Add option to not crop image previews (#2832)

* Don't crop image previews with aspects between 2:1 & 1:2

Fixes #1995

* Custom media preview layout for handling various aspect ratios

app/src/main/java/com/keylesspalace/tusky/util/AttachmentHelper.kt

@@ -1,4 +1,5 @@
 @file:JvmName("AttachmentHelper")
+
 package com.keylesspalace.tusky.util
 
 import android.content.Context
@@ -24,3 +25,12 @@ private fun formatDuration(durationInSeconds: Double): String {
     val hours = durationInSeconds.toInt() / 3600
     return "%d:%02d:%02d".format(hours, minutes, seconds)
 }
+
+fun List<Attachment>.aspectRatios(): List<Double> {
+    return map { attachment ->
+        // clamp ratio between 2:1 & 1:2, defaulting to 16:9
+        val size = (attachment.meta?.small ?: attachment.meta?.original) ?: return@map 1.7778
+        val aspect = if (size.aspect > 0) size.aspect else size.width.toDouble() / size.height
+        aspect.coerceIn(0.5, 2.0)
+    }
+}