Improve preprocessor to allow for define value injection (#7309)

* Improve preprocessor to allow for define value injection

* lint

* using it for the skybox shader

---------

Co-authored-by: Martin Valigursky <[email protected]>

src/core/preprocessor.js

@@ -102,6 +102,14 @@ class Preprocessor {
             }
         });
 
+        // extract defines with name starting with __INJECT_
+        const injectDefines = new Map();
+        defines.forEach((value, key) => {
+            if (key.startsWith('__INJECT_')) {
+                injectDefines.set(key, value);
+            }
+        });
+
         // strip comments again after the includes have been resolved
         source = this.stripComments(source);
 
@@ -111,6 +119,9 @@ class Preprocessor {
         // process array sizes
         source = this.processArraySize(source, intDefines);
 
+        // inject defines
+        source = this.injectDefines(source, injectDefines);
+
         return source;
     }
 
@@ -131,6 +142,28 @@ class Preprocessor {
         return source;
     }
 
+    static injectDefines(source, injectDefines) {
+
+        if (source !== null && injectDefines.size > 0) {
+
+            // replace all instances of the injected defines with the value itself
+            const lines = source.split('\n');
+            injectDefines.forEach((value, key) => {
+                const regex = new RegExp(`\\b${key}\\b`, 'g');
+                for (let i = 0; i < lines.length; i++) {
+
+                    // replace them on lines that do not contain a preprocessor directive (the define itself for example)
+                    if (!lines[i].includes('#')) {
+                        lines[i] = lines[i].replace(regex, value);
+                    }
+                }
+            });
+            source = lines.join('\n');
+        }
+
+        return source;
+    }
+
     static RemoveEmptyLines(source) {
 
         if (source !== null) {

src/scene/shader-lib/chunks/skybox/frag/skybox.js

@@ -41,14 +41,14 @@ export default /* glsl */`
             #endif
 
             dir.x *= -1.0;
-            vec3 linear = SKYBOX_DECODE_FNC(textureCube(texture_cubeMap, dir));
+            vec3 linear = __INJECT_SKYBOX_DECODE_FNC(textureCube(texture_cubeMap, dir));
 
         #else // env-atlas
 
             vec3 dir = vViewDir * vec3(-1.0, 1.0, 1.0);
             vec2 uv = toSphericalUv(normalize(dir));
 
-            vec3 linear = SKYBOX_DECODE_FNC(texture2D(texture_envAtlas, mapRoughnessUv(uv, mipLevel)));
+            vec3 linear = __INJECT_SKYBOX_DECODE_FNC(texture2D(texture_envAtlas, mapRoughnessUv(uv, mipLevel)));
 
         #endif
 

src/scene/skybox/sky-mesh.js

@@ -43,7 +43,7 @@ class SkyMesh {
         });
 
         // defines
-        material.setDefine('SKYBOX_DECODE_FNC', ChunkUtils.decodeFunc(texture.encoding));
+        material.setDefine('__INJECT_SKYBOX_DECODE_FNC', ChunkUtils.decodeFunc(texture.encoding));
         if (type !== SKYTYPE_INFINITE) material.setDefine('SKYMESH', '');
         if (texture.cubemap) material.setDefine('SKY_CUBEMAP', '');
 

test/core/preprocessor.test.mjs

@@ -16,6 +16,8 @@ describe('Preprocessor', function () {
 
     const srcData = `
         
+        #define __INJECT_COUNT 2
+        #define __INJECT_STRING hello
         #define FEATURE1
         #define FEATURE2
 
@@ -95,6 +97,9 @@ describe('Preprocessor', function () {
         #if NAME != hello
             CMP5
         #endif
+
+        TESTINJECTION __INJECT_COUNT
+        INJECTSTRING __INJECT_STRING(x)
     `;
 
     it('returns false for MORPH_A', function () {
@@ -201,4 +206,12 @@ describe('Preprocessor', function () {
         expect(Preprocessor.run(srcData, includes, { stripDefines: true }).includes('#')).to.equal(false);
     });
 
+    it('returns true for working integer injection', function () {
+        expect(Preprocessor.run(srcData, includes).includes('TESTINJECTION 2')).to.equal(true);
+    });
+
+    it('returns true for working string injection', function () {
+        expect(Preprocessor.run(srcData, includes).includes('INJECTSTRING hello(x)')).to.equal(true);
+    });
+
 });