fix(i1): fix compiler and runtime issues with I1 rendering (#6714)

Co-authored-by: Liam <30486941+liamHowatt@users.noreply.github.com>

docs/porting/display.rst

@@ -136,7 +136,6 @@ or anything else to optimize while the waiting for flush.
 If ``flush_wait_cb`` is not set, LVGL assume that `lv_display_flush_ready`
 is used.
 
-
 Rotation
 --------
 
@@ -173,7 +172,7 @@ The default color format of the display is set according to :c:macro:`LV_COLOR_D
 - :c:macro:`LV_COLOR_DEPTH` ``24``: RGB888 (3 bytes/pixel)
 - :c:macro:`LV_COLOR_DEPTH` ``16``: RGB565 (2 bytes/pixel)
 - :c:macro:`LV_COLOR_DEPTH` ``8``: L8 (1 bytes/pixel)
-- :c:macro:`LV_COLOR_DEPTH` ``1``: I1 (1 bit/pixel) Only support for horizontal mapped buffers.
+- :c:macro:`LV_COLOR_DEPTH` ``1``: I1 (1 bit/pixel) Only support for horizontal mapped buffers. See :refr:`monochrome` for more details:
 
 The ``color_format`` can be changed with
 :cpp:expr:`lv_display_set_color_depth(display, LV_COLOR_FORMAT_...)`.
@@ -205,6 +204,40 @@ to
 
 ``GGG BBBBB | RRRRR GGG``.
 
+.. _monochrome:
+
+Monochrome Displays
+-------------------
+
+LVGL supports rendering directly in a 1-bit format for monochrome displays.
+To enable it, set ``LV_COLOR_DEPTH 1`` or use :cpp:expr:`lv_display_set_color_format(display, LV_COLOR_FORMAT_I1)`.
+
+The :cpp:expr:`LV_COLOR_FORMAT_I1` format assumes that bytes are mapped to rows (i.e., the bits of a byte are written next to each other).
+The order of bits is MSB first, which means:
+
+.. code::
+
+             MSB           LSB
+   bits       7 6 5 4 3 2 1 0
+   pixels     0 1 2 3 4 5 6 7
+             Left         Right
+
+Ensure that the LCD controller is configured accordingly.
+
+Internally, LVGL rounds the redrawn areas to byte boundaries. Therefore, updated areas will:
+
+- Start on an ``Nx8`` coordinate.
+- End on an ``Nx8 - 1`` coordinate.
+
+When setting up the buffers for rendering (:cpp:func:`lv_display_set_buffers`), make the buffer 8 bytes larger.
+This is necessary because LVGL reserves 2 x 4 bytes in the buffer, as these are assumed to be used as a palette.
+
+To skip the palette, include the following line in your ``flush_cb`` function: ``px_map += 8``.
+
+As usual, monochrome displays support partial, full, and direct rendering modes as well.
+In full and direct modes, the buffer size should be large enough for the whole screen, meaning ``(horizontal_resolution x vertical_resolution / 8) + 8`` bytes.
+As LVGL can not handle fractional width make sure to round the horizontal resolution to 8-
+(For example 90 to 96)
 
 User data
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