Bug with libctru where background colours appear behind text when its not been exclusively programmed to

[hoffmeister-3ds]

What's the issue you encountered?
My 3DS homebrew project, which displays text on the top screen, shows corrupted output with libctru 2.5.0-2. The issues include:
Framebuffer reported as 240x400 (rotated 90 degrees counterclockwise) instead of the expected 400x240, causing vertical rectangles and rotated/mirrored text.

Incorrect colours: red background (\x1b[41m or RGB: 255, 0, 0) appears "weird" (pinkish/washed out), grey (\x1b[47m) and black (\x1b[40m) backgrounds are inconsistent.

Console rendering corruption: text like "Hello World!" appears with incorrect backgrounds (e.g., grey instead of black for "Press start to exit").

Earlier attempts showed white backgrounds with horizontal lines.

The project worked correctly with older libctru versions (pre-2.x, e.g., 1.7.0), suggesting a regression. No changes were made to devkitPro tooling beyond updating libctru via pacman -Syu, which installed 2.5.0-2.
How can the issue be reproduced?
Install devkitARM on Windows with libctru 2.5.0-2 (via pacman).

Create a 3DS homebrew project in C:/test with this main.c:
c

#include <3ds.h>
#include <stdio.h>

int main(int argc, char* argv[]) {
aptInit();
gfxInitDefault();
PrintConsole topConsole;
consoleInit(GFX_TOP, &topConsole);
consoleSelect(&topConsole);
printf("\x1b[2J\x1b[41m");
printf("\x1b[2;1H\x1b[37;1m\x1b[47mHello World!\n");
printf("\x1b[3;1H\x1b[37;1m\x1b[47m------------\n");
printf("\x1b[5;1H\x1b[37;1m\x1b[40mPress start to exit\x1b[0m");
gfxFlushBuffers();
gfxSwapBuffers();
gspWaitForVBlank();
while (aptMainLoop()) {
hidScanInput();
u32 kDown = hidKeysDown();
if (kDown & KEY_START) break;
gfxFlushBuffers();
gfxSwapBuffers();
gspWaitForVBlank();
}
gfxExit();
aptExit();
return 0;
}

Use a standard Makefile with -lctru (mine also references -lsf2d, -lcitro2d, -lcitro3d, but only main.c is compiled).

Compile: cd /c/test; make.

Copy test.3dsx to a 3DS SD card and run via a homebrew launcher.

Expected Output:
Top screen: Vibrant red background, "Hello World!" and "------------" (white on grey), "Press START to exit" (white on black).

Actual Output:
Top screen: White background with horizontal lines, all text on grey (including "Press start to exit"). With framebuffer code (e.g., GSP_BGR8_OES), a weird red background, horizontal grey/black rectangles, and rotated/mirrored text (e.g., "TEST" as "E", "IZ", "I").

Bottom screen (framebuffer debug): Debug: Start, FB: 0x30000000, W: 240, H: 400, Debug: Rendered.

Environment?
Host OS: Windows, using devkitPro’s MSYS2 shell (not cmd or PowerShell).
env.txt excerpt (redacted): DEVKITPRO=/opt/devkitpro, DEVKITARM=/opt/devkitpro/devkitARM.

Official Release: libctru 2.5.0-2 from devkitPro’s pacman repository (confirmed via pacman -Q | grep libctru).

3DS Details: [Please fill in, e.g., Old 3DS XL, firmware 11.17.0-50U].

Additional context?
Environment Details:
Project path: C:/test.

Single source file: source/main.c (confirmed via ls /c/test/source/*.c).

pacman -Syu showed no newer libctru version available as of June 17, 2025.

Attempts to Fix:
Tried GSP_RGB565_OES and GSP_BGR8_OES: Improved red but didn’t fix rotation.

Direct framebuffer writes: Produced rotated 240x400 buffer, garbled text.

ANSI codes: Incorrect colours (e.g., \x1b[41m as magenta, \x1b[40m as grey).

Workaround: Planning to downgrade to libctru 1.7.0 (git clone https://github.com/devkitPro/libctru; git checkout v1.7.0; make; make install), as older code worked with pre-2.x versions.

Suspected Issues:
gfxGetFramebuffer returns incorrect 240x400 dimensions.

Console ANSI colour rendering broken.

Colour mapping issues in gfxInit variants.

I can provide screenshots if required.

[WinterMute]

The 3DS screens are rotated - they're mobile phone screens intended for use in portrait mode. The 240x400 dimensions are correct.

The text console currently only supports GSP_RGB565_OES mode and explicitly sets this mode in consoleInit. Changing mode afterwards will result in distorted text.

The code you've supplied here won't produce a red background since that's set after the clear screen sequence is sent.

None of this changed between 1.7.0 and 2.5.0 although some codes were broken by @piepie62's code to allow escape codes split across multiple writes. The refactor in #581 fixes those and will be merged soon.

Self compiled old versions are not supported.

[hoffmeister-3ds]

Apologies, this is the code I was supposed to use:

#include <3ds.h>
#include <stdio.h>

int main(int argc, char* argv[]) {
    // Initialize services
    gfxInitDefault();
    gfxSetDoubleBuffering(GFX_TOP, false); // Single-buffering

    // Initialize console on top screen
    PrintConsole topConsole;
    consoleInit(GFX_TOP, &topConsole);
    consoleSelect(&topConsole);

    // Clear console
    consoleClear();

    // Flush buffers multiple times
    gfxFlushBuffers();
    gfxSwapBuffers();
    gspWaitForVBlank();
    gfxFlushBuffers();
    gfxSwapBuffers();
    gspWaitForVBlank();

    // Print text
    printf("\x1b[2;1H\x1b[37;1mHello World!\n");
    printf("\x1b[3;1H\x1b[37;1m------------\n");
    printf("\x1b[5;1H\x1b[37;1mPress start to exit\x1b[0m");

    // Final flush
    gfxFlushBuffers();
    gfxSwapBuffers();
    gspWaitForVBlank();

    // Main loop
    while (aptMainLoop()) {
        hidScanInput();
        u32 kDown = hidKeysDown();
        if (kDown & KEY_START) break;
    }

    // Cleanup
    gfxExit();
    return 0;
}

For some reason the colour behind the heading, the underline and the prompt produce a grey colour - it didnt do that in the previous version.

[hoffmeister-3ds]

[hoffmeister-3ds]

libctru 2.6.1-1 has just made this worse...

[WinterMute]

Apologies I messed this up. Will hopefully fix this today.

[hoffmeister-3ds]

Legend, thank you :D

[hoffmeister-3ds]

Thank you so much, this works a treat! :D