macos fix

1 files changed, 26 insertions, 0 deletions

diff --git a/src/config.zig b/src/config.zig
index cbe75dea..1a3de86c 100644
--- a/src/config.zig
+++ b/src/config.zig
@@ -566,6 +566,32 @@ pub const gui_topbar_pane_border_px: u8 = 1;
 /// build that wants a deliberate accent can pin one here.
 pub const gui_topbar_pane_border_rgb: ?[3]u8 = null;
 
+/// Open the SDL window with a transparent buffer, so that a theme declaring NO
+/// background of its own (the curated `dark`, every vendored `*_transparent`)
+/// shows the desktop through the grid instead of a colour this shell had to
+/// invent. That is what the AppKit shell does over its NSVisualEffectView, and
+/// on linux the compositor supplies the backdrop — a niri `background-effect
+/// { blur true }` window rule, picom, whatever is running.
+///
+/// OFF by default because it is not free, and the cost is structural rather
+/// than ours: `SDL_ClaimWindowForGPUDevice` refuses a transparent window
+/// outright ("The GPU API doesn't support transparent windows", SDL_gpu.c,
+/// still upstream), because D3D12 has no transparent swapchain and the API
+/// says no everywhere rather than only where it must. A transparent window
+/// therefore has no swapchain to render into, and the frame reaches the screen
+/// down the same readback-and-blit path a compositor that cannot back a Vulkan
+/// swapchain already uses (`soft_present` in `src/gui/gui.zig`): one
+/// GPU->CPU download plus one upload per PAINTED frame, measured at 1.2 ms for
+/// 2240x1440 and 3.0 ms for 3840x2160 on an RTX 3050. Idle frames cost
+/// nothing — this shell only paints when something changed — but an animation
+/// at 60 Hz spends that every frame.
+///
+/// With a theme that DOES bring a background this changes nothing visible: the
+/// ground is painted at full alpha, exactly as an opaque window would. It
+/// still pays the readback, because window transparency is fixed at creation
+/// and a `Theme` command may reach a transparent theme later.
+pub const gui_transparent: bool = false;
+
 /// Touchpad drift guard, in ticks. A two-finger swipe that is MEANT to be
 /// vertical carries a little sideways drift, and the pad faithfully turns that
 /// drift into wheel_left/wheel_right — so a plain scroll slides the view