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

1 files changed, 12 insertions, 0 deletions

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) {