gui/mass-remove.toolbar: position is constrained to minimum-size interface

This limits the possible positions, but prevents a couple of problems
when the overlay's "anchor edges" change (i.e., after "touching" a
different interface edge while repositioning the overlay):

- unexpected "jumps" of the overlay's effective position
- "stale" overlay size representation in `gui/overlay`

Both of these were caused by swapping the "padding" from one side of the
overlay's effective position to the other when swapping anchor edges.

Always apply both paddings to keep things consistent.

Author: ChrisJohnsen

gui/mass-remove.lua

@@ -407,10 +407,17 @@ end
 -- l/r/t/b frame positioning fields). However, to preserve player-positioning,
 -- we take a more circuitous route.
 
--- The button and tooltip are anchored to one side of the overlay's frame (which
--- one depends on which edge the overlay itself is anchored to). Then, to
--- respond to different interface sizes, we adjust the width and height of the
--- overlay's frame to arrange for the button to land in its expected place.
+-- In a minimum-size interface area, the player is allowed to place the overlay
+-- (a combination of the button and the tooltip) anywhere inside the interface
+-- area. When the interface area is resized (usually through window resizes, but
+-- also through interface percentage changes), placement is maintained relative
+-- to the "ideal" position of the button (i.e. positions are relative to the
+-- "ideal" position). When repositioning the overlay in a larger-than-minimum
+-- interface area the overlays size is artificially inflated so that the overlay
+-- can not be positioned (with respect to the "ideal" button position) farther
+-- away than is possible in a minimum-size interface area. This limits the
+-- positioning, but keeps the (relative) position consistent across all possible
+-- resizes.
 
 local tb = reqscript('internal/df-bottom-toolbars')
 
@@ -509,29 +516,17 @@ function MassRemoveToolbarOverlay:init()
 end
 
 function MassRemoveToolbarOverlay:preUpdateLayout(parent_rect)
-    local extra_width
     local offsets = mass_remove_button_offsets(parent_rect)
-    if self.frame.l then
-        extra_width = offsets.l - MR_MIN_OFFSETS.l
-        self.subviews.tt_and_icon.frame.l = nil
-        self.subviews.tt_and_icon.frame.r = 0
-    else
-        extra_width = offsets.r - MR_MIN_OFFSETS.r
-        self.subviews.tt_and_icon.frame.l = 0
-        self.subviews.tt_and_icon.frame.r = nil
-    end
-    local extra_height
-    if self.frame.b then
-        extra_height = offsets.b - MR_MIN_OFFSETS.b
-        self.subviews.tt_and_icon.frame.t = 0
-        self.subviews.tt_and_icon.frame.b = nil
-    else
-        extra_height = offsets.t - MR_MIN_OFFSETS.t
-        self.subviews.tt_and_icon.frame.t = nil
-        self.subviews.tt_and_icon.frame.b = 0
-    end
-    self.frame.w = MR_WIDTH + extra_width
-    self.frame.h = MR_HEIGHT + extra_height
+    local r = offsets.r - MR_MIN_OFFSETS.r
+    local l = offsets.l - MR_MIN_OFFSETS.l
+    local t = offsets.t - MR_MIN_OFFSETS.t
+    local b = offsets.b - MR_MIN_OFFSETS.b
+    self.frame.w = MR_WIDTH + l + r
+    self.frame.h = MR_HEIGHT + t + b
+    self.subviews.tt_and_icon.frame.l = l
+    self.subviews.tt_and_icon.frame.r = r
+    self.subviews.tt_and_icon.frame.t = t
+    self.subviews.tt_and_icon.frame.b = b
 end
 
 function MassRemoveToolbarOverlay:onInput(keys)