add ResizingPanel class and autolayout for Panels (#2086)

* add autolayout for Panels and new ResizingPanel

docs/Lua API.rst

@@ -3705,6 +3705,23 @@ Has attributes:
 
   Called from ``onRenderBody``.
 
+* ``autoarrange_subviews = bool`` (default: false)
+* ``autoarrange_gap = int`` (default: 0)
+
+  If ``autoarrange_subviews`` is set to ``true``, the Panel will
+  automatically handle subview layout. Subviews are laid out vertically
+  according to their current height, with ``autoarrange_gap`` empty lines
+  between subviews. This allows you to have widgets dynamically change
+  height or become visible/hidden and you don't have to worry about
+  recalculating subview positions.
+
+ResizingPanel class
+-------------------
+
+Subclass of Panel; automatically adjusts its own frame height according to
+the size, position, and visibility of its subviews. Pairs nicely with a
+parent Panel that has ``autoarrange_subviews`` enabled.
+
 Pages class
 -----------
 

docs/changelog.txt

@@ -75,6 +75,8 @@ changelog.txt uses a syntax similar to RST, with a few special sequences:
 - Lua wrappers for functions reverse-engineered from ambushing unit code: ``isHidden(unit)``, ``isFortControlled(unit)``, ``getOuterContainerRef(unit)``, ``getOuterContainerRef(item)``
 - ``dwarfmode.enterSidebarMode()``: passing ``df.ui_sidebar_mode.DesignateMine`` now always results in you entering ``DesignateMine`` mode and not ``DesignateChopTrees``, even when you looking at the surface where the default designation mode is ``DesignateChopTrees``
 - New string class function: ``string:escape_pattern()`` escapes regex special characters within a string
+- ``widgets.Panel``: if ``autoarrange_subviews`` is set, ``Panel``\s will now automatically lay out widgets vertically according to their current height.  This allows you to have widgets dynamically change height or become visible/hidden and you don't have to worry about recalculating frame layouts
+- ``widgets.ResizingPanel``: new ``Panel`` subclass that automatically recalculates it's own frame height based on the size, position, and visibility of its subviews
 - ``safe_index`` now properly handles lua sparse tables that are indexed by numbers
 
 # 0.47.05-r4

library/lua/gui/widgets.lua

@@ -75,6 +75,8 @@ Panel = defclass(Panel, Widget)
 Panel.ATTRS {
     on_render = DEFAULT_NIL,
     on_layout = DEFAULT_NIL,
+    autoarrange_subviews = false, -- whether to automatically lay out subviews
+    autoarrange_gap = 0, -- how many blank lines to insert between widgets
 }
 
 function Panel:init(args)
@@ -89,6 +91,50 @@ function Panel:postComputeFrame(body)
     if self.on_layout then self.on_layout(body) end
 end
 
+-- if self.autoarrange_subviews is true, lay out visible subviews vertically,
+-- adding gaps between widgets according to self.autoarrange_gap.
+function Panel:postUpdateLayout()
+    if not self.autoarrange_subviews then return end
+
+    local gap = self.autoarrange_gap
+    local y = 0
+    for _,subview in ipairs(self.subviews) do
+        subview.frame.t = y
+        if subview.visible then
+            y = y + subview.frame.h + gap
+        end
+    end
+    self.frame_rect.height = y
+
+    -- let widgets adjust to their new positions
+    self:updateSubviewLayout()
+end
+
+-------------------
+-- ResizingPanel --
+-------------------
+
+ResizingPanel = defclass(ResizingPanel, Panel)
+
+function ResizingPanel:init()
+    -- ensure we have a frame so a containing widget can read our dimensions
+    if not self.frame then self.frame = {} end
+end
+
+-- adjust our frame dimensions according to positions and sizes of our subviews
+function ResizingPanel:postUpdateLayout(frame_body)
+    local w, h = 0, 0
+    for _,subview in ipairs(self.subviews) do
+        if subview.visible then
+            w = math.max(w, (subview.frame.l or 0) +
+                            (subview.frame.w or frame_body.width))
+            h = math.max(h, (subview.frame.t or 0) +
+                            (subview.frame.h or frame_body.height))
+        end
+    end
+    self.frame.w, self.frame.h = w, h
+end
+
 -----------
 -- Pages --
 -----------