H/V Lines not appearing Giga GFX library demo

Official Hardware Mega GIGA Display Shield
1

Not sure if this is a Giga display problem, or something in the underlying Adafruit GFX library...
I ran the demo in the Arduino_GigaDisplay_GFX repo and noticed that one section
(the tests for drawFastH/VLine) was not being displayed.

The sketch is a cut down version of the demo in the Arduino_GigaDisplay_GFX gitbug repo.

EDIT: References to memory corruption removed. My mistake here.

#include "Arduino_GigaDisplay_GFX.h"

GigaDisplay_GFX tft;

#define GC9A01A_CYAN    (uint16_t)0x07FF
#define GC9A01A_RED     (uint16_t)0xf800
#define GC9A01A_BLUE    (uint16_t)0x001F
#define GC9A01A_GREEN   (uint16_t)0x07E0
#define GC9A01A_MAGENTA (uint16_t)0xF81F
#define GC9A01A_WHITE   (uint16_t)0xffff
#define GC9A01A_BLACK   (uint16_t)0x0000
#define GC9A01A_YELLOW  (uint16_t)0xFFE0


unsigned long testFillScreen() {
  unsigned long start = micros();
  tft.fillScreen(GC9A01A_BLACK);
  yield();
  return micros() - start;
}


unsigned long testFastLines(uint16_t color1, uint16_t color2) {
  unsigned long start;
  int16_t           x, y;
  int16_t           w = tft.width();
  int16_t           h = tft.height();

  Serial.println(w);
  Serial.println(h);
  //tft.fillScreen(GC9A01A_BLACK);
  //yield();
  Serial.println(w);
  Serial.println(h);

  start = micros();
  // no need for drawfast routines as they are called automatically in adafruitGFX
 // for (y = 0; y < h; y += 6) tft.drawFastHLine(0, y, w, color1);
 // for (x = 0; x < w; x += 6) tft.drawFastVLine(x, 0, h, color2);
  for (y = 0; y < h; y += 6) tft.drawLine(0, y, w, y, color1);
  for (x = 0; x < w; x += 6) tft.drawLine(x, 0, x, h, color2);
  //yield();
  return micros() - start;
}

void setup() {
  Serial.begin(9600);
  Serial.println("GC9A01A Test!");

  tft.begin();
  Serial.println(tft.width());
  Serial.println(tft.height());   // verify correct width/height

  Serial.println(F("Benchmark                Time (microseconds)"));
  delay(10);
  //Serial.print(F("Screen fill              "));
  //Serial.println(testFillScreen());
  //delay(500);

  Serial.print(F("Horiz/Vert Lines         "));
  Serial.println(testFastLines(GC9A01A_RED, GC9A01A_BLUE));
  delay(500);


  Serial.println(F("Done!"));
}

void loop(void) {
}
2

may be relevant here too.

3

Some of this may be related to some issues I ran into when I played with this library.

There are places that don't trigger a redraw of the screen.
In the case I ran into was the tft.fillScreen(...)

I submitted a PR to resolve this, back on February 5th.
fillScreen: trigger a redraw of the screen by KurtE · Pull Request #3 · arduino-libraries/Arduino_GigaDisplay_GFX (github.com)

So far this PR has not been touched since then, other than @ptillisch marked it
as a bug, that day...

4

Thanks Kurt, will apply that and see what happens. Might need to be sprinkled around in other places too. Of more concern is that local variables seem to be corrupted by another thread.

EDIT: The local variables are fine. My bad - I was confused by the order of the printfs.
Applying PR #3 allowed the fillScreen to work, but no lines came out unless I put a display.print("Done") right at the end. So other kinds of graphics calls need the endWrite() treatment too, it seems. Probably explains why the original demo appeared to work but when it was cut down to finish on the line test it didn't.

5

Problem solved. The changes to PR #3 need to be also applied to drawFastRawHLine and drawFastRawVline. I'll put a comment to that effect in the PR if I can. Any calls that don't drop down to the Adafruit GFX will be similar, but I don't think there are any apart from drawPixel, which tends to be called as part of other things.

6

In order to make all relevant information available to any who are interested in this subject, I'll share a link to the pull request submitted by @aegidius:

Thanks for your contribution @aegidius!