change the way grid spacing is handled, make it more dynamic

app/src/main/kotlin/com/simplemobiletools/gallery/pro/activities/MediaActivity.kt

@@ -405,6 +405,7 @@ class MediaActivity : SimpleActivity(), MediaOperationsListener {
             }
             setupLayoutManager()
             measureRecyclerViewContent(mMedia)
+            handleGridSpacing()
         } else if (mLastSearchedText.isEmpty()) {
             (currAdapter as MediaAdapter).updateMedia(mMedia)
             measureRecyclerViewContent(mMedia)
@@ -723,6 +724,19 @@ class MediaActivity : SimpleActivity(), MediaOperationsListener {
         media_vertical_fastscroller.setScrollToY(media_grid.computeVerticalScrollOffset())
     }
 
+    private fun handleGridSpacing() {
+        if (media_grid.itemDecorationCount > 0) {
+            media_grid.removeItemDecorationAt(0)
+        }
+
+        val viewType = config.getFolderViewType(if (mShowAll) SHOW_ALL else mPath)
+        if (viewType == VIEW_TYPE_GRID) {
+            val spanCount = config.mediaColumnCnt
+            val spacing = 2
+            media_grid.addItemDecoration(GridSpacingItemDecoration(spanCount, spacing, config.scrollHorizontally))
+        }
+    }
+
     private fun initZoomListener() {
         val viewType = config.getFolderViewType(if (mShowAll) SHOW_ALL else mPath)
         if (viewType == VIEW_TYPE_GRID) {
@@ -773,6 +787,7 @@ class MediaActivity : SimpleActivity(), MediaOperationsListener {
     }
 
     private fun columnCountChanged() {
+        handleGridSpacing()
         invalidateOptionsMenu()
         getMediaAdapter()?.apply {
             notifyItemRangeChanged(0, media.size)

app/src/main/kotlin/com/simplemobiletools/gallery/pro/helpers/GridSpacingItemDecoration.kt

@@ -0,0 +1,27 @@
+package com.simplemobiletools.gallery.pro.helpers
+
+import android.graphics.Rect
+import android.view.View
+import androidx.recyclerview.widget.RecyclerView
+
+class GridSpacingItemDecoration(val spanCount: Int, val spacing: Int, val isScrollingHorizontally: Boolean) : RecyclerView.ItemDecoration() {
+
+    override fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State) {
+        val position = parent.getChildAdapterPosition(view)
+        val column = position % spanCount
+
+        if (isScrollingHorizontally) {
+            outRect.top = column * spacing / spanCount
+            outRect.bottom = spacing - (column + 1) * spacing / spanCount
+            if (position >= spanCount) {
+                outRect.left = spacing
+            }
+        } else {
+            outRect.left = column * spacing / spanCount
+            outRect.right = spacing - (column + 1) * spacing / spanCount
+            if (position >= spanCount) {
+                outRect.top = spacing
+            }
+        }
+    }
+}

app/src/main/res/layout/photo_video_item_grid.xml

@@ -5,8 +5,7 @@
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
     android:clickable="true"
-    android:focusable="true"
-    android:padding="1px">
+    android:focusable="true">
 
     <com.simplemobiletools.gallery.pro.views.MySquareImageView
         android:id="@+id/medium_thumbnail"