Fix 1px of warped main image shining through the composite mesh at hi…

…gher resolutions.

Now we don't add the half texel offset to the vertex coordinates, but to the calculated u/v, which will prevent the texture wrapping (happens mostly with "nearest" interpolation lookups) mentioned in Milkdrop's code from happening, but make the mesh exactly fill the screen.

src/libprojectM/MilkdropPreset/FinalComposite.cpp

@@ -156,13 +156,13 @@ void FinalComposite::InitializeMesh(const PresetState& presetState)
     {
         int const gridY2 = gridY - gridY / (compositeGridHeight / 2);
         float const v = SquishToCenter(gridY2 * dividedByY, 3.0f);
-        float const sy = -((v - halfTexelHeight) * 2.0f - 1.0f);
+        float const sy = -(v * 2.0f - 1.0f);
 
         for (int gridX = 0; gridX < compositeGridWidth; gridX++)
         {
             int const gridX2 = gridX - gridX / (compositeGridWidth / 2);
             float const u = SquishToCenter(gridX2 * dividedByX, 3.0f);
-            float const sx = (u - halfTexelWidth) * 2.0f - 1.0f;
+            float const sx = u * 2.0f - 1.0f;
 
             auto& vertex = m_vertices.at(gridX + gridY * compositeGridWidth);
 
@@ -236,8 +236,8 @@ void FinalComposite::InitializeMesh(const PresetState& presetState)
                     ang = PI * 0.0f;
                 }
             }
-            vertex.u = u;
-            vertex.v = v;
+            vertex.u = u + halfTexelWidth;
+            vertex.v = v + halfTexelHeight;
 
             vertex.radius = rad;
             vertex.angle = ang;