Correct scroll length for left and up directions

[per1234]

Previously, the calculation for the distance of leftward and upward scrolling resulted in the text bitmap not being scrolled completely off the display.

For leftward scrolling, this would be noticeable in the case where the bitmap of the last character in the string had populated pixels on the rightmost column. For upward scrolling, this would be noticeable in the case where the bitmap of any character in the string had populated pixels on the bottom row.

Demos

The incompletely scrolled pixels will not be distinguishable from the artifacts left by the unrelated bug #50, but can be seen if the fix from #51 is applied.

SCROLL_LEFT

Prior to the change proposed here, the following sketch would result in the two pixels from the rightmost column of the Font_4x6 # character bitmap would remaining on the display after scrolling:

#include <ArduinoGraphics.h>
#include <Arduino_LED_Matrix.h>

ArduinoLEDMatrix matrix;

void setup() {
  matrix.begin();
  matrix.textFont(Font_4x6);
  matrix.textScrollSpeed(200);
}

void loop() {
  matrix.beginText(matrix.width(), 1, 0xFFFFFF);
  matrix.print("#");  // The bitmap for the Font_4x6 # character has two populated pixels on the rightmost column
  matrix.endText(SCROLL_LEFT);
}

SCROLL_UP

Prior to the change proposed here, the following sketch would result in the pixel from the bottom row of the Font_4x6 ( character bitmap remaining on the display after scrolling:

#include <ArduinoGraphics.h>
#include <Arduino_LED_Matrix.h>

ArduinoLEDMatrix matrix;

void setup() {
  matrix.begin();
  matrix.textFont(Font_4x6);
  matrix.textScrollSpeed(300);
}

void loop() {
  matrix.beginText(1, matrix.height(), 0xFFFFFF);
  matrix.print("(");  // The bitmap for the Font_4x6 ( character has a populated pixel on the bottom row
  matrix.endText(SCROLL_UP);
}

[github-actions]

Memory usage change @ e0415f1

Board	flash	%	RAM for global variables	%
arduino:samd:arduino_zero_edbg	🔺 +4 - +4	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:samd:mkrzero	🔺 +4 - +4	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:samd:nano_33_iot	🔺 +4 - +4	0.0 - 0.0	0 - 0	0.0 - 0.0

Click for full report table

Board	examples/ASCIIDraw flash	%	examples/ASCIIDraw RAM for global variables	%
arduino:samd:arduino_zero_edbg	4	0.0	0	0.0
arduino:samd:mkrzero	4	0.0	0	0.0
arduino:samd:nano_33_iot	4	0.0	0	0.0

Click for full report CSV

Board,examples/ASCIIDraw<br>flash,%,examples/ASCIIDraw<br>RAM for global variables,%
arduino:samd:arduino_zero_edbg,4,0.0,0,0.0
arduino:samd:mkrzero,4,0.0,0,0.0
arduino:samd:nano_33_iot,4,0.0,0,0.0