Post chain: Shadertoy passes compiled by glslc; Crt, Ripple and Glitch rewritten as Shadertoy files

Stage 9 of docs/render-pipeline.md. src/gui/Post.zig runs the chain over
the finished frame: each pass reads the one before, ping-pong textures
between, the last writes the window; an empty chain is the direct path.
The prefix (shaders/post/prefix.glsl) is ghostty's uniform block, name
for name and offset for offset (tested against a copy of its Uniforms, the
selection colours by their GLSL names), at SDL GPU's bindings, y down.

A user's file (Shader <path>) is compiled by glslc with compileGlsl's own
flags on a thread of its own, taken in at the next loop step; errors name
the file's own lines; a failed compile keeps the last good pipeline;
glslc missing is said once. The bundled passes compile with the build,
through the same prefix.

Crt, Ripple and Glitch are Shadertoy files, rewritten: no barrel (input is
identity, tested), everything in linear light and dithered, keyed to iTime.
scene_effects, crt.zig and crt.frag.glsl are gone; the core keeps no clock
for the chain. ShaderAnimation off|on|always drives redraw level A: the
chain alone over the retained frame (34 us CPU a redraw, measured).

Shared files touched: pardes.zig (nextWake loses the scene line,
disableSceneEffects empties the chain, two tests), builtins.zig (one switch
arm), ninep/ctl.zig (two switch arms), macos.zig (flags from the chain),
gui.zig. Not touched: Messages.zig, mouse.zig, detached/*, host_io, tty.

1 files changed, 16 insertions, 7 deletions

diff --git a/src/effect_sources.zig b/src/effect_sources.zig
index 08680860..6ce11160 100644
--- a/src/effect_sources.zig
+++ b/src/effect_sources.zig
@@ -11,8 +11,11 @@ const ui_vertex_path = shader_dir ++ "ui.vert.glsl";
 const ui_fragment_path = shader_dir ++ "ui.frag.glsl";
 const image_vertex_path = shader_dir ++ "image.vert.glsl";
 const image_fragment_path = shader_dir ++ "image.frag.glsl";
-const scene_vertex_path = shader_dir ++ "crt.vert.glsl";
-const scene_fragment_path = shader_dir ++ "crt.frag.glsl";
+const post_vertex_path = shader_dir ++ "post.vert.glsl";
+// The bundled post passes as compiled: the prefix and the pass together.
+const post_crt_path = shader_dir ++ "post-crt.frag.glsl";
+const post_ripple_path = shader_dir ++ "post-ripple.frag.glsl";
+const post_glitch_path = shader_dir ++ "post-glitch.frag.glsl";
 
 pub const Backend = @TypeOf(build_config.platform);
 pub const backend: Backend = build_config.platform;
@@ -45,13 +48,15 @@ pub const files = switch (backend) {
     },
     .gui => [_]filesystem.Source{
         .{ .path = "src/gui/gui.zig", .contents = @embedFile("gui/gui.zig") },
-        .{ .path = "src/gui/crt.zig", .contents = @embedFile("gui/crt.zig") },
+        .{ .path = "src/gui/Post.zig", .contents = @embedFile("gui/Post.zig") },
         .{ .path = ui_vertex_path, .contents = @embedFile("effect-source-ui.vert.glsl") },
         .{ .path = ui_fragment_path, .contents = @embedFile("effect-source-ui.frag.glsl") },
         .{ .path = image_vertex_path, .contents = @embedFile("effect-source-image.vert.glsl") },
         .{ .path = image_fragment_path, .contents = @embedFile("effect-source-image.frag.glsl") },
-        .{ .path = scene_vertex_path, .contents = @embedFile("effect-source-crt.vert.glsl") },
-        .{ .path = scene_fragment_path, .contents = @embedFile("effect-source-crt.frag.glsl") },
+        .{ .path = post_vertex_path, .contents = @embedFile("effect-source-post.vert.glsl") },
+        .{ .path = post_crt_path, .contents = @embedFile("effect-source-post-crt.frag.glsl") },
+        .{ .path = post_ripple_path, .contents = @embedFile("effect-source-post-ripple.frag.glsl") },
+        .{ .path = post_glitch_path, .contents = @embedFile("effect-source-post-glitch.frag.glsl") },
     },
     .macos => [_]filesystem.Source{
         .{ .path = "src/macos/Sources/PardesView.swift", .contents = @embedFile("macos/Sources/PardesView.swift") },
@@ -69,8 +74,12 @@ pub fn forSetting(setting: config.Runtime.Setting) ?[]const []const u8 {
             .macos => &.{ "src/layout.zig", "src/pardes.zig", "src/macos/Sources/PardesView.swift", "src/macos/Sources/ScenePostprocessor.swift", "shaders/crt.ci.metal" },
             .web, .esp32p4 => null,
         },
-        .scene => switch (backend) {
-            .gui => &.{ "src/gui/crt.zig", "src/gui/gui.zig", scene_vertex_path, scene_fragment_path },
+        .scene => |effect| switch (backend) {
+            .gui => switch (effect) {
+                .crt => &.{ "src/gui/Post.zig", "src/gui/gui.zig", post_vertex_path, post_crt_path },
+                .ripple => &.{ "src/gui/Post.zig", "src/gui/gui.zig", post_vertex_path, post_ripple_path },
+                .glitch => &.{ "src/gui/Post.zig", "src/gui/gui.zig", post_vertex_path, post_glitch_path },
+            },
             .macos => &.{ "src/macos/Sources/PardesView.swift", "src/macos/Sources/ScenePostprocessor.swift", "shaders/crt.ci.metal" },
             .tty, .web, .esp32p4 => null,
         },