glgsg: Fix sharing shaders between GSGs

Fixes #1728

panda/src/glstuff/glCgShaderContext_src.cxx

@@ -388,14 +388,17 @@ valid() {
  * all of the shader's input parameters.
  */
 void CLP(CgShaderContext)::
-bind() {
+bind(GraphicsStateGuardian *gsg) {
+  CLP(GraphicsStateGuardian) *glgsg = (CLP(GraphicsStateGuardian) *)gsg;
+  _glgsg = glgsg;
+
   if (_cg_program != 0) {
     // Bind the shaders.
     cgGLEnableProgramProfiles(_cg_program);
     cgGLBindProgram(_cg_program);
 
     cg_report_errors();
-    _glgsg->report_my_gl_errors();
+    glgsg->report_my_gl_errors();
   }
 }
 

panda/src/glstuff/glCgShaderContext_src.h

@@ -34,7 +34,7 @@ public:
   ALLOC_DELETED_CHAIN(CLP(CgShaderContext));
 
   bool valid(void) override;
-  void bind() override;
+  void bind(GraphicsStateGuardian *gsg) override;
   void unbind() override;
 
   void set_state_and_transform(const RenderState *state,

panda/src/glstuff/glGraphicsStateGuardian_src.cxx

@@ -8717,7 +8717,7 @@ do_issue_shader() {
         // If it's a different type of shader, make sure to unbind the old.
         _current_shader_context->unbind();
       }
-      context->bind();
+      context->bind(this);
       _current_shader = shader;
     }
 

panda/src/glstuff/glShaderContext_src.cxx

@@ -416,7 +416,7 @@ CLP(ShaderContext)(CLP(GraphicsStateGuardian) *glgsg, Shader *s) : ShaderContext
   if (_glgsg->_current_shader_context == nullptr) {
     _glgsg->_glUseProgram(0);
   } else {
-    _glgsg->_current_shader_context->bind();
+    _glgsg->_current_shader_context->bind(_glgsg);
   }
 
   _mat_part_cache = new LVecBase4f[_shader->cp_get_mat_cache_size()];
@@ -2192,15 +2192,18 @@ valid() {
  * all of the shader's input parameters.
  */
 void CLP(ShaderContext)::
-bind() {
+bind(GraphicsStateGuardian *gsg) {
+  CLP(GraphicsStateGuardian) *glgsg = (CLP(GraphicsStateGuardian) *)gsg;
+  _glgsg = glgsg;
+
   if (!_validated) {
-    _glgsg->_glValidateProgram(_glsl_program);
+    glgsg->_glValidateProgram(_glsl_program);
     glsl_report_program_errors(_glsl_program, false);
     _validated = true;
   }
 
   if (!_shader->get_error_flag()) {
-    _glgsg->_glUseProgram(_glsl_program);
+    glgsg->_glUseProgram(_glsl_program);
   }
 
   if (GLCAT.is_spam()) {
@@ -2208,7 +2211,7 @@ bind() {
                  << _shader->get_filename() << "\n";
   }
 
-  _glgsg->report_my_gl_errors();
+  glgsg->report_my_gl_errors();
 }
 
 /**

panda/src/glstuff/glShaderContext_src.h

@@ -42,7 +42,7 @@ public:
   bool get_sampler_texture_type(int &out, GLenum param_type);
 
   bool valid(void) override;
-  void bind() override;
+  void bind(GraphicsStateGuardian *gsg) override;
   void unbind() override;
 
   void set_state_and_transform(const RenderState *state,

panda/src/gobj/shaderContext.h

@@ -19,6 +19,8 @@
 #include "savedContext.h"
 #include "shader.h"
 
+class GraphicsStateGuardian;
+
 /**
  * The ShaderContext is meant to contain the compiled version of a shader
  * string.  ShaderContext is an abstract base class, there will be a subclass
@@ -38,7 +40,7 @@ public:
                                        const TransformState *) {};
 
   INLINE virtual bool valid() { return false; }
-  INLINE virtual void bind() {};
+  INLINE virtual void bind(GraphicsStateGuardian *gsg) {};
   INLINE virtual void unbind() {};
   INLINE virtual void issue_parameters(int altered) {};
   INLINE virtual void disable_shader_vertex_arrays() {};