Snap utilities: Avoid any OpenGL resources allocations for class members

OpenGL is not available in background mode, which was making unit tests to fail.
Additionally, it will cause some unwanted noise when someone renders his project
from command line, or performs any other command-line operation with Blender.

1 files changed, 31 insertions, 19 deletions

diff --git a/modules/snap_context/mesh_drawing.py b/modules/snap_context/mesh_drawing.py
index 82d87937..c85da506 100644
--- a/modules/snap_context/mesh_drawing.py
+++ b/modules/snap_context/mesh_drawing.py
@@ -156,33 +156,43 @@ class _Mesh_Arrays():
 
 
 class GPU_Indices_Mesh():
-    shader = Shader(
-        load_shader('3D_vert.glsl'),
-        None,
-        load_shader('primitive_id_frag.glsl'),
-    )
+    shader = None
 
-    unif_use_clip_planes = bgl.glGetUniformLocation(shader.program, 'use_clip_planes')
-    unif_clip_plane = bgl.glGetUniformLocation(shader.program, 'clip_plane')
+    @classmethod
+    def init_opengl(cls):
+        # OpenGL was already initialized, nothing to do here.
+        if cls.shader is not None:
+            return
+
+        cls.shader = Shader(
+            load_shader('3D_vert.glsl'),
+            None,
+            load_shader('primitive_id_frag.glsl'),
+        )
 
-    unif_MVP = bgl.glGetUniformLocation(shader.program, 'MVP')
-    unif_MV = bgl.glGetUniformLocation(shader.program, 'MV')
-    unif_offset = bgl.glGetUniformLocation(shader.program, 'offset')
+        cls.unif_use_clip_planes = bgl.glGetUniformLocation(cls.shader.program, 'use_clip_planes')
+        cls.unif_clip_plane = bgl.glGetUniformLocation(cls.shader.program, 'clip_plane')
 
-    attr_pos = bgl.glGetAttribLocation(shader.program, 'pos')
-    attr_primitive_id = bgl.glGetAttribLocation(shader.program, 'primitive_id')
+        cls.unif_MVP = bgl.glGetUniformLocation(cls.shader.program, 'MVP')
+        cls.unif_MV = bgl.glGetUniformLocation(cls.shader.program, 'MV')
+        cls.unif_offset = bgl.glGetUniformLocation(cls.shader.program, 'offset')
 
-    P = bgl.Buffer(bgl.GL_FLOAT, (4, 4))
-    MV = bgl.Buffer(bgl.GL_FLOAT, (4, 4))
+        cls.attr_pos = bgl.glGetAttribLocation(cls.shader.program, 'pos')
+        cls.attr_primitive_id = bgl.glGetAttribLocation(cls.shader.program, 'primitive_id')
 
-    # returns of public API #
-    vert_index = bgl.Buffer(bgl.GL_INT, 1)
+        cls.P = bgl.Buffer(bgl.GL_FLOAT, (4, 4))
+        cls.MV = bgl.Buffer(bgl.GL_FLOAT, (4, 4))
 
-    tri_co = bgl.Buffer(bgl.GL_FLOAT, (3, 3))
-    edge_co = bgl.Buffer(bgl.GL_FLOAT, (2, 3))
-    vert_co = bgl.Buffer(bgl.GL_FLOAT, 3)
+        # returns of public API #
+        cls.vert_index = bgl.Buffer(bgl.GL_INT, 1)
+
+        cls.tri_co = bgl.Buffer(bgl.GL_FLOAT, (3, 3))
+        cls.edge_co = bgl.Buffer(bgl.GL_FLOAT, (2, 3))
+        cls.vert_co = bgl.Buffer(bgl.GL_FLOAT, 3)
 
     def __init__(self, obj, draw_tris, draw_edges, draw_verts):
+        GPU_Indices_Mesh.init_opengl()
+
         self._NULL = gl_buffer_void_as_long(0)
 
         self.MVP = bgl.Buffer(bgl.GL_FLOAT, (4, 4))
@@ -463,6 +473,7 @@ def _restore_shader_state(cls):
 def gpu_Indices_enable_state():
     _store_current_shader_state(PreviousGLState)
 
+    GPU_Indices_Mesh.init_opengl()
     bgl.glUseProgram(GPU_Indices_Mesh.shader.program)
     #bgl.glBindVertexArray(GPU_Indices_Mesh.vao[0])
 
@@ -477,6 +488,7 @@ def gpu_Indices_use_clip_planes(rv3d, value):
         planes = bgl.Buffer(bgl.GL_FLOAT, (6, 4), rv3d.clip_planes)
 
         _store_current_shader_state(PreviousGLState)
+        GPU_Indices_Mesh.init_opengl()
         bgl.glUseProgram(GPU_Indices_Mesh.shader.program)
         bgl.glUniform1i(GPU_Indices_Mesh.unif_use_clip_planes, value)