fit_widget(): Sanitize the result of :fit()

After this change, fit_widget() enforces that a widget cannot ask for more space
than was offered to it. This also fixes a rounding issue in the flex layout
where its fit function would return too small numbers.

Thanks to this, lots of "XXX" comments in spec/ disappear.

Signed-off-by: Uli Schlachter <psychon@znc.in>

lib/wibox/layout/base.lua

@@ -26,7 +26,12 @@ function base.fit_widget(context, widget, width, height)
     local width = math.max(0, width)
     local height = math.max(0, height)
 
-    return widget._fit_geometry_cache:get(context, width, height)
+    local w, h = widget._fit_geometry_cache:get(context, width, height)
+
+    -- Also sanitize the output.
+    w = math.max(0, math.min(w, width))
+    h = math.max(0, math.min(h, height))
+    return w, h
 end
 
 --- Draw a widget via a cairo context

lib/wibox/layout/flex.lua

@@ -80,8 +80,8 @@ function flex:fit(context, orig_width, orig_height)
     local used_in_other = 0
 
     -- Figure out the maximum size we can give out to sub-widgets
-    local sub_height = self.dir == "x" and orig_height or floor(orig_height / #self.widgets)
+    local sub_height = self.dir == "x" and orig_height or orig_height / #self.widgets
-    local sub_width  = self.dir == "y" and orig_width  or floor(orig_width / #self.widgets)
+    local sub_width  = self.dir == "y" and orig_width  or orig_width / #self.widgets
 
     for k, v in pairs(self.widgets) do
         local w, h = base.fit_widget(context, v, sub_width, sub_height)

spec/wibox/layout/align_spec.lua

@@ -56,8 +56,7 @@ describe("wibox.layout.flex", function()
 
             describe("without enough height", function()
                 it("fit", function()
-                    -- XXX: Is this really what should happen?
+                    assert.widget_fit(layout, { 5, 100 }, { 5, 35 })
-                    assert.widget_fit(layout, { 5, 100 }, { 15, 35 })
                 end)
 
                 it("draw", function()
@@ -72,16 +71,14 @@ describe("wibox.layout.flex", function()
 
             describe("without enough width", function()
                 it("fit", function()
-                    -- XXX: Is this really what should happen?
+                    assert.widget_fit(layout, { 100, 20 }, { 15, 20 })
-                    assert.widget_fit(layout, { 100, 20 }, { 15, 35 })
                 end)
 
                 it("draw", function()
                     layout:draw("wibox", "cr", 100, 20)
-                    --- XXX: Shouldn't this also draw part of the second widget?
                     utils.check_widgets_drawn({
-                        { first,  0,  0, 100, 10 },
+                        { first,  0,  0, 100,  2 },
-                        { third,  0, 10, 100, 10 },
+                        { third,  0, 18, 100,  2 },
                         { second, 0,  2, 100, 15 },
                     })
                 end)
@@ -135,8 +132,7 @@ describe("wibox.layout.flex", function()
 
             describe("without enough height", function()
                 it("fit", function()
-                    -- XXX: Is this really what should happen?
+                    assert.widget_fit(layout, { 5, 100 }, { 5, 35 })
-                    assert.widget_fit(layout, { 5, 100 }, { 15, 35 })
                 end)
 
                 it("draw", function()
@@ -151,8 +147,7 @@ describe("wibox.layout.flex", function()
 
             describe("without enough width", function()
                 it("fit", function()
-                    -- XXX: Is this really what should happen?
+                    assert.widget_fit(layout, { 100, 20 }, { 15, 20 })
-                    assert.widget_fit(layout, { 100, 20 }, { 15, 35 })
                 end)
 
                 it("draw", function()
@@ -213,8 +208,7 @@ describe("wibox.layout.flex", function()
 
             describe("without enough height", function()
                 it("fit", function()
-                    -- XXX: Is this really what should happen?
+                    assert.widget_fit(layout, { 5, 100 }, { 5, 35 })
-                    assert.widget_fit(layout, { 5, 100 }, { 15, 35 })
                 end)
 
                 it("draw", function()
@@ -229,8 +223,7 @@ describe("wibox.layout.flex", function()
 
             describe("without enough width", function()
                 it("fit", function()
-                    -- XXX: Is this really what should happen?
+                    assert.widget_fit(layout, { 100, 20 }, { 15, 20 })
-                    assert.widget_fit(layout, { 100, 20 }, { 15, 35 })
                 end)
 
                 it("draw", function()

spec/wibox/layout/fixed_spec.lua

@@ -54,8 +54,7 @@ describe("wibox.layout.fixed", function()
 
         describe("without enough height", function()
             it("fit", function()
-                -- XXX: Is this really what should happen?
+                assert.widget_fit(layout, { 5, 100 }, { 5, 35 })
-                assert.widget_fit(layout, { 5, 100 }, { 15, 35 })
             end)
 
             it("draw", function()
@@ -76,9 +75,10 @@ describe("wibox.layout.fixed", function()
 
             it("draw", function()
                 layout:draw("wibox", "cr", 100, 20)
-                --- XXX: Shouldn't this also draw part of the second widget?
                 utils.check_widgets_drawn({
                     { first,  0,  0, 100, 10 },
+                    { second, 0, 10, 100, 10 },
+                    { third,  0, 20, 100,  0 },
                 })
             end)
         end)

spec/wibox/layout/flex_spec.lua

@@ -54,8 +54,7 @@ describe("wibox.layout.flex", function()
 
         describe("without enough height", function()
             it("fit", function()
-                -- XXX: Is this really what should happen?
+                assert.widget_fit(layout, { 5, 100 }, { 5, 35 })
-                assert.widget_fit(layout, { 5, 100 }, { 15, 35 })
             end)
 
             it("draw", function()
@@ -70,8 +69,7 @@ describe("wibox.layout.flex", function()
 
         describe("without enough width", function()
             it("fit", function()
-                -- XXX: Is this really what should happen?
+                assert.widget_fit(layout, { 100, 20 }, { 15, 20 })
-                assert.widget_fit(layout, { 100, 20 }, { 15, 35 })
             end)
 
             it("draw", function()

spec/wibox/test_utils.lua

@@ -35,7 +35,7 @@ local function widget_fit(state, arguments)
     local widget = arguments[1]
     local given = arguments[2]
     local expected = arguments[3]
-    local w, h = widget:fit({ "fake context" }, given[1], given[2])
+    local w, h = lbase.fit_widget({ "fake context" }, widget, given[1], given[2])
 
     local fits = expected[1] == w and expected[2] == h
     if state.mod == fits then