Description improvements (#1846)

* Increase character limit for media descriptions to 1500

It was increased in Mastodon 3.0.0 which was released in October 2019.

* Improve image description view

Since media descriptions can be longer now, we need to adjust the UI.
It is a common problem that description takes up the whole screen, it's
hard for readers and also discourages people from adding descriptions.

This commit uses bottom sheet to hide most of the description. Since we
know how much screen space it will cover, we can use darker background
which makes reading text easier.

* Adjust description handle

* Fix unable to dismiss image caption

app/src/main/java/com/keylesspalace/tusky/fragment/ViewMediaFragment.kt

@@ -17,18 +17,20 @@ package com.keylesspalace.tusky.fragment
 
 import android.os.Bundle
 import android.text.TextUtils
-import android.widget.TextView
-
 import com.keylesspalace.tusky.ViewMediaActivity
 import com.keylesspalace.tusky.entity.Attachment
-import com.keylesspalace.tusky.util.visible
 
 abstract class ViewMediaFragment : BaseFragment() {
     private var toolbarVisibiltyDisposable: Function0<Boolean>? = null
 
-    abstract fun setupMediaView(url: String, previewUrl: String?)
+    abstract fun setupMediaView(
+            url: String,
+            previewUrl: String?,
+            description: String?,
+            showingDescription: Boolean
+    )
+
     abstract fun onToolbarVisibilityChange(visible: Boolean)
-    abstract val descriptionView: TextView
 
     protected var showingDescription = false
     protected var isDescriptionVisible = false
@@ -36,6 +38,7 @@ abstract class ViewMediaFragment : BaseFragment() {
     companion object {
         @JvmStatic
         protected val ARG_START_POSTPONED_TRANSITION = "startPostponedTransition"
+
         @JvmStatic
         protected val ARG_ATTACHMENT = "attach"
         @JvmStatic
@@ -74,13 +77,10 @@ abstract class ViewMediaFragment : BaseFragment() {
 
     protected fun finalizeViewSetup(url: String, previewUrl: String?, description: String?) {
         val mediaActivity = activity as ViewMediaActivity
-        setupMediaView(url, previewUrl)
 
-        descriptionView.text = description ?: ""
         showingDescription = !TextUtils.isEmpty(description)
         isDescriptionVisible = showingDescription
-
-        descriptionView.visible(showingDescription && mediaActivity.isToolbarVisible)
+        setupMediaView(url, previewUrl, description, showingDescription && mediaActivity.isToolbarVisible)
 
         toolbarVisibiltyDisposable = (activity as ViewMediaActivity)
                 .addToolbarVisibilityListener { isVisible ->