Applies To:
  • CitectSCADA 1.00, 1.01, 1.10, 1.11, 1.20, 2.00, 2.01

If the boundaries of two symbols overlap, you may get a mixture of the symbols at the intersection region when these symbols are updated.

What is happening is as follows: Just before Citect draws a symbol onto the screen, it saves the background under the symbol. Citect will save a rectangular region that encloses the entire symbol. If the symbol is a circle of size 50 pixel's, Citect will save a 50 by 50 square of the background. Citect then draws the symbol (on the background). When the symbol is removed, Citect will copy the background image it saved back to the screen - in this case the 50 by 50 square. If there is other animation that was outside the circle but inside the bounding square, it will be overwritten when the symbol is updated.

If you use DspSym() function to display the symbol, you can set the display mode. Mode 0 will display the symbol as described above. If you display in mode 1, Citect will not save the screen under the symbol and will not restore the screen when the symbol is erased. Using this mode will not overwrite other animation in the bounding region, however each symbol should fully cover the existing symbol displayed because the current symbol is not erased. 

You may get around this effect by not placing other animation objects within the bounding rectangle of a symbol or by using the non erase draw mode of DspSym(), ie mode 1.

In Version 2.01 an enhancement has been implemented that provides an alternative restoration to the background image after a symbol is deleted. The background image is now restored only under the symbol. If the symbol is a 50 pixel circle, any animation in the boundary region - but outside of the circle - is not over written. This operation is slower than restoring the display in the previous version. This display mode is controlled by the parameter [ANIMATOR] SymbolOverlap. This parameter is 0 by default to be compatible with pervious version, so to allow overlapping symbols, set the parameter to 1.