Proper text previews

Fixes #17828

* Modified the preview provider to provider smaller fonts for the
  previes (so it is not so screaming)
* Modified the sidebar to show plain text and markdown files full size.

Signed-off-by: Roeland Jago Douma <roeland@famdouma.nl>
Signed-off-by: npmbuildbot[bot] <npmbuildbot[bot]@users.noreply.github.com>

apps/files/src/views/Sidebar.vue

@@ -176,6 +176,7 @@ export default {
 					starred: this.fileInfo.isFavourited,
 					subtitle: this.subtitle,
 					title: this.fileInfo.name,
+					'data-mimetype': this.fileInfo.mimetype,
 				}
 			} else if (this.error) {
 				return {
@@ -381,8 +382,17 @@ export default {
 </script>
 <style lang="scss" scoped>
 #app-sidebar {
-	&.has-preview::v-deep .app-sidebar-header__figure {
-		background-size: cover;
+	&.has-preview::v-deep {
+		.app-sidebar-header__figure {
+			background-size: cover;
+		}
+
+		&[data-mimetype="text/plain"],
+		&[data-mimetype="text/markdown"] {
+			.app-sidebar-header__figure {
+				background-size: contain;
+			}
+		}
 	}
 }
 </style>

lib/private/Preview/TXT.php

@@ -68,7 +68,7 @@ class TXT extends ProviderV2 {
 		$lines = preg_split("/\r\n|\n|\r/", $content);
 
 		// Define text size of text file preview
-		$fontSize = $maxX ? (int) ((2 / 32) * $maxX) : 5; //5px
+		$fontSize = $maxX ? (int) ((1 / 32) * $maxX) : 5; //5px
 		$lineSize = ceil($fontSize * 1.5);
 
 		$image = imagecreate($maxX, $maxY);