3408 home help message (#3415)

* 3408: First draft of help message on empty home timeline

* 3408: Move image spanning to utils; tweak gui a bit (looks like status)

* 3408: Use proper R again; appease linter

* 3408: Add doc; remove narrow comment

* 3408: null is default

* 3408: Add German text

* 3408: Stack refresh animation on top of help message (reorder)

app/src/main/java/com/keylesspalace/tusky/components/timeline/TimelineFragment.kt

@@ -236,6 +236,9 @@ class TimelineFragment :
                         if (loadState.append is LoadState.NotLoading && loadState.source.refresh is LoadState.NotLoading) {
                             binding.statusView.show()
                             binding.statusView.setup(R.drawable.elephant_friend_empty, R.string.message_empty)
+                            if (kind == TimelineViewModel.Kind.HOME) {
+                                binding.statusView.showHelp(R.string.help_empty_home)
+                            }
                         }
                     }
                     is LoadState.Error -> {

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

@@ -1,10 +1,19 @@
 package com.keylesspalace.tusky.util
 
+import android.content.Context
+import android.graphics.drawable.Drawable
+import android.os.Build
 import android.text.Spannable
+import android.text.SpannableStringBuilder
 import android.text.Spanned
 import android.text.style.CharacterStyle
+import android.text.style.DynamicDrawableSpan
 import android.text.style.ForegroundColorSpan
+import android.text.style.ImageSpan
 import android.text.style.URLSpan
+import androidx.appcompat.content.res.AppCompatResources
+import com.mikepenz.iconics.IconicsDrawable
+import com.mikepenz.iconics.typeface.library.googlematerial.GoogleMaterial
 import java.util.regex.Pattern
 import kotlin.math.max
 
@@ -61,6 +70,66 @@ private class PatternFinder(
     val pattern: Pattern = Pattern.compile(regex, Pattern.CASE_INSENSITIVE)
 }
 
+/**
+ * Takes text containing mentions and hashtags and urls and makes them the given colour.
+ */
+fun highlightSpans(text: Spannable, colour: Int) {
+    // Strip all existing colour spans.
+    for (spanClass in spanClasses) {
+        clearSpans(text, spanClass)
+    }
+
+    // Colour the mentions and hashtags.
+    val string = text.toString()
+    val length = text.length
+    var start = 0
+    var end = 0
+    while (end in 0 until length && start >= 0) {
+        // Search for url first because it can contain the other characters
+        val found = findPattern(string, end)
+        start = found.start
+        end = found.end
+        if (start in 0 until end) {
+            text.setSpan(getSpan(found.matchType, string, colour, start, end), start, end, Spanned.SPAN_INCLUSIVE_EXCLUSIVE)
+            start += finders[found.matchType]!!.searchPrefixWidth
+        }
+    }
+}
+
+/**
+ * Replaces text of the form [drawabale name] or [iconics name] with their spanned counterparts (ImageSpan).
+ */
+fun addDrawables(text: CharSequence, color: Int, size: Int, context: Context): Spannable {
+    val alignment = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) DynamicDrawableSpan.ALIGN_CENTER else DynamicDrawableSpan.ALIGN_BASELINE
+
+    val builder = SpannableStringBuilder(text)
+
+    val pattern = Pattern.compile("\\[(drawable|iconics) ([0-9a-z_]+)\\]")
+    val matcher = pattern.matcher(builder)
+    while (matcher.find()) {
+        val resourceType = matcher.group(1)
+        val resourceName = matcher.group(2)
+            ?: continue
+
+        val drawable: Drawable? = when (resourceType) {
+            "iconics" -> IconicsDrawable(context, GoogleMaterial.getIcon(resourceName))
+            else -> {
+                val drawableResourceId = context.resources.getIdentifier(resourceName, "drawable", context.packageName)
+                if (drawableResourceId != 0) AppCompatResources.getDrawable(context, drawableResourceId) else null
+            }
+        }
+
+        if (drawable != null) {
+            drawable.setBounds(0, 0, size, size)
+            drawable.setTint(color)
+
+            builder.setSpan(ImageSpan(drawable, alignment), matcher.start(), matcher.end(), Spannable.SPAN_EXCLUSIVE_EXCLUSIVE)
+        }
+    }
+
+    return builder
+}
+
 private fun <T> clearSpans(text: Spannable, spanClass: Class<T>) {
     for (span in text.getSpans(0, text.length, spanClass)) {
         text.removeSpan(span)
@@ -136,30 +205,6 @@ private fun getSpan(matchType: FoundMatchType, string: String, colour: Int, star
     }
 }
 
-/** Takes text containing mentions and hashtags and urls and makes them the given colour. */
-fun highlightSpans(text: Spannable, colour: Int) {
-    // Strip all existing colour spans.
-    for (spanClass in spanClasses) {
-        clearSpans(text, spanClass)
-    }
-
-    // Colour the mentions and hashtags.
-    val string = text.toString()
-    val length = text.length
-    var start = 0
-    var end = 0
-    while (end in 0 until length && start >= 0) {
-        // Search for url first because it can contain the other characters
-        val found = findPattern(string, end)
-        start = found.start
-        end = found.end
-        if (start in 0 until end) {
-            text.setSpan(getSpan(found.matchType, string, colour, start, end), start, end, Spanned.SPAN_INCLUSIVE_EXCLUSIVE)
-            start += finders[found.matchType]!!.searchPrefixWidth
-        }
-    }
-}
-
 private fun isWordCharacters(codePoint: Int): Boolean {
     return (codePoint in 0x30..0x39) || // [0-9]
         (codePoint in 0x41..0x5a) || // [A-Z]

app/src/main/java/com/keylesspalace/tusky/view/BackgroundMessageView.kt

@@ -6,15 +6,16 @@ import android.view.Gravity
 import android.view.LayoutInflater
 import android.view.View
 import android.widget.LinearLayout
+import android.widget.TextView
 import androidx.annotation.DrawableRes
 import androidx.annotation.StringRes
 import com.keylesspalace.tusky.R
 import com.keylesspalace.tusky.databinding.ViewBackgroundMessageBinding
+import com.keylesspalace.tusky.util.addDrawables
 import com.keylesspalace.tusky.util.visible
 
 /**
- * This view is used for screens with downloadable content which may fail.
- * Can show an image, text and button below them.
+ * This view is used for screens with content which may be empty or might have failed to download.
  */
 class BackgroundMessageView @JvmOverloads constructor(
     context: Context,
@@ -47,4 +48,15 @@ class BackgroundMessageView @JvmOverloads constructor(
         binding.button.setOnClickListener(clickListener)
         binding.button.visible(clickListener != null)
     }
+
+    fun showHelp(@StringRes helpRes: Int) {
+        val size: Int = binding.helpText.textSize.toInt() + 2
+        val color = binding.helpText.currentTextColor
+        val text = context.getText(helpRes)
+        val textWithDrawables = addDrawables(text, color, size, context)
+
+        binding.helpText.setText(textWithDrawables, TextView.BufferType.SPANNABLE)
+
+        binding.helpText.visible(true)
+    }
 }