Define dynamically the fragment shader

src/main.rs

@@ -65,6 +65,51 @@ fn main() {
         glium::texture::SrgbTexture2d::new(&display, image).unwrap()
     });
 
+    let mut uniform_sampler_2d_str: String = "".to_string();
+    for i in 1..BIOMES_NUMBER {
+        uniform_sampler_2d_str += &format!(", tex{}", i);
+    }
+
+    let mut switch_v_biome_str: String = "".to_string();
+    for i in 0..BIOMES_NUMBER {
+        switch_v_biome_str += &format!(
+            "
+        case {}u:
+            f_color = texture(tex{}, v_tex_coords);
+        break;
+        ",
+            i, i
+        );
+    }
+    switch_v_biome_str += &format!(
+        "
+    default: // case {}u:
+        f_color = texture(tex{}, v_tex_coords);
+    ",
+        BIOMES_NUMBER - 1,
+        BIOMES_NUMBER - 1
+    );
+
+    let fragment = &format!(
+        "
+                #version 140
+
+                in vec2 v_tex_coords;
+                flat in uint v_biome;
+
+                out vec4 f_color;
+
+                uniform sampler2D tex0{};
+
+                void main() {{
+                    switch (v_biome) {{
+                        {}
+                    }}
+                }}
+            ",
+        uniform_sampler_2d_str, switch_v_biome_str
+    );
+
     // the program
     let program = program!(&display,
         140 => {
@@ -119,77 +164,7 @@ fn main() {
                 }
             ",
 
-            fragment: "
+            fragment: fragment,
-                #version 140
-
-                in vec2 v_tex_coords;
-                flat in uint v_biome;
-
-                out vec4 f_color;
-
-                uniform sampler2D tex0, tex1, tex2, tex3, tex4, tex5, tex6, tex7, tex8, tex9, tex10, tex11, tex12, tex13, tex14, tex15, tex16, tex17, tex18;
-
-                void main() {
-                    switch (v_biome) {
-                        case 0u:
-                            f_color = texture(tex0, v_tex_coords);
-                            break;
-                        case 1u:
-                            f_color = texture(tex1, v_tex_coords);
-                            break;
-                        case 2u:
-                            f_color = texture(tex2, v_tex_coords);
-                            break;
-                        case 3u:
-                            f_color = texture(tex3, v_tex_coords);
-                            break;
-                        case 4u:
-                            f_color = texture(tex4, v_tex_coords);
-                            break;
-                        case 5u:
-                            f_color = texture(tex5, v_tex_coords);
-                            break;
-                        case 6u:
-                            f_color = texture(tex6, v_tex_coords);
-                            break;
-                        case 7u:
-                            f_color = texture(tex7, v_tex_coords);
-                            break;
-                        case 8u:
-                            f_color = texture(tex8, v_tex_coords);
-                            break;
-                        case 9u:
-                            f_color = texture(tex9, v_tex_coords);
-                            break;
-                        case 10u:
-                            f_color = texture(tex10, v_tex_coords);
-                            break;
-                        case 11u:
-                            f_color = texture(tex11, v_tex_coords);
-                            break;
-                        case 12u:
-                            f_color = texture(tex12, v_tex_coords);
-                            break;
-                        case 13u:
-                            f_color = texture(tex13, v_tex_coords);
-                            break;
-                        case 14u:
-                            f_color = texture(tex14, v_tex_coords);
-                            break;
-                        case 15u:
-                            f_color = texture(tex15, v_tex_coords);
-                            break;
-                        case 16u:
-                            f_color = texture(tex16, v_tex_coords);
-                            break;
-                        case 17u:
-                            f_color = texture(tex17, v_tex_coords);
-                            break;
-                        default: // case 18u:
-                            f_color = texture(tex18, v_tex_coords);
-                    }
-                }
-            "
         },
     )
     .unwrap();