compute height in Javascript to avoid hovered image jumping

src/General/UI.coffee

@@ -302,7 +302,7 @@ UI = do ->
       $.off d, 'mouseup',   @up
     $.set "#{@id}.position", @style.cssText
 
-  hoverstart = ({root, el, latestEvent, endEvents, asapTest, cb, noRemove}) ->
+  hoverstart = ({root, el, latestEvent, endEvents, asapTest, height, cb, noRemove}) ->
     o = {
       root
       el
@@ -313,6 +313,7 @@ UI = do ->
       latestEvent
       clientHeight: doc.clientHeight
       clientWidth:  doc.clientWidth
+      height
       noRemove
     }
     o.hover    = hover.bind    o
@@ -335,7 +336,7 @@ UI = do ->
 
   hover = (e) ->
     @latestEvent = e
-    height = @el.offsetHeight
+    height = @height or @el.offsetHeight
     {clientX, clientY} = e
 
     top = if @isImage

src/General/css/style.css

@@ -837,13 +837,6 @@ span.hide-announcement {
 .fileThumb > .warning {
   clear: both;
 }
-#ihover {
-  -moz-box-sizing: border-box;
-  box-sizing: border-box;
-  max-height: 100%;
-  max-width: 75%;
-  padding-bottom: 16px;
-}
 /* Fappe Tyme */
 :root.fappeTyme .thread > .noFile,
 :root.fappeTyme .threadContainer > .noFile {

src/Images/ImageHover.coffee

@@ -31,18 +31,28 @@ ImageHover =
       el.loop     = true
       el.controls = false
       el.play() if Conf['Autoplay']
+    [width, height] = file.dimensions.split('x').map (x) -> +x
+    {left, right} = file.thumb.getBoundingClientRect()
+    padding = 16
+    maxWidth = Math.max left, doc.clientWidth - right
+    maxHeight = doc.clientHeight - padding
+    scale = Math.min 1, maxWidth / width, maxHeight / height
+    el.style.maxWidth = "#{scale * width}px"
+    el.style.maxHeight = "#{scale * height}px"
     UI.hover
       root: @
       el: el
       latestEvent: e
       endEvents: 'mouseout click'
-      asapTest: -> (if isVideo then el.readyState >= el.HAVE_CURRENT_DATA else el.naturalHeight)
+      asapTest: -> true
+      height: scale * height + padding
       noRemove: true
       cb: ->
         if isVideo
           el.pause()
         TrashQueue.add el, post
         el.removeAttribute 'id'
+        el.removeAttribute 'style'
         $.queueTask -> delete file.isHovered
   error: ->
     post = Get.postFromNode @