Extract draw merge final composite gate helper

src/canvas.cpp

@@ -508,6 +508,12 @@ static void execute_canvas_draw_merge_final_plane_composite(
     pp::panopainter::execute_legacy_canvas_draw_merge_final_plane_composite(uniforms, execution);
 }
 
+static void execute_canvas_draw_merge_plane_final_composite(
+    Canvas& canvas,
+    const glm::mat4& ortho,
+    bool draw_checkerboard,
+    bool use_blend);
+
 static void execute_canvas_draw_merge_plane_iteration(
     Canvas& canvas,
     const std::array<bool, 6>& faces,
@@ -561,15 +567,23 @@ static void execute_canvas_draw_merge_plane_iteration(
                 draw_checkerboard);
         }
 
-        if (use_blend)
-        {
-            canvas.draw_merge_final_plane_composite(ortho, draw_checkerboard);
-        }
-
+        execute_canvas_draw_merge_plane_final_composite(canvas, ortho, draw_checkerboard, use_blend);
         canvas.m_layers_merge.rtt(plane_index).unbindFramebuffer();
     }
 }
 
+static void execute_canvas_draw_merge_plane_final_composite(
+    Canvas& canvas,
+    const glm::mat4& ortho,
+    bool draw_checkerboard,
+    bool use_blend)
+{
+    if (use_blend)
+    {
+        canvas.draw_merge_final_plane_composite(ortho, draw_checkerboard);
+    }
+}
+
 static auto make_canvas_stroke_mix_pass_shell(
     Canvas& canvas,
     const glm::vec2& bb_min,