feat(videoout): use sce_sys/icon0.png as the window icon

[alfalfa-star]

What

The game window now uses the title's icon. When /app0/sce_sys/icon0.png exists, DisplayWindow decodes it with the existing decoder_png (RGBA8) and sets it with SDL_SetWindowIcon right after the window is created.

This completes the icon work:

• fix(relinker): add icons to generated Windows executables #350 embeds icon0.png in the generated Windows .exe. Explorer shows it, and SDL uses it as the window class icon.
• feat(relinker): write a desktop entry with the game icon for Linux executables #353 (open) writes a .desktop entry, so Linux file managers and launchers show the icon.
• This PR sets the icon on the running window. On Linux, an ELF has no icon resource, so the title bar, taskbar and alt-tab showed a generic icon until now. On Windows the call sets the same image again.

The icon bytes come from the existing AppMetadata HasAppIcon/GetAppIconData, which already check the PNG signature. Without icon0.png nothing changes. If the icon can't be decoded, window creation throws, like the other DisplayWindow failures.

libSceVideoOut now links decoder_png. No new dependencies or flags.

Tested

Linux (Arch, KDE Plasma, Wayland session):

• libSceVideoOut builds, and guest_video_out_wqhd_detection passes.
• Standalone check with the same decode and SDL_SetWindowIcon path, a real 512×512 icon0.png and SDL_VIDEODRIVER=x11: _NET_WM_ICON is 512×512, and pixel (100,100) reads 0xffc91312 (ARGB), which matches the decoded RGBA c9 13 12 ff, so the channel order is correct.
• PPSA14632 (LEGO Horizon Adventures), with this commit on a test tree of main plus other open PRs, SDL_VIDEODRIVER=x11 under XWayland: the game window's _NET_WM_ICON (read with XGetWindowProperty) is 512×512, and pixel (100,100) is 0xffc91312, the same as in the standalone check. (xprop prints the property as empty because it is about 1 MiB.)

Not tested: native Wayland (shows only where the compositor supports xdg-toplevel-icon-v1) and Windows.

No automated test: it needs a real window and display, which CI doesn't have.

Checklist

• Based on current main; no other open PR implements the same functions
• One topic per PR; follow-ups go in a new PR
• No comments in code except technical debt
• Unimplemented paths throw (NotImplemented_nid_no_patch); silent stubs are listed in TechnicalDebt
• No notes, investigation .md files or images added to the repository (attach them to this PR)
• New third-party code is a submodule built from source
• Generic behaviour, not specific to one title
• Depends on: none (complements fix(relinker): add icons to generated Windows executables #350 and feat(relinker): write a desktop entry with the game icon for Linux executables #353)
• AI-assisted: yes

🤖 Generated with Claude Code

[oneandonlydean]

The Tested section still has the hidden FILL IN after the game run line; please add the title run or remove it.

[alfalfa-star]

Replaced the placeholder with the title run. On PPSA14632 under XWayland, the game window's _NET_WM_ICON is the 512×512 icon0.png, and a sampled pixel matches the decoded PNG. I read it with XGetWindowProperty, because xprop prints a property that large (about 1 MiB) as empty.

[popcoder565]

Native Windows run, since no Windows results were posted. Setup: Windows 10 (19045), MinGW-w64 GCC 15.2.0 (WinLibs r7), Release. Head 57a529d5, merged onto main 8b393b6 in one build with 31 other PRs that had no Windows run.

• This PR has no test of its own. It builds, and windows_icon and windows_icon_resource pass.
• Full ctest in that build: 520 of 521. The one failure is guest_offline_imports, broken by feat(libSceRudp): implement sceRudpGetStatus #2359 (reported there).

No title was run.

🤖 Addressed by Claude Code

[github-actions]

Other open pull requests touch the same code. Merging one will break the other, or both implement the same thing. If this one builds on them, list them in Depends on.

Pull request	Conflicting files (lines on main)	Same exports	Same new files
#674	core/libs/prx/libSceVideoOut/CMakeLists.txt L19

[adriadam10]

Checked on Linux: builds and full ctest passes (548/548) merged onto current main; CI is green on the head (linux, windows, conventions). The RGBA8 output of Decoder::Png::Decode matches SDL_PIXELFORMAT_RGBA32, and the surface is freed. Windows build confirmed by @popcoder565. Merging.