[Docs] Quantum Painter Draw Image Example Code Is Wrong And Causes uint16_t Overflow

[EricBanker12]

Issue Description

Quantum Painter Drawing API > Image Functions > Draw Image has the following example code:

// Draw an image on the bottom-right of the 240x320 display on initialisation
static painter_image_handle_t my_image;
void keyboard_post_init_kb(void) {
    my_image = qp_load_image_mem(gfx_my_image);
    if (my_image != NULL) {
        qp_drawimage(display, (239 - my_image->width), (319 - my_image->height), my_image);
    }
}

This example code will actually display an image 1 pixel up-left of the bottom-right corner of the 240x320 display. Additionally, it will cause uint16_t overflow for images the same size as the display. To correct this, it should be changed to the following:

// Draw an image on the bottom-right of the 240x320 display on initialisation
static painter_image_handle_t my_image;
void keyboard_post_init_kb(void) {
    my_image = qp_load_image_mem(gfx_my_image);
    if (my_image != NULL) {
        qp_drawimage(display, (240 - my_image->width), (320 - my_image->height), my_image);
    }
}

---

I have confirmed this uint16_t overflow behavior using a 96x24 test image with a SteelSeries Prime+ which has a 96x24 display.

qp_drawimage(display, 96 - my_image->width, 24 - my_image->height, my_image);

qp_drawimage(display, 95 - my_image->width, 23 - my_image->height, my_image);

In addition to this issue on Quantum Painter Drawing API > Image Functions > Draw Image, similar issues exist for example code under:

• Quantum Painter Drawing API > Image Functions > Animate Image
• Quantum Painter Drawing API > Font Functions > Draw Text

Link to docs page: https://docs.qmk.fm/quantum_painter#quantum-painter-api

[EricBanker12]

Changed uint16_t overflow example image host from Discord to Imgur due to Discord's external link expiration.