From 6075307e66fa03cc7dbfe5979d2cedd08525219a Mon Sep 17 00:00:00 2001
From: rdb <git@rdb.name>
Date: Fri, 3 Feb 2023 15:17:55 +0100
Subject: [PATCH] glgsg: Set maximum vertex attrib stride for WebGL

---
 panda/src/glstuff/glGraphicsStateGuardian_src.I   | 5 ++++-
 panda/src/glstuff/glGraphicsStateGuardian_src.cxx | 2 +-
 panda/src/glstuff/glGraphicsStateGuardian_src.h   | 4 ++++
 3 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/panda/src/glstuff/glGraphicsStateGuardian_src.I b/panda/src/glstuff/glGraphicsStateGuardian_src.I
index 216c16f259..9571762b6f 100644
--- a/panda/src/glstuff/glGraphicsStateGuardian_src.I
+++ b/panda/src/glstuff/glGraphicsStateGuardian_src.I
@@ -186,7 +186,10 @@ has_fixed_function_pipeline() const {
  */
 INLINE int CLP(GraphicsStateGuardian)::
 get_max_vertex_attrib_stride() const {
-#ifdef OPENGLES_1
+#ifdef __EMSCRIPTEN__
+  // WebGL has a static limit of 255 (yeah, that low).
+  return 255;
+#elif defined(OPENGLES_1)
   // Best guess.
   return 2048;
 #else
diff --git a/panda/src/glstuff/glGraphicsStateGuardian_src.cxx b/panda/src/glstuff/glGraphicsStateGuardian_src.cxx
index 4c578190e7..ce65d2eee1 100644
--- a/panda/src/glstuff/glGraphicsStateGuardian_src.cxx
+++ b/panda/src/glstuff/glGraphicsStateGuardian_src.cxx
@@ -3522,7 +3522,7 @@ reset() {
   }
 #endif
 
-#ifndef OPENGLES_1
+#if !defined(OPENGLES_1) && !defined(__EMSCRIPTEN__)
   _max_vertex_attrib_stride = -1;
 #ifdef OPENGLES
   if (is_at_least_gles_version(3, 1))
diff --git a/panda/src/glstuff/glGraphicsStateGuardian_src.h b/panda/src/glstuff/glGraphicsStateGuardian_src.h
index 71842f68ed..15b7b8fbe5 100644
--- a/panda/src/glstuff/glGraphicsStateGuardian_src.h
+++ b/panda/src/glstuff/glGraphicsStateGuardian_src.h
@@ -753,7 +753,11 @@ protected:
   bool _use_vertex_attrib_binding;
   CPT(GeomVertexFormat) _current_vertex_format;
   const GeomVertexColumn *_vertex_attrib_columns[32];
+#ifdef __EMSCRIPTEN__
+  static const int _max_vertex_attrib_stride = 255;
+#else
   int _max_vertex_attrib_stride = INT_MAX;
+#endif
 
   GLuint _current_sbuffer_index;
   pvector<GLuint> _current_sbuffer_base;