Add prelude and core themes

Author: v-rob

builtin/ui/init.lua

@@ -27,3 +27,4 @@ dofile(UI_PATH .. "style.lua")
 dofile(UI_PATH .. "elem.lua")
 dofile(UI_PATH .. "window.lua")
 dofile(UI_PATH .. "elem_defs.lua")
+dofile(UI_PATH .. "theme.lua")

builtin/ui/style.lua

@@ -218,13 +218,3 @@ function ui._encode_props(props)
 
 	return ui._encode("s", ui._encode_flags(fl))
 end
-
-local default_theme = ui.Style{}
-
-function ui.get_default_theme()
-	return default_theme
-end
-
-function ui.set_default_theme(theme)
-	default_theme = theme
-end

builtin/ui/theme.lua

@@ -0,0 +1,89 @@
+--[[
+Minetest
+Copyright (C) 2023 v-rob, Vincent Robinson <[email protected]>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License along
+with this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+--]]
+
+local prelude_theme = ui.Style{
+	ui.Style{
+		sel = "root",
+
+		-- The root window should be centered on the screen, but have no size
+		-- by default, since the size should be user-set.
+		rel_pos = {1/2, 1/2},
+		rel_anchor = {1/2, 1/2},
+		rel_size = {0, 0},
+
+		-- Normally, we don't show the backdrop unless we have user focus.
+		ui.Style{
+			sel = "@backdrop",
+			visible = false,
+		},
+		ui.Style{
+			sel = "@backdrop$focused",
+			visible = true,
+		}
+	},
+	ui.Style{
+		sel = "image",
+
+		-- We generally want images to take up as much space as possible.
+		fg_scale = 0,
+	},
+	ui.Style{
+		sel = "button, toggle, check, switch",
+
+		-- By default, buttons, toggle buttons, checkboxes, radio buttons, and
+		-- switches have their image placed on the left side by default.
+		fg_halign = "left",
+	},
+}
+
+function ui.get_prelude_theme()
+	return prelude_theme
+end
+
+local core_theme = ui.Style{
+	-- Like any good theme should, we include the prelude theme first.
+	prelude_theme,
+
+	-- TODO
+	ui.Style{
+		sel = "root",
+
+		bg_fill = "black#8C",
+
+		ui.Style{
+			sel = "@backdrop",
+
+			bg_fill = "black#50",
+		},
+	},
+}
+
+function ui.get_core_theme()
+	return core_theme
+end
+
+local default_theme = core_theme
+
+function ui.get_default_theme()
+	return default_theme
+end
+
+function ui.set_default_theme(theme)
+	default_theme = theme
+end