generalize lv-font creation

In https://github.com/InfiniTimeOrg/InfiniTime/pull/1097 new font
generation capabilites were added. Generalize the font creation to
make it possible to reuse the `displayapp/fonts/CMakeLists.txt` file
for `InfiniSim` and just add the new cmake file to the project and
link against the new `infinitime_fonts` target.

In the following a list of changes.

Allow non-global installed `lv_font_conv` executable installed with

```sh
npm install lv_font_conv@1.5.2
```

In CMake we search for `lv_font_conv` executable. Add the found
executable to the python script `generate.py`, to remove the need for
`lv_font_conv` to be in the path.

Search for `python3` executable, if CMake version 3.12 is available.
Otherwise use `python` as hard coded executable.

Instead of adding the generated fonts to `SOURCE_FILES` variable, create
a static library `infinitime_fonts`. Link this library to the
executables instead.

Use `add_custom_target()` together with `add_custom_command()` to
generate the font.c files once (like the original PR does).

1 files changed, 5 insertions, 4 deletions

diff --git a/src/displayapp/fonts/generate.py b/src/displayapp/fonts/generate.py
index 401d47ab..89810614 100755
--- a/src/displayapp/fonts/generate.py
+++ b/src/displayapp/fonts/generate.py
@@ -18,8 +18,8 @@ class Source(object):
         self.symbols = d.get('symbols')
 
 
-def gen_lvconv_line(dest: str, size: int, bpp: int, sources: typing.List[Source], compress:bool=False):
-    args = ['lv_font_conv', '--size', str(size), '--output', dest, '--bpp', str(bpp), '--format', 'lvgl']
+def gen_lvconv_line(lv_font_conv: str, dest: str, size: int, bpp: int, sources: typing.List[Source], compress:bool=False):
+    args = [lv_font_conv, '--size', str(size), '--output', dest, '--bpp', str(bpp), '--format', 'lvgl']
     if not compress:
         args.append('--no-compress')
     for source in sources:
@@ -35,9 +35,10 @@ def main():
     ap = argparse.ArgumentParser(description='auto generate LVGL font files from fonts')
     ap.add_argument('config', type=str, help='config file to use')
     ap.add_argument('-f', '--font', type=str, action='append', help='Choose specific fonts to generate (default: all)', default=[])
+    ap.add_argument('--lv-font-conv', type=str, help='Path to "lv_font_conf" executable', default="lv_font_conv")
     args = ap.parse_args()
 
-    if not shutil.which('lv_font_conv'):
+    if not shutil.which(args.lv_font_conv):
         sys.exit(f'Missing lv_font_conv. (make sure it is installed and in PATH)')
     if not os.path.exists(args.config):
         sys.exit(f'Error: the config file {args.config} does not exist.')
@@ -62,7 +63,7 @@ def main():
         sources = font.pop('sources')
         patches = font.pop('patches') if 'patches' in font else  []
         font['sources'] = [Source(thing) for thing in sources]
-        line = gen_lvconv_line(f'{name}.c', **font)
+        line = gen_lvconv_line(args.lv_font_conv, f'{name}.c', **font)
         subprocess.check_call(line)
         if patches:
             for patch in patches: