Adapted from previous implementation in !476.  To quote:

> This saves about 1 mA when the display is off.

Previously, such lines would be drawn as a fuzzy two-pixel wide line
instead of a sharp one-pixel one.  This is because the coordinate grid
is aligned _between_ pixels instead of on the pixel centers.  More
information in this cairo FAQ:

    https://www.cairographics.org/FAQ/#sharp_lines



For odd linewidths, add 0.5 to all coordinates to offset the line
perfectly onto the pixel grid.  This makes them look sharp, as with the
previous gfx code.
Suggested-by: Øyvind Kolås <pippin@gimp.org>

Not sure why I didn't do this right away, but using 1.95 makes the
circles look much better.  Using 2 leads to a small artifact on the
right side so we have to stay slightly below...

Reimplement `epic_disp_blit()` without relying on the gfx library.

Make the new ctx based implementation behave just like the old one.
This means _including_ the yend row and xend column.

This fixes the G-Watch and DigiClk not looking as they should.

Replace the gfx-based implementations of the Epicardium display API
calls with ctx-based ones that try to mimick the old behavior as much as
possible.  In the long run, these functions are just meant for backwards
compatibility while new code should interface with ctx directly (once
this becomes possible).

The implementations in this changeset are closely based on pippin's
original Pycardium display API reimplementation.
Co-developed-by: Øyvind Kolås <pippin@gimp.org>

Move the display API code into the display/ subdirectory as well.

To not try and replace the entire gfx stack at once, start by "splicing
in" the new driver for the two to work alongside each other.  Primarily
the new driver takes control now and we reconfigure the orientation on
the fly whenever the old driver wants to update the screen.

Timer frequency is now held close to a value which can be achieved both
with a 48 MHz PCLK (96 MHz system clock) and a 7.5 MHz PCLK (15 MHz
system clock).

If even lower PCLKs should be supported, the frequency of the timer has
to be changed as well.

Philip Stewart authored Oct 05, 2019 and Rahix committed Oct 05, 2019

Fix two bugs in the display/gfx module:

1. The animation of the simple_menu used in the main menu had the issue
   that there is a black line visible at the top.  This is due the
   gfx_puts method ignoring lines, where the top pixel of the string is
   above the top of the screen.  As gfx_puts uses gfx_setpixel which in
   turn ignores pixels outside of the screen, remove the check in
   gfx_puts.
2. X and Y coordinates were cast to unsigned-ints before being given to
   the gfx-library which means calls like circ(0, -10, 30) would be draw
   at coordinates like [0,65526].  Fix this by changing the data-type of
   all coordinates to signed-integers.

Also remove the x and y ranges from the documentation of the individual
python functions and instead add a general documentation about the
screen and it's size/coordinate system.

Signed-off-by: Rahix <rahix@rahix.de>

Mateusz Zalega authored Aug 15, 2019 and Rahix committed Aug 15, 2019

Signed-off-by: Mateusz Zalega <mateusz@appliedsourcery.com>

Mateusz Zalega authored Aug 12, 2019 and Rahix committed Aug 12, 2019

This commit substitutes the vendor gfx library with a completely
new implementation.  It also adds a text-buffer mode.
Signed-off-by: Mateusz Zalega <mateusz@appliedsourcery.com>

Signed-off-by: Rahix <rahix@rahix.de>