migrat, amb ajuda de claude, a sdl3gpu (postfx i crtpi) igual que el JDD

data/shaders/crtpi_frag.glsl

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+#version 450
+
+// Vulkan GLSL fragment shader — CRT-Pi PostFX
+// Algoritmo de scanlines continuas con pesos gaussianos, bloom y máscara de fósforo.
+// Basado en el shader CRT-Pi original (GLSL 3.3), portado a GLSL 4.50 con parámetros uniformes.
+//
+// Compile: glslc -fshader-stage=frag --target-env=vulkan1.0 crtpi_frag.glsl -o crtpi_frag.spv
+//          xxd -i crtpi_frag.spv > ../../source/core/rendering/sdl3gpu/crtpi_frag_spv.h
+
+layout(location = 0) in  vec2 v_uv;
+layout(location = 0) out vec4 out_color;
+
+layout(set = 2, binding = 0) uniform sampler2D Texture;
+
+layout(set = 3, binding = 0) uniform CrtPiBlock {
+    // vec4 #0
+    float scanline_weight;          // Ajuste gaussiano de scanlines (default 6.0)
+    float scanline_gap_brightness;  // Brillo mínimo entre scanlines (default 0.12)
+    float bloom_factor;             // Factor de brillo en zonas iluminadas (default 3.5)
+    float input_gamma;              // Gamma de entrada — linealización (default 2.4)
+    // vec4 #1
+    float output_gamma;             // Gamma de salida — codificación (default 2.2)
+    float mask_brightness;          // Brillo sub-píxeles de la máscara (default 0.80)
+    float curvature_x;              // Distorsión barrel eje X (default 0.05)
+    float curvature_y;              // Distorsión barrel eje Y (default 0.10)
+    // vec4 #2
+    int mask_type;                  // 0=ninguna, 1=verde/magenta, 2=RGB fósforo
+    int enable_scanlines;           // 0 = off, 1 = on
+    int enable_multisample;         // 0 = off, 1 = on (antialiasing analítico de scanlines)
+    int enable_gamma;               // 0 = off, 1 = on
+    // vec4 #3
+    int enable_curvature;           // 0 = off, 1 = on
+    int enable_sharper;             // 0 = off, 1 = on
+    float texture_width;            // Ancho del canvas lógico en píxeles
+    float texture_height;           // Alto del canvas lógico en píxeles
+} u;
+
+// Distorsión barrel CRT
+vec2 distort(vec2 coord, vec2 screen_scale) {
+    vec2 curvature = vec2(u.curvature_x, u.curvature_y);
+    vec2 barrel_scale = 1.0 - (0.23 * curvature);
+    coord *= screen_scale;
+    coord -= vec2(0.5);
+    float rsq = coord.x * coord.x + coord.y * coord.y;
+    coord += coord * (curvature * rsq);
+    coord *= barrel_scale;
+    if (abs(coord.x) >= 0.5 || abs(coord.y) >= 0.5) {
+        return vec2(-1.0);  // fuera de pantalla
+    }
+    coord += vec2(0.5);
+    coord /= screen_scale;
+    return coord;
+}
+
+float calcScanLineWeight(float dist) {
+    return max(1.0 - dist * dist * u.scanline_weight, u.scanline_gap_brightness);
+}
+
+float calcScanLine(float dy, float filter_width) {
+    float weight = calcScanLineWeight(dy);
+    if (u.enable_multisample != 0) {
+        weight += calcScanLineWeight(dy - filter_width);
+        weight += calcScanLineWeight(dy + filter_width);
+        weight *= 0.3333333;
+    }
+    return weight;
+}
+
+void main() {
+    vec2 tex_size = vec2(u.texture_width, u.texture_height);
+
+    // filterWidth: equivalente al original (768.0 / TextureSize.y) / 3.0
+    float filter_width = (768.0 / u.texture_height) / 3.0;
+
+    vec2 texcoord = v_uv;
+
+    // Curvatura barrel opcional
+    if (u.enable_curvature != 0) {
+        texcoord = distort(texcoord, vec2(1.0, 1.0));
+        if (texcoord.x < 0.0) {
+            out_color = vec4(0.0, 0.0, 0.0, 1.0);
+            return;
+        }
+    }
+
+    vec2 texcoord_in_pixels = texcoord * tex_size;
+    vec2 tc;
+    float scan_line_weight;
+
+    if (u.enable_sharper != 0) {
+        // Modo SHARPER: filtrado bicúbico-like con subpixel sharpen
+        vec2 temp_coord = floor(texcoord_in_pixels) + 0.5;
+        tc = temp_coord / tex_size;
+        vec2 deltas = texcoord_in_pixels - temp_coord;
+        scan_line_weight = calcScanLine(deltas.y, filter_width);
+        vec2 signs = sign(deltas);
+        deltas.x *= 2.0;
+        deltas = deltas * deltas;
+        deltas.y = deltas.y * deltas.y;
+        deltas.x *= 0.5;
+        deltas.y *= 8.0;
+        deltas /= tex_size;
+        deltas *= signs;
+        tc = tc + deltas;
+    } else {
+        // Modo estándar
+        float temp_y     = floor(texcoord_in_pixels.y) + 0.5;
+        float y_coord    = temp_y / tex_size.y;
+        float dy         = texcoord_in_pixels.y - temp_y;
+        scan_line_weight = calcScanLine(dy, filter_width);
+        float sign_y     = sign(dy);
+        dy = dy * dy;
+        dy = dy * dy;
+        dy *= 8.0;
+        dy /= tex_size.y;
+        dy *= sign_y;
+        tc = vec2(texcoord.x, y_coord + dy);
+    }
+
+    vec3 colour = texture(Texture, tc).rgb;
+
+    if (u.enable_scanlines != 0) {
+        if (u.enable_gamma != 0) {
+            colour = pow(colour, vec3(u.input_gamma));
+        }
+        colour *= scan_line_weight * u.bloom_factor;
+        if (u.enable_gamma != 0) {
+            colour = pow(colour, vec3(1.0 / u.output_gamma));
+        }
+    }
+
+    // Máscara de fósforo
+    if (u.mask_type == 1) {
+        float which_mask = fract(gl_FragCoord.x * 0.5);
+        vec3 mask = (which_mask < 0.5)
+            ? vec3(u.mask_brightness, 1.0, u.mask_brightness)
+            : vec3(1.0, u.mask_brightness, 1.0);
+        colour *= mask;
+    } else if (u.mask_type == 2) {
+        float which_mask = fract(gl_FragCoord.x * 0.3333333);
+        vec3 mask = vec3(u.mask_brightness);
+        if (which_mask < 0.3333333)
+            mask.x = 1.0;
+        else if (which_mask < 0.6666666)
+            mask.y = 1.0;
+        else
+            mask.z = 1.0;
+        colour *= mask;
+    }
+
+    out_color = vec4(colour, 1.0);
+}

data/shaders/downscale.frag

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+#version 450
+layout(location = 0) in  vec2 v_uv;
+layout(location = 0) out vec4 out_color;
+
+layout(set = 2, binding = 0) uniform sampler2D source;
+
+layout(set = 3, binding = 0) uniform DownscaleUniforms {
+    int algorithm;  // 0 = Lanczos2 (ventana 2, ±2 taps), 1 = Lanczos3 (ventana 3, ±3 taps)
+    float pad0;
+    float pad1;
+    float pad2;
+} u;
+
+// Kernel Lanczos normalizado: sinc(t) * sinc(t/a) para |t| < a, 0 fuera.
+float lanczos(float t, float a) {
+    t = abs(t);
+    if (t < 0.0001) { return 1.0; }
+    if (t >= a) { return 0.0; }
+    const float PI = 3.14159265358979;
+    float pt = PI * t;
+    return (a * sin(pt) * sin(pt / a)) / (pt * pt);
+}
+
+void main() {
+    vec2 src_size = vec2(textureSize(source, 0));
+    // Posición en coordenadas de texel (centros de texel en N+0.5)
+    vec2 p = v_uv * src_size;
+    vec2 p_floor = floor(p);
+
+    float a = (u.algorithm == 0) ? 2.0 : 3.0;
+    int win = int(a);
+
+    vec4 color = vec4(0.0);
+    float weight_sum = 0.0;
+
+    for (int j = -win; j <= win; j++) {
+        for (int i = -win; i <= win; i++) {
+            // Centro del texel (i,j) relativo a p_floor
+            vec2 tap_center = p_floor + vec2(float(i), float(j)) + 0.5;
+            vec2 offset = tap_center - p;
+            float w = lanczos(offset.x, a) * lanczos(offset.y, a);
+            color += texture(source, tap_center / src_size) * w;
+            weight_sum += w;
+        }
+    }
+
+    out_color = (weight_sum > 0.0) ? (color / weight_sum) : vec4(0.0, 0.0, 0.0, 1.0);
+}

data/shaders/upscale.frag

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+#version 450
+
+// Vulkan GLSL fragment shader — Nearest-neighbour upscale pass
+// Used as the first render pass when supersampling is active.
+// Compile: glslc upscale.frag -o upscale.frag.spv
+//          xxd -i upscale.frag.spv > ../../source/core/rendering/sdl3gpu/upscale_frag_spv.h
+
+layout(location = 0) in  vec2 v_uv;
+layout(location = 0) out vec4 out_color;
+
+layout(set = 2, binding = 0) uniform sampler2D scene;
+
+void main() {
+    out_color = texture(scene, v_uv);
+}