Optionally specify margin size #396 (#411)

Whoever wants to shrink the margins, they can now do so via the new
optional command line arguments

--geometry:left
--geometry:right
--geometry:top
--geometry:bottom

which are default options in pandoc (see pandoc's documentation
[here](https://pandoc.org/demo/example33/6.2-variables.html)).

Their default value is ''. These options are not passed to pandoc when
their value is ''.

The argument parser added can be extended easily with other pandoc's
argument options. If the new options' default value is '' then they will
not be passed to pandoc.

build_ebook.py

@@ -11,6 +11,9 @@ from dataclasses import dataclass
 from subprocess import CalledProcessError
 from re import Match
 import shutil
+import argparse
+import sys
+from make_parser import make_parser
 
 logging.basicConfig(
     format="%(asctime)s %(levelname)-8s %(message)s",
@@ -148,7 +151,7 @@ def compile_full_markdown(
     return markdown_file
 
 
-def build_pdf(markdown_file: Path, pdf_file: Path) -> Path:
+def build_pdf(markdown_file: Path, pdf_file: Path, args: argparse.Namespace) -> Path:
     """Build combined Markdown file into a PDF."""
 
     try:
@@ -157,12 +160,21 @@ def build_pdf(markdown_file: Path, pdf_file: Path) -> Path:
         raise RuntimeError(f"failed to build {pdf_file}: xelatex not installed")
 
     try:
+        keys_values = [(arg, getattr(args, arg)) for arg in vars(args)]
+        opts = [f"{key}={val}" for key, val in keys_values if val != ""]
+        pandoc_args = [x for i in opts for x in ("-V", i)]
+
         subprocess.check_output(
             [
                 "pandoc",
                 markdown_file.as_posix(),
                 "-V",
-                "documentclass=report",
+                "documentclass=report"
+            ]
+            +
+            pandoc_args
+            +
+            [
                 "-t",
                 "latex",
                 "-s",
@@ -202,8 +214,10 @@ def build_epub(markdown_file: Path, epub_file: Path) -> Path:
 
     return epub_file
 
-
 def main() -> None:
+    parser = make_parser()
+    args = parser.parse_args(sys.argv[1:])
+    
     """Build ebooks."""
     with TemporaryDirectory() as raw_out_dir:
         out_dir = Path(raw_out_dir)
@@ -223,11 +237,11 @@ def main() -> None:
             )
 
             logging.info(f"{lang}: building pdf...")
-            pdf_file = build_pdf(markdown_file, out_dir / f"{lang}.pdf")
+            pdf_file = build_pdf(markdown_file, out_dir / f"{lang}.pdf", args)
 
             logging.info(f"{lang}: building epub...")
             epub_file = build_epub(markdown_file, out_dir / f"{lang}.epub")
-
+            
             shutil.copy(pdf_file, f"ebook/vulkan_tutorial_{lang}.pdf")
             shutil.copy(epub_file, f"ebook/vulkan_tutorial_{lang}.epub")
 

make_parser.py

@@ -0,0 +1,37 @@
+import argparse
+
+def make_parser() -> argparse.ArgumentParser:
+    parser = argparse.ArgumentParser(
+        description="Build the pdf and epub files of the Vulkan Tutorial."
+    )
+
+    parser.add_argument(
+        "--geometry:left",
+        type=str,
+        required=False,
+        default="",
+        help="Specify left margin space as a string. Example: 2cm.",
+    )
+    parser.add_argument(
+        "--geometry:right",
+        type=str,
+        required=False,
+        default="",
+        help="Specify right margin space as a string. Example: 2cm.",
+    )
+    parser.add_argument(
+        "--geometry:top",
+        type=str,
+        required=False,
+        default="",
+        help="Specify top margin space as a string. Example: 2cm.",
+    )
+    parser.add_argument(
+        "--geometry:bottom",
+        type=str,
+        required=False,
+        default="",
+        help="Specify bottom margin space as a string. Example: 2cm.",
+    )
+
+    return parser