Use special purpose shader for borders

yt_idv/scene_components/base_component.py

@@ -228,7 +228,7 @@ def _final_pass_vertex_default(self):
 
     @traitlets.default("final_pass_fragment")
     def _final_pass_fragment_default(self):
-        return "passthrough"
+        return "display_border"
 
     @traitlets.default("base_quad")
     def _default_base_quad(self):

yt_idv/shaders/display_border.frag.glsl

@@ -0,0 +1,13 @@
+in vec2 UV;
+
+out vec4 color;
+
+void main(){
+   color = texture(fb_tex, UV);
+   color.a = 1.0;
+   vec2 d = abs(UV - vec2(0.5));
+   if(0.5 - max(d.x, d.y) < draw_boundary) {
+      color = vec4(1.0, 1.0, 1.0, 0.5);
+   }
+   gl_FragDepth = texture(db_tex, UV).r;
+}

yt_idv/shaders/passthrough.frag.glsl

@@ -5,9 +5,5 @@ out vec4 color;
 void main(){
    color = texture(fb_tex, UV);
    color.a = 1.0;
-   vec2 d = abs(UV - vec2(0.5));
-   if(0.5 - max(d.x, d.y) < draw_boundary) {
-      color = vec4(1.0, 1.0, 1.0, 0.5);
-   }
    gl_FragDepth = texture(db_tex, UV).r;
 }