Fix grid draw, circle draw, most editor drawing

source/shaders/gridfrag.glsl

@@ -1,7 +1,7 @@
 #version 330
 out vec4 frag_color;
 
-in vec2 apos;
+in vec2 apos; /* Drawing coordinates of the grid */
 
 uniform float thickness; /* thickness in pixels */
 uniform float span;

source/shaders/gridvert.glsl

@@ -13,6 +13,7 @@ void main()
 {
 //    vec4 ipos = inverse(projection) * vec4(pos, 0.f, 1.f);
     apos = pos * vec2(600, 360);
+    apos += offset;
 //    apos = pos + offset;