Fix T99706: Crash rendering with headless builds

When rendering with headless builds, show an error instead of crashing.

Previously GPU_backend_init was called indirectly from
DRW_opengl_context_create, a new function is now called from the window
manager (GPU_backend_init_once), so it's possible to check if the GPU
has a back-end.

This also disables the `bgl` Python module when building WITH_HEADLESS.

Reviewed By: fclem

Ref D15463

8 files changed, 45 insertions, 7 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 33064864be6..c998919622e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -574,6 +574,10 @@ mark_as_advanced(
   WITH_GPU_BUILDTIME_SHADER_BUILDER
 )
 
+if(WITH_HEADLESS)
+  set(WITH_OPENGL OFF)
+endif()
+
 # Metal
 
 if (APPLE)
diff --git a/source/blender/gpu/CMakeLists.txt b/source/blender/gpu/CMakeLists.txt
index 0cb92e02515..774f2a0f312 100644
--- a/source/blender/gpu/CMakeLists.txt
+++ b/source/blender/gpu/CMakeLists.txt
@@ -5,7 +5,7 @@
 # to more easily highlight code-paths in other libraries that need to be refactored,
 # bf_gpu is allowed to have opengl regardless of this option.
 
-if(NOT WITH_OPENGL AND NOT WITH_METAL_BACKEND)
+if(NOT WITH_OPENGL AND NOT WITH_METAL_BACKEND AND NOT WITH_HEADLESS)
   add_definitions(-DWITH_OPENGL)
 endif()
 
diff --git a/source/blender/gpu/GPU_context.h b/source/blender/gpu/GPU_context.h
index 1fcd94c48fc..b04a4422baa 100644
--- a/source/blender/gpu/GPU_context.h
+++ b/source/blender/gpu/GPU_context.h
@@ -17,6 +17,7 @@
 extern "C" {
 #endif
 
+bool GPU_backend_init_once(void);
 void GPU_backend_init(eGPUBackendType backend);
 void GPU_backend_exit(void);
 bool GPU_backend_supported(eGPUBackendType type);
diff --git a/source/blender/gpu/intern/gpu_context.cc b/source/blender/gpu/intern/gpu_context.cc
index 4a0a9ecc7f6..d3b208dc6f6 100644
--- a/source/blender/gpu/intern/gpu_context.cc
+++ b/source/blender/gpu/intern/gpu_context.cc
@@ -85,10 +85,7 @@ Context *Context::get()
 
 GPUContext *GPU_context_create(void *ghost_window)
 {
-  if (GPUBackend::get() == nullptr) {
-    /* TODO: move where it make sense. */
-    GPU_backend_init(GPU_BACKEND_OPENGL);
-  }
+  GPU_backend_init_once();
 
   Context *ctx = GPUBackend::get()->context_alloc(ghost_window);
 
@@ -214,6 +211,18 @@ bool GPU_backend_supported(eGPUBackendType type)
   }
 }
 
+bool GPU_backend_init_once()
+{
+  if (GPUBackend::get() == nullptr) {
+    if (!GPU_backend_supported(GPU_BACKEND_OPENGL)) {
+      return false;
+    }
+    /* TODO: move where it make sense. */
+    GPU_backend_init(GPU_BACKEND_OPENGL);
+  }
+  return true;
+}
+
 void GPU_backend_init(eGPUBackendType backend_type)
 {
   BLI_assert(g_backend == nullptr);
diff --git a/source/blender/python/generic/CMakeLists.txt b/source/blender/python/generic/CMakeLists.txt
index 69bcfdfae4e..dfca528e758 100644
--- a/source/blender/python/generic/CMakeLists.txt
+++ b/source/blender/python/generic/CMakeLists.txt
@@ -17,7 +17,6 @@ set(INC_SYS
 )
 
 set(SRC
-  bgl.c
   bl_math_py_api.c
   blf_py_api.c
   bpy_threads.c
@@ -27,7 +26,6 @@ set(SRC
   py_capi_rna.c
   py_capi_utils.c
 
-  bgl.h
   bl_math_py_api.h
   blf_py_api.h
   idprop_py_api.h
@@ -40,6 +38,14 @@ set(SRC
   python_utildefines.h
 )
 
+if(WITH_OPENGL)
+  list(APPEND SRC
+    bgl.c
+
+    bgl.h
+  )
+endif()
+
 set(LIB
   ${GLEW_LIBRARY}
   ${PYTHON_LINKFLAGS}
diff --git a/source/blender/python/intern/bpy_interface.c b/source/blender/python/intern/bpy_interface.c
index 939fa475344..08dd5fe9cfc 100644
--- a/source/blender/python/intern/bpy_interface.c
+++ b/source/blender/python/intern/bpy_interface.c
@@ -259,7 +259,9 @@ static struct _inittab bpy_internal_modules[] = {
     {"mathutils.kdtree", PyInit_mathutils_kdtree},
 #endif
     {"_bpy_path", BPyInit__bpy_path},
+#ifdef WITH_OPENGL
     {"bgl", BPyInit_bgl},
+#endif
     {"blf", BPyInit_blf},
     {"bl_math", BPyInit_bl_math},
     {"imbuf", BPyInit_imbuf},
diff --git a/source/blender/render/intern/engine.c b/source/blender/render/intern/engine.c
index 8a4b4c2a70d..113af393706 100644
--- a/source/blender/render/intern/engine.c
+++ b/source/blender/render/intern/engine.c
@@ -46,6 +46,8 @@
 
 #include "DRW_engine.h"
 
+#include "GPU_context.h"
+
 #include "pipeline.h"
 #include "render_result.h"
 #include "render_types.h"
@@ -950,6 +952,16 @@ bool RE_engine_render(Render *re, bool do_all)
     re->draw_lock(re->dlh, true);
   }
 
+  if ((type->flag & RE_USE_GPU_CONTEXT) && (GPU_backend_get_type() == GPU_BACKEND_NONE)) {
+    /* Clear UI drawing locks. */
+    if (re->draw_lock) {
+      re->draw_lock(re->dlh, false);
+    }
+    BKE_report(re->reports, RPT_ERROR, "Can not initialize the GPU");
+    G.is_break = true;
+    return true;
+  }
+
   /* update animation here so any render layer animation is applied before
    * creating the render result */
   if ((re->r.scemode & (R_NO_FRAME_UPDATE | R_BUTS_PREVIEW)) == 0) {
diff --git a/source/blender/windowmanager/intern/wm_init_exit.c b/source/blender/windowmanager/intern/wm_init_exit.c
index 252cfc6e143..b9bb1d88819 100644
--- a/source/blender/windowmanager/intern/wm_init_exit.c
+++ b/source/blender/windowmanager/intern/wm_init_exit.c
@@ -169,6 +169,10 @@ void WM_init_opengl(void)
     wm_ghost_init(NULL);
   }
 
+  if (!GPU_backend_init_once()) {
+    return;
+  }
+
   /* Needs to be first to have an OpenGL context bound. */
   DRW_opengl_context_create();