gui: the ground is the theme's own background, not a hand-agreed #121212

The SDL shell painted 18,18,18 behind the grid and inside every cell the core
left at its default background, whatever the theme was wearing. Under a light
theme that is a black line along the bottom and right edges of the window --
the strip left over when the window is not a whole number of cells -- measured
two pixels tall with acme at 1728x2102.

The ground is now core.theme().bg, read once a frame, the way PardesView reads
pardes_theme_bg: a Theme command takes hold without a relaunch, and it is the
theme's OWN background rather than the animated chrome colour, because
document backgrounds switch the instant the theme does.

The other half of the macOS fix does not port. A theme that declares no
background (the curated dark, every vendored *_transparent) goes see-through
over an NSVisualEffectView there; here it keeps the terminal-native dark,
because SDL's GPU API refuses to claim a SDL_WINDOW_TRANSPARENT window at all
-- 'The GPU API doesn't support transparent windows', SDL_gpu.c, since D3D12
has no transparent swapchain. Tried it: the shell fails at
ClaimWindowForGPUDevice and exits. bg_default now says so where the next
person will look for it.

Verified on a real window under niri: with Theme acme the bottom strip is
#ffffea where it was #121212.

0 files changed, 0 insertions, 0 deletions