feat: added quick dirty workaround to customize export font

Added a quick dirty workaround that uses environment variable
`PRESENTERM_EXPORT_FONT` to set the a custom font when exporting to pdf

CHANGELOG.md

@@ -6,12 +6,12 @@
 
 ## New features
 
-* Support for [slide transitions](https://mfontanini.github.io/presenterm/features/slide-transitons.html) is now available ([#530](https://github.com/mfontanini/presenterm/issues/530)):
+* Support for [slide transitions](https://mfontanini.github.io/presenterm/features/slide-transitions.html) is now available ([#530](https://github.com/mfontanini/presenterm/issues/530)):
   * Add fade slide transition ([#534](https://github.com/mfontanini/presenterm/issues/534)).
   * Add slide horizontally slide transition animation ([#528](https://github.com/mfontanini/presenterm/issues/528)).
   * Add `collapse_horizontal` slide transition ([#560](https://github.com/mfontanini/presenterm/issues/560)).
-* Add `--output` option to specify the path where the output file is written to during an export ([#526](https://github.com/mfontanini/presenterm/issues/526)).
-* Allow specifying [start/end lines](https://mfontanini.github.io/presenterm/features/code/highlighting.html#including-external-code-snippets) in file snippet type ([#565](https://github.com/mfontanini/presenterm/issues/565)) - thanks @marianozunino.
+* Add `--output` option to specify the path where the output file is written to during an export ([#526](https://github.com/mfontanini/presenterm/issues/526)) - thanks @marianozunino.
+* Allow specifying [start/end lines](https://mfontanini.github.io/presenterm/features/code/highlighting.html#including-external-code-snippets) in file snippet type ([#565](https://github.com/mfontanini/presenterm/issues/565)).
 * Allow letting [pauses become new slides](https://mfontanini.github.io/presenterm/configuration/settings.html#pause-behavior) when exporting ([#557](https://github.com/mfontanini/presenterm/issues/557)).
 * Allow [using images on right in footer](https://mfontanini.github.io/presenterm/features/themes/definition.html#footer-images) ([#554](https://github.com/mfontanini/presenterm/issues/554)).
 * Add [`max_rows` configuration](https://mfontanini.github.io/presenterm/configuration/settings.html#maximum-presentation-height) to cap vertical size ([#531](https://github.com/mfontanini/presenterm/issues/531)).

src/export/pdf.rs

@@ -18,7 +18,7 @@ use crate::{
 };
 use image::{ImageEncoder, codecs::png::PngEncoder};
 use std::{
-    fs, io,
+    fs, io,env,
     path::{Path, PathBuf},
 };
 
@@ -165,6 +165,12 @@ impl PdfRender {
         let width = (self.dimensions.columns as f64 * FONT_SIZE as f64 * FONT_SIZE_WIDTH).ceil();
         let height = self.dimensions.rows * LINE_HEIGHT;
         let background_color = self.background_color.unwrap_or_else(|| "black".into());
+
+        let font_family = match env::var("PRESENTERM_EXPORT_FONT") {
+            Ok(val) => format!(r"font-family: {val} !important;"),
+            Err(_) => format!(r""),
+        };
+
         let css = format!(
             r"
         pre {{
@@ -184,6 +190,10 @@ impl PdfRender {
             width: {width}px;
         }}
 
+        body * {{
+            {font_family}
+        }}
+
         .content-line {{
             line-height: {LINE_HEIGHT}px; 
             height: {LINE_HEIGHT}px;