Does a four-scan OUTDOOR panel support DOUBLE-BUFFER feature?

[JemZhu]

Does a four-scan OUTDOOR panel support DOUBLE-BUFFER feature? I'M using 5 32x32 four-scan panels to build a display cube. I want to get a smooth display, so I turn on the double-buffer flag, but it's not working. here is my code to use the double-buffer feature:
HUB75_I2S_CFG mxconfig(
PANEL_RES_X * 2, // Virtual width
PANEL_RES_Y / 2, // Virtual height
NUM_ROWS * NUM_COLS,
_pins
);
mxconfig.double_buff = true;
// Initialize display
dma_display = new MatrixPanel_I2S_DMA(mxconfig);
if (!dma_display->begin()) {
Serial.println("ERROR: Could not start display!");
while (true);
}

FourScanPanel = new VirtualMatrixPanel((*dma_display), NUM_ROWS, NUM_COLS, PANEL_RES_X, PANEL_RES_Y);
FourScanPanel->setPhysicalPanelScanRate(FOUR_SCAN_32PX_HIGH);
dma_display->setBrightness8(255);

void testpanel(){
for (int y = 0; y < 32; y++) {
for (int x = 0; x < 64; x++) {
uint8_t r = 255;
uint8_t g = 0;
uint8_t b = 0;

    FourScanPanel->drawPixelRGB888(x, y, r, g, b);
  }
}

dma_display->flipDMABuffer();

while(1);
}

The testpanel function give a total black output ? please help.

[mrcodetastic]

The DMA buffering is independent from the pixel mapping layer which is the "VirtualMatrixPanel" class.

You need to draw to the back buffer before you flip to it.

Draw -> Flip (show) -> Draw -> Flip (show)