STM32F4HAL::getTFTCurrentLine() method

@fn virtual uint16_t getTFTCurrentLine() Get the current line (Y) of the TFT controller This function is used to obtain the progress of the TFT (LTDC) controller. More specifically, the line (or Y-value) currently being transferred. Note: The value must be adjusted to account for vertical back porch before returning, such that the value is always within the range of 0 <= value < actual display height in pixels It is used for the REFRESH_STRATEGY_OPTIM_SINGLE_BUFFER_TFT_CTRL frame refresh strategy in order to synchronize frame buffer drawing with TFT controller progress. If this strategy is used, the concrete HAL subclass must provide an override of this function that returns correct line value. If this strategy is not used, then the getTFTCurrentLine function is never called and can be disregarded.