layout: make position: fixed, sticky act like static

It's better to not implement them at all than to implement them badly.

(In particular, making fixed act like absolute breaks horribly on
websites that actually use it. Fixing it is not really possible without
changinge the way we currently draw things to the screen.)

1 files changed, 8 insertions, 7 deletions

diff --git a/src/layout/engine.nim b/src/layout/engine.nim
index 06e95cdc..049da947 100644
--- a/src/layout/engine.nim
+++ b/src/layout/engine.nim
@@ -1150,7 +1150,7 @@ const DisplayBlockLike = {DISPLAY_BLOCK, DISPLAY_LIST_ITEM,
 
 # Return true if no more margin collapsing can occur for the current strut.
 func canFlushMargins(builder: BlockBoxBuilder, sizes: ResolvedSizes): bool =
-  if builder.computed{"position"} in {POSITION_ABSOLUTE, POSITION_FIXED}:
+  if builder.computed{"position"} == POSITION_ABSOLUTE:
     return false
   return sizes.padding.top != 0 or sizes.padding.bottom != 0 or
     builder.inlinelayout or builder.computed{"display"} notin DisplayBlockLike
@@ -1272,7 +1272,7 @@ proc positionFloats(bctx: var BlockContext) =
 
 func establishesBFC(computed: CSSComputedValues): bool =
   return computed{"float"} != FLOAT_NONE or
-    computed{"position"} in {POSITION_ABSOLUTE, POSITION_FIXED} or
+    computed{"position"} in POSITION_ABSOLUTE or
     computed{"display"} in {DISPLAY_INLINE_BLOCK, DISPLAY_FLOW_ROOT} +
       InternalTableBox
     #TODO overflow, contain, flex, grid, multicol, column-span
@@ -2176,8 +2176,8 @@ proc layoutBlockChildren(state: var BlockState, bctx: var BlockContext,
     var dy: LayoutUnit = 0 # delta
     var child: BlockBox
     let isfloat = builder.computed{"float"} != FLOAT_NONE
-    let isinflow = builder.computed{"position"} notin {POSITION_ABSOLUTE,
-      POSITION_FIXED} and not isfloat
+    let isinflow = builder.computed{"position"} != POSITION_ABSOLUTE
+      and not isfloat
     if builder.computed.establishesBFC():
       var marginBottomOut: LayoutUnit
       child = bctx.lctx.layoutRootBlock(builder, state.space, state.offset,
@@ -2206,8 +2206,7 @@ proc layoutBlockChildren(state: var BlockState, bctx: var BlockContext,
     let childWidth = child.margin.left + child.size.w + child.margin.right
     state.maxChildWidth = max(state.maxChildWidth, childWidth)
     state.xminwidth = max(state.xminwidth, child.xminwidth)
-    if child.computed{"position"} notin {POSITION_ABSOLUTE, POSITION_FIXED} and
-        not isfloat:
+    if child.computed{"position"} != POSITION_ABSOLUTE and not isfloat:
       # Not absolute, and not a float.
       state.offset.y += dy
     elif isfloat:
@@ -2299,7 +2298,9 @@ proc repositionChildren(state: BlockState, box: BlockBox, lctx: LayoutState) =
 proc layoutBlock(bctx: var BlockContext, box: BlockBox,
     builder: BlockBoxBuilder, sizes: ResolvedSizes) =
   let lctx = bctx.lctx
-  let positioned = box.computed{"position"} != POSITION_STATIC
+  let positioned = box.computed{"position"} != {
+    POSITION_STATIC, POSITION_FIXED, POSITION_STICKY
+  }
   if positioned:
     lctx.positioned.add(sizes.space)
   var state = BlockState(