fix a confusing issue around '#if' vs '#ifdef' conditional compilatio…

…n in shaders (fixes #118)
floooh · Feb 12, 2024 · 6362c8f · 6362c8f
1 parent 06a8956
commit 6362c8f
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,6 +1,24 @@
 CHANGELOG
 =========
 
+#### **12-Feb-2024**
+
+Fixed a confusing behaviour when writing conditional shader code via
+`#if` vs `#ifdef`. Previously, when a shader is compiled it would get
+an implicit definition block at the start looking like this:
+
+```
+#define SOKOL_GLSL (1)
+#define SOKOL_HLSL (0)
+#define SOKOL_MSL (0)
+#define SOKOL_WGSL (0)
+```
+
+...meaning an `#ifdef` would always trigger and only `#if` had worked.
+
+Now only the define for the current output language is present, so that
+both `#if` and `#ifdef` works.
+
 #### **29-Oct-2023**
 
 Fix a reflection parsing regression that was introduced in the last

diff --git a/src/shdc/spirv.cc b/src/shdc/spirv.cc
@@ -27,10 +27,18 @@ extern const TBuiltInResource DefaultTBuiltInResource;
 /* merge shader snippet source into a single string */
 static std::string merge_source(const input_t& inp, const snippet_t& snippet, slang_t::type_t slang, const std::vector<std::string>& defines) {
     std::string src = "#version 450\n";
-    src += fmt::format("#define SOKOL_GLSL ({})\n", slang_t::is_glsl(slang) ? 1 : 0);
-    src += fmt::format("#define SOKOL_HLSL ({})\n", slang_t::is_hlsl(slang) ? 1 : 0);
-    src += fmt::format("#define SOKOL_MSL ({})\n", slang_t::is_msl(slang) ? 1 : 0);
-    src += fmt::format("#define SOKOL_WGSL ({})\n", slang_t::is_wgsl(slang) ? 1 : 0);
+    if (slang_t::is_glsl(slang)) {
+        src += "#define SOKOL_GLSL (1)\n";
+    }
+    if (slang_t::is_hlsl(slang)) {
+        src += "#define SOKOL_HLSL (1)\n";
+    }
+    if (slang_t::is_msl(slang)) {
+        src += "#define SOKOL_MSL (1)\n";
+    }
+    if (slang_t::is_wgsl(slang)) {
+        src += "#define SOKOL_WGSL (1)\n";
+    }
     for (const std::string& define : defines) {
         src += fmt::format("#define {} (1)\n", define);
     }

diff --git a/test/sapp/primtypes-sapp.glsl b/test/sapp/primtypes-sapp.glsl
@@ -12,7 +12,10 @@ out vec4 color;
 
 void main() {
     gl_Position = mvp * vec4(position.xy, 0, 1);
+    // WebGPU doesn't support point size
+    #ifndef SOKOL_WGSL
     gl_PointSize = point_size;
+    #endif
     color = color0;
 }
 @end
@@ -26,4 +29,3 @@ void main() {
 @end
 
 @program primtypes vs fs
-