 and Wayland, the new application icon graced my title bar for the first time since switching to XLCore from XL for Windows. It also sets my taskbar icon properly, though I had to remove the currently existing .desktop file because I couldn't see any changes otherwise. We may want to consider removing the StartupWMClass in it or consider setting it to ffxiv_dx11.exe, like someone else suggested, to share the XIVLauncher icon with the game.
Before:

After:

Fixes #363.

[wolfcomp]

This way of handling the error and retun of the function would make it more versitile if there are other places it such as SDL.ScaleSurface which can fail but isn't checked

[wolfcomp]

Suggested change

	if (tempicon is null)
	{
	Log.Error($"Error: SDL_LoadPNG_IO failed: {SDL.GetErrorS()}");
	return SDL.CreateSurface(0,0,SDLPixelFormat.Abgr8888);
	}
	if (tempicon is null)
	{
	icon = null;
	return false;
	}

[wolfcomp]

Suggested change

	icon = GetApplicationIcon();
	SDL.SetWindowIcon(window, icon);
	if(!GetApplicationIcon(out icon))
	{
	Log.Error($"Error: Could not get application icon correctly: {SDL.GetErrorS()}");
	}
	else
	{
	SDL.SetWindowIcon(window, icon);
	}

[mihawk90]

We may want to consider removing the StartupWMClass in it or consider setting it to ffxiv_dx11.exe, like someone else suggested, to share the XIVLauncher icon with the game.

That was me, and the commit is ready, I just had some more testing to do after making it and then got caught up in other stuff (the issue this addresses among other things). I'll see if get around to opening the PR tomorrow.

---

Just one question regarding this PR:
Maybe I'm missing it, but this sets the icon with a static graphic, correct? Does SDL provide a way to set it by icon name? That would allow it to follow user's icon themes too (not important, but nice to have).

[Dormanil]

Just one question regarding this PR:
Maybe I'm missing it, but this sets the icon with a static graphic, correct? Does SDL provide a way to set it by icon name? That would allow it to follow user's icon themes too (not important, but nice to have).

As far as I can tell, SDL does not provide a way to set an icon by its name, in fact, SDL discourages loading images into memory with its LoadPNG methods:

This is intended as a convenience function for loading images from trusted sources. If you want to load arbitrary images you should use libpng or another image loading library designed with security in mind.

Best I can do ignoring SDL's suggestions is looking up the icon theme, figuring the file out from there, and loading it by file name. Problem with that is that there is no desktop-agnostic way of getting the user's icon theme, so now I have to support multiple code paths based on the user's preference of Qt vs GTK, in addition to the current method as the macOS and Windows fallback.

[Dormanil]

@wolfcomp I was quite happy with moving to the TryParse pattern, but I would prefer actually knowing which of the SDL calls failed if we're going with it.

[mihawk90]

Best I can do ignoring SDL's suggestions is looking up the icon theme, figuring the file out from there, and loading it by file name.

Yeah no, don't bother with that then, it's just a luxury anyway 😄