2512: Allow more than 5 tabs (#4051)

Fixes #2512 


![grafik](https://github.com/tuskyapp/Tusky/assets/1618905/f8199d10-e26a-4f14-93c3-95cb890ea663)

Can add an arbitrary number of tabs.
Graphical behavior is unchanged for small numbers: the whole space if
filled with the tabs - they are enlarged if needed.

If there are more the mode switches to "scrollable".
This does not, however, look very differently (see screenshot with the
current tab scrolled out).

---------

Co-authored-by: Konrad Pozniak <connyduck@users.noreply.github.com>

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

@@ -0,0 +1,41 @@
+package com.keylesspalace.tusky.view
+
+import android.content.Context
+import android.util.AttributeSet
+import android.view.ViewGroup
+import com.google.android.material.tabs.TabLayout
+
+/**
+ * Workaround for "auto" mode not behaving as expected.
+ *
+ * Switches the tab display mode depending on available size: start out with "scrollable" but
+ * if there is enough room switch to "fixed" (and re-measure).
+ *
+ * Idea taken from https://stackoverflow.com/a/44894143
+ */
+class AdaptiveTabLayout @JvmOverloads constructor(
+    context: Context,
+    attrs: AttributeSet? = null,
+    defStyleAttr: Int = 0
+) : TabLayout(context, attrs, defStyleAttr) {
+
+    override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
+        tabMode = MODE_SCROLLABLE // make sure to only measure the "minimum width"
+        super.onMeasure(widthMeasureSpec, heightMeasureSpec)
+
+        if (tabCount < 2) {
+            return
+        }
+
+        val tabLayout = getChildAt(0) as ViewGroup
+        var widthOfAllTabs = 0
+        for (i in 0 until tabLayout.childCount) {
+            widthOfAllTabs += tabLayout.getChildAt(i).measuredWidth
+        }
+        if (widthOfAllTabs <= measuredWidth) {
+            // fill all space if there is enough room
+            tabMode = MODE_FIXED
+            super.onMeasure(widthMeasureSpec, heightMeasureSpec)
+        }
+    }
+}