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Display.cpp
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Display.cpp
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/*
* © 2021, Chris Harlow, Neil McKechnie. All rights reserved.
*
* This file is part of CommandStation-EX
*
* This is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* It is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with CommandStation. If not, see <https://www.gnu.org/licenses/>.
*/
// CAUTION: the device dependent parts of this class are created in the .ini
// using LCD_Implementation.h
/* The strategy for drawing the screen is as follows.
* 1) There are up to eight rows of text to be displayed.
* 2) Blank rows of text are ignored.
* 3) If there are more non-blank rows than screen lines,
* then all of the rows are displayed, with the rest of the
* screen being blank.
* 4) If there are fewer non-blank rows than screen lines,
* then a scrolling strategy is adopted so that, on each screen
* refresh, a different subset of the rows is presented.
* 5) On each entry into loop2(), a single operation is sent to the
* screen; this may be a position command or a character for
* display. This spreads the onerous work of updating the screen
* and ensures that other loop() functions in the application are
* not held up significantly. The exception to this is when
* the loop2() function is called with force=true, where
* a screen update is executed to completion. This is normally
* only done during start-up.
* The scroll mode is selected by defining SCROLLMODE as 0, 1 or 2
* in the config.h.
* #define SCROLLMODE 0 is scroll continuous (fill screen if poss),
* #define SCROLLMODE 1 is by page (alternate between pages),
* #define SCROLLMODE 2 is by row (move up 1 row at a time).
*/
#include "Display.h"
// Constructor - allocates device driver.
Display::Display(DisplayDevice *deviceDriver) {
_deviceDriver = deviceDriver;
// Get device dimensions in characters (e.g. 16x2).
numScreenColumns = _deviceDriver->getNumCols();
numScreenRows = _deviceDriver->getNumRows();
for (uint8_t row = 0; row < MAX_CHARACTER_ROWS; row++)
rowBuffer[row][0] = '\0';
addDisplay(0); // Add this display as display number 0
};
void Display::begin() {
_deviceDriver->begin();
_deviceDriver->clearNative();
}
void Display::_clear() {
_deviceDriver->clearNative();
for (uint8_t row = 0; row < MAX_CHARACTER_ROWS; row++)
rowBuffer[row][0] = '\0';
}
void Display::_setRow(uint8_t line) {
hotRow = line;
hotCol = 0;
rowBuffer[hotRow][0] = '\0'; // Clear existing text
}
size_t Display::_write(uint8_t b) {
if (hotRow >= MAX_CHARACTER_ROWS || hotCol >= MAX_CHARACTER_COLS) return -1;
rowBuffer[hotRow][hotCol] = b;
hotCol++;
rowBuffer[hotRow][hotCol] = '\0';
return 1;
}
// Refresh screen completely (will block until complete). Used
// during start-up.
void Display::_refresh() {
loop2(true);
}
// On normal loop entries, loop will only make one output request on each
// entry, to avoid blocking while waiting for the I2C.
void Display::_displayLoop() {
// If output device is busy, don't do anything on this loop
// This avoids blocking while waiting for the device to complete.
if (!_deviceDriver->isBusy()) loop2(false);
}
Display *Display::loop2(bool force) {
unsigned long currentMillis = millis();
if (!force) {
// See if we're in the time between updates
if ((currentMillis - lastScrollTime) < DISPLAY_SCROLL_TIME)
return NULL;
} else {
// force full screen update from the beginning.
rowFirst = 0;
rowCurrent = 0;
bufferPointer = 0;
noMoreRowsToDisplay = false;
slot = 0;
}
do {
if (bufferPointer == 0) {
// Search for non-blank row
while (!noMoreRowsToDisplay) {
if (!isCurrentRowBlank()) break;
moveToNextRow();
if (rowCurrent == rowFirst) noMoreRowsToDisplay = true;
}
if (noMoreRowsToDisplay) {
// No non-blank lines left, so draw blank line
buffer[0] = '\0';
} else {
// Non-blank line found, so copy it (including terminator)
for (uint8_t i = 0; i <= MAX_CHARACTER_COLS; i++)
buffer[i] = rowBuffer[rowCurrent][i];
}
_deviceDriver->setRowNative(slot); // Set position for display
charIndex = 0;
bufferPointer = &buffer[0];
} else {
// Write next character, or a space to erase current position.
char ch = *bufferPointer;
if (ch) {
_deviceDriver->writeNative(ch);
bufferPointer++;
} else {
_deviceDriver->writeNative(' ');
}
if (++charIndex >= MAX_CHARACTER_COLS) {
// Screen slot completed, move to next nonblank row
bufferPointer = 0;
for (;;) {
moveToNextRow();
if (rowCurrent == rowFirst) {
noMoreRowsToDisplay = true;
break;
}
if (!isCurrentRowBlank()) break;
}
// Move to next screen slot, if available
slot++;
if (slot >= numScreenRows) {
// Last slot on screen written, so get ready for next screen update.
#if SCROLLMODE==0
// Scrollmode 0 scrolls continuously. If the rows fit on the screen,
// then restart at row 0, but otherwise continue with the row
// after the last one displayed.
if (countNonBlankRows() <= numScreenRows)
rowCurrent = 0;
rowFirst = rowCurrent;
#elif SCROLLMODE==1
// Scrollmode 1 scrolls by page, so if the last page has just completed then
// next time restart with row 0.
if (noMoreRowsToDisplay)
rowFirst = rowCurrent = 0;
#else
// Scrollmode 2 scrolls by row. If the rows don't fit on the screen,
// then start one row further on next time. If they do fit, then
// show them in order and start next page at row 0.
if (countNonBlankRows() <= numScreenRows) {
rowFirst = rowCurrent = 0;
} else {
// Find first non-blank row after the previous first row
rowCurrent = rowFirst;
do {
moveToNextRow();
} while (isCurrentRowBlank());
rowFirst = rowCurrent;
}
#endif
noMoreRowsToDisplay = false;
slot = 0;
lastScrollTime = currentMillis;
return NULL;
}
}
}
} while (force);
return NULL;
}
bool Display::isCurrentRowBlank() {
return (rowBuffer[rowCurrent][0] == '\0');
}
void Display::moveToNextRow() {
// Skip blank rows
if (++rowCurrent >= MAX_CHARACTER_ROWS)
rowCurrent = 0;
}
uint8_t Display::countNonBlankRows() {
uint8_t count = 0;
for (uint8_t rowNumber=0; rowNumber<MAX_CHARACTER_ROWS; rowNumber++) {
if (rowBuffer[rowNumber][0] != '\0')
count++;
}
return count;
}