Issues rewriting text with color & background = TFT_BLACK

aportela commented 4 months ago

Environment ( 実行環境 )

MCU or Board name: [ESP-WROOM-32|]
Panel Driver IC: [ST7796]
Bus type: [SPI]
LovyanGFX version: [v1.1.16]
FrameWork version: [ArduinoESP32 v2.0.13]
Build Environment: [ArduinoIDE]
Operating System: [Windows]

Problem Description ( 問題の内容 )

When rewriting a string above another at the same coordinates and size with black color, the original string is not completely deleted. If I use a color other than black, the original string is deleted correctly and the new one is written over it.

Personally I use it in many cases to avoid having to use an intermediate buffer (sprite) or draw a filled box on top of the old text before drawing the new text.

Expected Behavior ( 期待される動作 )

I know that this is not the AdafruitGFX library but since it shares many things and since if I use another color other than black it works correctly, here is the idea of the procedure I use:

Overwriting Text with the Built-In Font

Actual Behavior ( 実際の動作 )

Garbage is displayed, it does not overwrite correctly

Steps to reproduce ( 再現のための前提条件 )

Use TFT_BLACK, TFT_BLACK on last setTextColor for FAIL (In theory, the specified number should be "drawn in black", meaning nothing would be seen since it would simulate a deletion of the text)
Use TFT_RED, TFT_BLACK on last setTextColor for WORK (The previous text is completely erased and the new text is displayed in red correctly)

Code to reproduce this issue ( 再現させるためのコード )

void setup()
{
    // ... LGFX init (custom pins) (my pointer LGFX is screen)
    screen->init();
    screen->fillScreen(TFT_BLACK);
    screen->setCursor(100, 100);
    screen->setTextSize(2);
    screen->setTextColor(TFT_WHITE, TFT_BLACK);
    screen->print("0123456789");
    screen->setCursor(100, 100);
    screen->setTextSize(2);
    screen->setTextColor(TFT_RED, TFT_BLACK); // THIS WORKS, CHANGE FIRST TFT_RED to TFT_BLACK FOR BUG
    screen->print("9876543210");
}

This is the picture reflecting the BUG:

photo_2024-07-20_22-23-03