feat(ui): let a widget opt out of the pressed style

A custom node that paints its own key highlight does not want the whole
node marked dirty on every press.

lua/lib/ui.lua

@@ -28,6 +28,7 @@ local ui = {}
 ---@field on_exit? UiHandler
 ---@field on_click? UiHandler
 ---@field paint? fun(id: NodeId, x: integer, y: integer, w: integer, h: integer)
+---@field press_style? boolean False for a widget that paints its own press feedback.
 
 ---@class UiConfirmSpec
 ---@field title string
@@ -49,6 +50,9 @@ local THEMES = {
 }
 
 local enterHandlers, exitHandlers, clickHandlers, painters = {}, {}, {}, {}
+-- A widget that paints its own press feedback opts out, so pressing one key does not
+-- repaint the whole node the way a pressed style would.
+local pressStyles = {}
 local laidOut = false
 local themeName
 local activeScreen
@@ -119,6 +123,7 @@ loadTheme(savedTheme and savedTheme:match("^%s*(.-)%s*$") or "light")
 
 local function clearState()
   enterHandlers, exitHandlers, clickHandlers, painters = {}, {}, {}, {}
+  pressStyles = {}
 end
 
 node.setPainter(function(id, x, y, w, h)
@@ -164,6 +169,7 @@ local function build(spec, kind)
   exitHandlers[id] = spec.on_exit
   clickHandlers[id] = spec.on_click
   painters[id] = spec.paint
+  pressStyles[id] = spec.press_style ~= false
   return id
 end
 
@@ -340,13 +346,13 @@ local function inside(id, x, y)
 end
 
 local function enter(id, x, y)
-  node.setPressed(id, true)
+  if pressStyles[id] then node.setPressed(id, true) end
   local handler = enterHandlers[id]
   if handler then handler(id, x, y) end
 end
 
 local function exit(id, x, y)
-  node.setPressed(id, false)
+  if pressStyles[id] then node.setPressed(id, false) end
   local handler = exitHandlers[id]
   if handler then handler(id, x, y) end
 end

lua/test/ui.lua

@@ -194,4 +194,24 @@ assert(columns == 3 and side == 93, "width is the binding constraint in portrait
 -- Five cards are two rows, so a reserve that eats the height budget shrinks the card.
 assert(select(1, ui.cardSide(5, 12, 8, 300)) == 74, "height binds once the reserve is large")
 
+-- A widget painting its own feedback is never given a pressed style, while an ordinary one
+-- still is. Which node was hit is geometry, so the test names the target directly.
+ui.reset()
+local pressedCalls = {}
+node.setPressed = function(_, on) pressedCalls[#pressedCalls + 1] = on end
+local own = ui.custom{h = 20, press_style = false, on_click = function() end}
+local styled = ui.button{h = 20, label = "ok", on_click = function() end}
+local board = ui.screen(ui.box{own, styled})
+local target
+node.hit = function() return target end
+
+target = own
+board:down(0, 0)
+board:up(0, 0)
+assert(#pressedCalls == 0, "a self-painting widget is not styled on press")
+
+target = styled
+board:down(0, 0)
+assert(pressedCalls[1] == true, "an ordinary widget still gets its pressed style")
+
 print("ok")