Thin canvas draw seams and own grid worker

src/legacy_canvas_draw_merge_services.h

@@ -203,6 +203,15 @@ struct LegacyCanvasDrawMergeDisplayResolveExecution {
     std::function<void()> unbind_resolve_texture;
 };
 
+struct LegacyCanvasDrawMergePostDrawExecution {
+    std::function<void()> draw_mask_free;
+    std::function<void()> draw_mask_line;
+    std::function<void()> draw_smask_faces;
+    std::function<void()> draw_grid_modes;
+    std::function<void()> draw_heightmap;
+    std::function<void()> draw_current_modes;
+};
+
 [[nodiscard]] inline LegacyCanvasDrawMergeShaderExecution legacy_shader_manager_draw_merge_execution() noexcept
 {
     return {
@@ -492,4 +501,31 @@ inline void execute_legacy_canvas_draw_merge_display_resolve(
     execution.unbind_resolve_texture();
 }
 
+inline void execute_legacy_canvas_draw_merge_post_draw(
+    bool smask_active,
+    bool draw_mask_overlay,
+    int smask_mode,
+    bool draw_grid_modes,
+    const LegacyCanvasDrawMergePostDrawExecution& execution)
+{
+    if (smask_active || draw_mask_overlay) {
+        if (smask_mode == 1) {
+            execution.draw_mask_free();
+        } else if (smask_mode == 2) {
+            execution.draw_mask_line();
+        }
+    }
+
+    if (smask_active) {
+        execution.draw_smask_faces();
+    }
+
+    if (draw_grid_modes) {
+        execution.draw_grid_modes();
+    }
+
+    execution.draw_heightmap();
+    execution.draw_current_modes();
+}
+
 } // namespace pp::panopainter