ENH: wireframe: refine the rendering logic under paint

1. remove wireframe in 3d view, only keep in paint;
2. pass barycentric_coordinates from outside
3. add shortcut hints

Change-Id: I911e5cdf3475926d9527dc0839fdce072ed54746
(cherry picked from commit 6e16d0ccfb71741e55daabd757be9f9e7613e695)

resources/shaders/mm_gouraud_wireframe.vs

@@ -0,0 +1,43 @@
+#version 110
+
+const vec3 ZERO = vec3(0.0, 0.0, 0.0);
+
+attribute vec3 v_position;
+attribute vec3 v_barycentric;
+
+uniform mat4 volume_world_matrix;
+// Clipping plane, x = min z, y = max z. Used by the FFF and SLA previews to clip with a top / bottom plane.
+uniform vec2 z_range;
+// Clipping plane - general orientation. Used by the SLA gizmo.
+uniform vec4 clipping_plane;
+
+varying vec3 clipping_planes_dots;
+varying vec4 model_pos;
+
+varying vec3 barycentric_coordinates;
+
+struct SlopeDetection
+{
+    bool actived;
+	float normal_z;
+    mat3 volume_world_normal_matrix;
+};
+uniform SlopeDetection slope;
+void main()
+{
+    //model_pos = gl_Vertex;
+	model_pos = vec4(v_position, 1.0);
+    // Point in homogenous coordinates.
+    //vec4 world_pos = volume_world_matrix * gl_Vertex;
+	vec4 world_pos = volume_world_matrix * model_pos;
+
+    //gl_Position = ftransform();
+	gl_Position = gl_ModelViewProjectionMatrix * vec4(v_position.x, v_position.y, v_position.z, 1.0);
+    // Fill in the scalars for fragment shader clipping. Fragments with any of these components lower than zero are discarded.
+    clipping_planes_dots = vec3(dot(world_pos, clipping_plane), world_pos.z - z_range.x, z_range.y - world_pos.z);
+	
+    //compute the Barycentric Coordinates
+    //int vertexMod3 = gl_VertexID % 3;
+    //barycentric_coordinates = vec3(float(vertexMod3 == 0), float(vertexMod3 == 1), float(vertexMod3 == 2));
+	barycentric_coordinates = v_barycentric;
+}