Configurable themes

Configurable in settings.php
Looks for bootswatch themes named bootstrap.[theme].min.css
Defaults to bootstrap.min.css ('materia')
Bundled additional themes 'darkly' and 'slate'

app.php

@@ -29,7 +29,7 @@ if (!empty($_GET['page'])) {
 
 header("Link: <static/img/logo.svg>; rel=preload; as=image", false);
 header("Link: <static/fonts/Roboto.css>; rel=preload; as=style", false);
-header("Link: <static/css/bootstrap.min.css>; rel=preload; as=style", false);
+header("Link: <static/css/".$themefile.">; rel=preload; as=style", false);
 header("Link: <static/css/material-color/material-color.min.css>; rel=preload; as=style", false);
 header("Link: <static/css/app.css>; rel=preload; as=style", false);
 if (FONTAWESOME_USEJS) {
@@ -52,7 +52,7 @@ header("Link: <static/js/bootstrap.bundle.min.js>; rel=preload; as=script", fals
 
         <link rel="icon" href="static/img/logo.svg" type="image/svg+xml">
 
-        <link href="static/css/bootstrap.min.css" rel="stylesheet">
+        <link href="static/css/<?php echo $themefile; ?>" rel="stylesheet">
         <link href="static/css/material-color/material-color.min.css" rel="stylesheet">
         <link href="static/css/app.css" rel="stylesheet">
         <?php

index.php

@@ -36,7 +36,7 @@ function showHTML(string $title, string $button, string $url) {
 
     <link rel="icon" href="static/img/logo.svg">
 
-    <link href="static/css/bootstrap.min.css" rel="stylesheet">
+    <link href="static/css/<?php echo $themefile; ?>" rel="stylesheet">
     <style nonce="<?php echo $SECURE_NONCE; ?>">
         .display-5 {
             font-size: 2.5rem;

required.php

@@ -94,6 +94,13 @@ function sendError($error) {
 
 date_default_timezone_set($SETTINGS['timezone']);
 
+// Set theme
+if (file_exists('static/css/bootstrap.'.$SETTINGS['theme'].'.min.css')) {
+    $themefile = 'bootstrap.'.$SETTINGS['theme'].'.min.css';
+} else {
+    $themefile = 'bootstrap.min.css';
+}
+
 // Database settings
 // Also inits database and stuff
 use Medoo\Medoo;

settings.template.php

@@ -47,6 +47,9 @@ $SETTINGS = [
     "timezone" => "America/Denver",
     // Language to use for localization. See langs folder to add a language.
     "language" => "en",
+    // Theme to use. Choose between "materia" (light)(default), "slate" (dark) or "darkly" (dark).
+    // You can also add your own bootswatch theme (https://bootswatch.com/).
+    "theme" => "materia",
     // Shown in the footer of all the pages.
     "footer_text" => "",
     // Also shown in the footer, but with "Copyright <current_year>" in front.