Add blur parameter to CRT settings

Closes #30

Author: smokku

src/common/gfx.c

@@ -188,6 +188,7 @@ gfx_crt_params_t gfx_crt_default_params(void) {
         .curvature          = 0.10f,
         .gamma              = 1.10f,
         .vignette           = 0.25f,
+        .blur               = 0.35f,
     };
 }
 
@@ -608,6 +609,7 @@ void gfx_draw(chips_display_info_t display_info) {
             .curvature          = state.display.crt_params.curvature,
             .gamma              = state.display.crt_params.gamma,
             .vignette           = state.display.crt_params.vignette,
+            .blur               = state.display.crt_params.blur,
         };
         sg_apply_uniforms(UB_display_crt_fs_params, &SG_RANGE(crt_uniforms));
     } else {

src/common/gfx.h

@@ -40,6 +40,7 @@ typedef struct {
     float curvature;
     float gamma;
     float vignette;
+    float blur;
 } gfx_crt_params_t;
 
 void gfx_init(const gfx_desc_t* desc);

src/common/shaders.glsl

@@ -69,8 +69,7 @@ layout(binding=0) uniform display_crt_fs_params {
     float curvature;
     float gamma;
     float vignette;
-    float _pad0;
-    float _pad1;
+    float blur;
 };
 in vec2 uv;
 out vec4 frag_color;
@@ -97,7 +96,13 @@ void main() {
         frag_color = vec4(0.0, 0.0, 0.0, 1.0);
         return;
     }
-    vec3 col = texture(sampler2D(crt_tex, crt_smp), wuv).rgb;
+    // 3-tap horizontal blur — simulates CRT analog bandwidth limit.
+    // Offset is in UV scaled by output_size so the blur is ~1 output pixel
+    // wide at blur=1.0; weights collapse to identity when blur=0.
+    float ox = blur / max(output_size.x, 1.0);
+    vec3 col = texture(sampler2D(crt_tex, crt_smp), wuv).rgb * 0.5
+             + texture(sampler2D(crt_tex, crt_smp), vec2(wuv.x - ox, wuv.y)).rgb * 0.25
+             + texture(sampler2D(crt_tex, crt_smp), vec2(wuv.x + ox, wuv.y)).rgb * 0.25;
     float scan_phase = wuv.y * output_size.y;
     float scan = 1.0 - scanline_intensity * (1.0 - cos(scan_phase * 3.14159265)) * 0.5;
     col *= scan;

src/ui/ui_crt.h

@@ -107,6 +107,7 @@ void ui_crt_draw(ui_crt_t* win) {
         changed |= ImGui::SliderFloat("RGB mask",   &p.mask_intensity,     0.0f, 1.0f);
         changed |= ImGui::SliderFloat("Curvature",  &p.curvature,          0.0f, 1.0f);
         changed |= ImGui::SliderFloat("Vignette",   &p.vignette,           0.0f, 1.0f);
+        changed |= ImGui::SliderFloat("Blur",       &p.blur,               0.0f, 1.0f);
         changed |= ImGui::SliderFloat("Gamma",      &p.gamma,              0.5f, 2.5f);
         if (changed) {
             gfx_crt_set_params(p);