add unit tests for widgets.Scrollbar

library/lua/gui/widgets.lua

@@ -397,7 +397,8 @@ function Scrollbar:update(top_elem, elems_per_page, num_elems)
         num_elems))
 
     local max_pos = scrollbar_body_height - height
-    local pos = math.ceil(((top_elem-1) * max_pos) /
+    local pos = (num_elems == elems_per_page) and 0 or
+            math.ceil(((top_elem-1) * max_pos) /
                       (num_elems - elems_per_page))
 
     self.top_elem = top_elem

test/library/gui/widgets.Scrollbar.lua

@@ -0,0 +1,93 @@
+local gui = require('gui')
+local widgets = require('gui.widgets')
+
+function test.update()
+    local s = widgets.Scrollbar{}
+    s.frame_body = {height=100} -- give us some space to work with
+
+    -- initial defaults
+    expect.eq(1, s.top_elem)
+    expect.eq(1, s.elems_per_page)
+    expect.eq(1, s.num_elems)
+    expect.eq(0, s.bar_offset)
+    expect.eq(1, s.bar_height)
+
+    -- top_elem, elems_per_page, num_elems
+    s:update(1, 10, 0)
+    expect.eq(1, s.top_elem)
+    expect.eq(10, s.elems_per_page)
+    expect.eq(0, s.num_elems)
+    expect.eq(0, s.bar_offset)
+    expect.eq(1, s.bar_height)
+
+    -- first 10 of 50 shown
+    s:update(1, 10, 50)
+    expect.eq(1, s.top_elem)
+    expect.eq(10, s.elems_per_page)
+    expect.eq(50, s.num_elems)
+    expect.eq(0, s.bar_offset)
+    expect.eq(19, s.bar_height)
+
+    -- bottom 10 of 50 shown
+    s:update(41, 10, 50)
+    expect.eq(41, s.top_elem)
+    expect.eq(10, s.elems_per_page)
+    expect.eq(50, s.num_elems)
+    expect.eq(79, s.bar_offset)
+    expect.eq(19, s.bar_height)
+
+    -- ~middle 10 of 50 shown
+    s:update(23, 10, 50)
+    expect.eq(23, s.top_elem)
+    expect.eq(10, s.elems_per_page)
+    expect.eq(50, s.num_elems)
+    expect.eq(44, s.bar_offset)
+    expect.eq(19, s.bar_height)
+end
+
+function test.onInput()
+    local spec = nil
+    local mock_on_scroll = function(scroll_spec) spec = scroll_spec end
+    local s = widgets.Scrollbar{on_scroll=mock_on_scroll}
+    s.frame_body = {height=100} -- give us some space to work with
+    local y = nil
+    s.getMousePos = function() return 0, y end
+
+    -- put scrollbar somewhere in the middle so we can click above and below it
+    s:update(23, 10, 50)
+
+    expect.false_(s:onInput{}, 'no mouse down')
+    expect.false_(s:onInput{_MOUSE_L_DOWN=true}, 'no y coord')
+
+    spec, y = nil, 0
+    expect.true_(s:onInput{_MOUSE_L_DOWN=true})
+    expect.eq('up_small', spec, 'on up arrow')
+
+    spec, y = nil, 1
+    expect.true_(s:onInput{_MOUSE_L_DOWN=true})
+    expect.eq('up_large', spec, 'on body above bar')
+
+    spec, y = nil, 44
+    expect.true_(s:onInput{_MOUSE_L_DOWN=true})
+    expect.eq('up_large', spec, 'on body just above bar')
+
+    spec, y = nil, 45
+    expect.true_(s:onInput{_MOUSE_L_DOWN=true})
+    expect.nil_(spec, 'on top of bar')
+
+    spec, y = nil, 63
+    expect.true_(s:onInput{_MOUSE_L_DOWN=true})
+    expect.nil_(spec, 'on bottom of bar')
+
+    spec, y = nil, 64
+    expect.true_(s:onInput{_MOUSE_L_DOWN=true})
+    expect.eq('down_large', spec, 'on body just below bar')
+
+    spec, y = nil, 98
+    expect.true_(s:onInput{_MOUSE_L_DOWN=true})
+    expect.eq('down_large', spec, 'on body below bar')
+
+    spec, y = nil, 99
+    expect.true_(s:onInput{_MOUSE_L_DOWN=true})
+    expect.eq('down_small', spec, 'on down arrow')
+end