Orgnaization & cleanup

draw/shaders/source/backdrop_blur.frag

@@ -1,19 +1,18 @@
 #version 450 core
 
 // Unified backdrop blur fragment shader.
-// Handles both H-blur (mode 0, blurs the ¼-resolution downsample texture into
-// the ¼-resolution h_blur texture) and V-blur+composite (mode 1, blurs h_blur
-// vertically, masks via RRect SDF, applies tint, composites outline, and writes
-// to the main render target with premultiplied alpha).
+// Handles both the 1D separable blur passes (mode 0, used for BOTH the H-pass and V-pass;
+// `direction` picks the axis) and the composite pass (mode 1, reads the fully-blurred
+// working texture, masks via RRect SDF, applies tint, and writes to source_texture with
+// premultiplied-over blending). Working textures are sized at the full swapchain resolution;
+// downsampled content occupies only a sub-rect at downsample factor > 1 (set via viewport).
 //
-// Following RAD's pattern, V-mode replaces a separate composite pass: the SDF
-// discard limits V-blur work to the masked region, and the per-primitive tint
-// is folded in. Output blends with the main render target via the standard
-// premultiplied-over blend state (ONE, ONE_MINUS_SRC_ALPHA).
+// The composite blends with source_texture via the standard premultiplied-over blend state
+// (ONE, ONE_MINUS_SRC_ALPHA).
 //
-// Backdrop primitives are tint-only — there is no outline. A specialized edge
-// effect (e.g. liquid-glass-style refraction outlines) would be implemented
-// as a dedicated primitive type with its own pipeline.
+// Backdrop primitives are tint-only — there is no outline. A specialized edge effect
+// (e.g. liquid-glass-style refraction outlines) would be implemented as a dedicated
+// primitive type with its own pipeline.
 //
 // Two modes, structurally distinct:
 //
@@ -30,11 +29,11 @@
 //           (gl_FragCoord.xy * inv_downsample_factor) * inv_working_size.
 //           No kernel is applied here — the blur is already complete.
 //
-// Splitting V-blur out of the composite pass (an earlier version combined them) was needed
-// to avoid a horizontal-vs-vertical asymmetry artifact: when the V-blur sampled the H-blur
-// output through the bilinear-upsample/SDF-mask/tint pipeline in one shader invocation,
-// horizontal source features ended up looking sharper than vertical ones. Running V-blur as
-// its own working→working pass (matching H's structure exactly) restores symmetry.
+// V-blur is run as its own working→working pass rather than folded into the composite. The
+// folded variant produced a horizontal-vs-vertical asymmetry artifact: when V-blur sampled
+// the H-blur output through the bilinear-upsample/SDF-mask/tint pipeline in one shader
+// invocation, horizontal source features ended up looking sharper than vertical ones.
+// Matching V's structure exactly to H's restores symmetry.
 
 const uint MAX_KERNEL_PAIRS = 32;
 
@@ -140,16 +139,16 @@ void main() {
     vec2 uv = (gl_FragCoord.xy * inv_downsample_factor) * inv_working_size;
     vec3 color = texture(blur_input_tex, uv).rgb;
 
-    // Tint composition (Option B semantics): inside the masked region the panel is fully
-    // opaque — it completely hides the original framebuffer content, just like real frosted
-    // glass and like iOS UIBlurEffect / CSS backdrop-filter. f_color.rgb specifies the tint
-    // color; f_color.a specifies the tint *mix strength* (NOT panel opacity). At alpha=0 we
-    // see the pure blur; at alpha=255 we see the blur fully multiplied by the tint color.
+    // Tint composition: inside the masked region the panel is fully opaque — it completely
+    // hides the original framebuffer content, just like real frosted glass and like iOS
+    // UIBlurEffect / CSS backdrop-filter. f_color.rgb specifies the tint color; f_color.a
+    // specifies the tint *mix strength* (NOT panel opacity). At alpha=0 we see the pure
+    // blur; at alpha=255 we see the blur fully multiplied by the tint color.
     //
     // Output is premultiplied to match the ONE, ONE_MINUS_SRC_ALPHA blend state. Coverage
     // (the SDF mask's edge AA) modulates only the alpha channel, never the panel-vs-source
-    // blend; that way edge pixels still feather correctly without re-introducing the bug
-    // where mid-panel pixels became semi-transparent.
+    // blend; that way edge pixels still feather correctly while mid-panel pixels stay fully
+    // opaque.
     mediump vec3 tinted = mix(color, color * f_color.rgb, f_color.a);
     mediump float coverage = sdf_alpha(d_n, h_n);
     out_color = vec4(tinted * coverage, coverage);