extmod/modframebuf: Make monochrome bitmap formats start with MONO_.

MONO_xxx is much easier to read if you're not familiar with the code.
MVLSB is deprecated but kept for backwards compatibility, for the time
being.

This patch also updates the associated docs and tests.

docs/library/framebuf.rst

@@ -116,9 +116,32 @@ Other methods
 Constants
 ---------
 
-.. data:: framebuf.MVLSB
+.. data:: framebuf.MONO_VLSB
 
     Monochrome (1-bit) color format
+    This defines a mapping where the bits in a byte are vertically mapped with
+    bit 0 being nearest the top of the screen. Consequently each byte occupies
+    8 vertical pixels. Subsequent bytes appear at successive horizontal
+    locations until the rightmost edge is reached. Further bytes are rendered
+    at locations starting at the leftmost edge, 8 pixels lower.
+
+.. data:: framebuf.MONO_HLSB
+
+    Monochrome (1-bit) color format
+    This defines a mapping where the bits in a byte are horizontally mapped.
+    Each byte occupies 8 horizontal pixels with bit 0 being the leftmost.
+    Subsequent bytes appear at successive horizontal locations until the
+    rightmost edge is reached. Further bytes are rendered on the next row, one
+    pixel lower.
+
+.. data:: framebuf.MONO_HMSB
+
+    Monochrome (1-bit) color format
+    This defines a mapping where the bits in a byte are horizontally mapped.
+    Each byte occupies 8 horizontal pixels with bit 7 being the leftmost.
+    Subsequent bytes appear at successive horizontal locations until the
+    rightmost edge is reached. Further bytes are rendered on the next row, one
+    pixel lower.
 
 .. data:: framebuf.RGB565
 

extmod/modframebuf.c

@@ -579,10 +579,11 @@ STATIC const mp_rom_map_elem_t framebuf_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR_FrameBuffer), MP_ROM_PTR(&mp_type_framebuf) },
     { MP_ROM_QSTR(MP_QSTR_FrameBuffer1), MP_ROM_PTR(&legacy_framebuffer1_obj) },
     { MP_ROM_QSTR(MP_QSTR_MVLSB), MP_OBJ_NEW_SMALL_INT(FRAMEBUF_MVLSB) },
+    { MP_ROM_QSTR(MP_QSTR_MONO_VLSB), MP_OBJ_NEW_SMALL_INT(FRAMEBUF_MVLSB) },
     { MP_ROM_QSTR(MP_QSTR_RGB565), MP_OBJ_NEW_SMALL_INT(FRAMEBUF_RGB565) },
     { MP_ROM_QSTR(MP_QSTR_GS4_HMSB), MP_OBJ_NEW_SMALL_INT(FRAMEBUF_GS4_HMSB) },
-    { MP_ROM_QSTR(MP_QSTR_MHLSB), MP_OBJ_NEW_SMALL_INT(FRAMEBUF_MHLSB) },
-    { MP_ROM_QSTR(MP_QSTR_MHMSB), MP_OBJ_NEW_SMALL_INT(FRAMEBUF_MHMSB) },
+    { MP_ROM_QSTR(MP_QSTR_MONO_HLSB), MP_OBJ_NEW_SMALL_INT(FRAMEBUF_MHLSB) },
+    { MP_ROM_QSTR(MP_QSTR_MONO_HMSB), MP_OBJ_NEW_SMALL_INT(FRAMEBUF_MHMSB) },
 };
 
 STATIC MP_DEFINE_CONST_DICT(framebuf_module_globals, framebuf_module_globals_table);

tests/extmod/framebuf1.py

@@ -9,9 +9,9 @@ w = 5
 h = 16
 size = w * h // 8
 buf = bytearray(size)
-maps = {framebuf.MVLSB : 'MVLSB',
-        framebuf.MHLSB : 'MHLSB',
-        framebuf.MHMSB : 'MHMSB'}
+maps = {framebuf.MONO_VLSB : 'MONO_VLSB',
+        framebuf.MONO_HLSB : 'MONO_HLSB',
+        framebuf.MONO_HMSB : 'MONO_HMSB'}
 
 for mapping in maps.keys():
     for x in range(size):
@@ -107,3 +107,4 @@ except ValueError:
 # test legacy constructor
 fbuf = framebuf.FrameBuffer1(buf, w, h)
 fbuf = framebuf.FrameBuffer1(buf, w, h, w)
+print(framebuf.MVLSB == framebuf.MONO_VLSB)

tests/extmod/framebuf1.py.exp

@@ -1,4 +1,4 @@
-MVLSB
+MONO_VLSB
 0
 bytearray(b'\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff')
 bytearray(b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00')
@@ -20,7 +20,7 @@ bytearray(b'\x00\x7f\x7f\x04\x04\x00\x00\x00\x00\x00')
 bytearray(b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00')
 bytearray(b'\xaaU\xaaU\xaa\x00\x00\x00\x00\x00')
 
-MHLSB
+MONO_HLSB
 0
 bytearray(b'\xf8\xf8\xf8\xf8\xf8\xf8\xf8\xf8\xf8\xf8')
 bytearray(b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00')
@@ -42,7 +42,7 @@ bytearray(b'``x````\x00\x00\x00')
 bytearray(b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00')
 bytearray(b'P\xa8P\xa8P\xa8P\xa8\x00\x00')
 
-MHMSB
+MONO_HMSB
 0
 bytearray(b'\x1f\x1f\x1f\x1f\x1f\x1f\x1f\x1f\x1f\x1f')
 bytearray(b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00')
@@ -65,3 +65,4 @@ bytearray(b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00')
 bytearray(b'\n\x15\n\x15\n\x15\n\x15\x00\x00')
 
 ValueError
+True