2dpainting

[Shao]

Hi,
I can build and run the example "2dpainting" on my Host PC (Ubuntu20.04).

I copy the whole example directory to my embedded device (google-coral dev board).
I can build the example project but run uncorrect.
It show my the whole black window.

I add some related library in 2dpaint.pro

LIBS += -lGLESv2 -lm -lEGL -lwayland-client -lwayland-egl

It show something, but some color in opengl is wrong.
So I change some code in helper.cpp paint brush in exmaple.
ex:

    QLinearGradient gradient(QPointF(50, -20), QPointF(80, 20));
    gradient.setColorAt(0.0, Qt::white);
    gradient.setColorAt(1.0, QColor(0xa6, 0xce, 0x39));

    background = QBrush(QColor(64, 32, 64));
    circleBrush = QBrush(gradient);
    circlePen = QPen(Qt::black);
    circlePen.setWidth(1);
    textPen = QPen(Qt::white);
    textFont.setPixelSize(50);

change to

/*
    QLinearGradient gradient(QPointF(50, -20), QPointF(80, 20));
    gradient.setColorAt(0.0, QColor(255,255,255));
    gradient.setColorAt(1.0, QColor(0xa6, 0xce, 0x39));
*/

    background = QBrush(QColor(64, 32, 64));
    circleBrush = QBrush(QColor(0xa6,0xce,0x39));
    circlePen = QPen(Qt::black);
    circlePen.setWidth(1);
    textPen = QPen(Qt::red);  //white is also work
    textFont.setPixelSize(50);

Here is two problem

1. How to fix QLinearGradient ?
2. How to cancel the white background on text(Qt) ?