Add load-save script and adjust gui/load-screen to work with it

Closes DFHack/dfhack#755

Author: lethosor

gui/load-screen.lua

@@ -469,7 +469,6 @@ function state_change_handler(evt)
     if evt ~= SC_VIEWSCREEN_CHANGED then return end
     table.remove(focus_stack, 1)
     table.insert(focus_stack, dfhack.gui.getCurFocus())
-    cur_focus = dfhack.gui.getCurFocus()
     if enabled and focus_stack[1] == 'title' and focus_stack[2] == 'loadgame' then
         mkscreen()
     end
@@ -482,8 +481,12 @@ function init()
 end
 
 function mkscreen()
-    scr = load_screen()
-    scr:show()
+    local parent = dfhack.gui.getCurViewscreen()
+    -- Create this screen only above a viewscreen_loadgamest that isn't loading a game
+    if df.viewscreen_loadgamest:is_instance(parent) and parent.loading == 0 then
+        scr = load_screen()
+        scr:show()
+    end
 end
 
 if initialized == nil then

load-save.lua

@@ -0,0 +1,80 @@
+-- load a save non-interactively - intended to be run on startup
+--[====[
+
+load-save
+=========
+
+When run on the title screen or "load game" screen, loads the save with the
+given folder name without requiring interaction.
+
+Example: ``load-save region``
+
+This can also be run when starting DFHack from the command line::
+
+    ./dfhack +load-game region1
+
+(This is currently untested on Windows)
+
+]====]
+
+local gui = require 'gui'
+
+local folder_name = ({...})[1] or qerror("No folder name given")
+
+local loadgame_screen = dfhack.gui.getViewscreenByType(df.viewscreen_loadgamest, 0)
+if not loadgame_screen then
+    local title_screen = dfhack.gui.getViewscreenByType(df.viewscreen_titlest, 0)
+    if not title_screen then
+        qerror("Can't find title or load game screen")
+    end
+    local found = false
+    for idx, item in pairs(title_screen.menu_line_id) do
+        if item == df.viewscreen_titlest.T_menu_line_id.Continue then
+            found = true
+            title_screen.sel_menu_line = idx
+            break
+        end
+    end
+    if not found then
+        qerror("Can't find 'Continue Playing' option")
+    end
+    gui.simulateInput(title_screen, 'SELECT')
+end
+
+loadgame_screen = dfhack.gui.getViewscreenByType(df.viewscreen_loadgamest, 0) or
+    qerror("Can't find load game screen")
+
+local found = false
+for idx, save in pairs(loadgame_screen.saves) do
+    if save.folder_name == folder_name then
+        found = true
+        loadgame_screen.sel_idx = idx
+        break
+    end
+end
+if not found then
+    qerror("Can't find save: " .. folder_name)
+end
+
+--[[
+If gui/load-screen is active, it will be inserted later this frame and prevent
+the viewscreen_loadgamest from working. To work around this, SELECT is fed to
+the screen one frame later.
+]]
+function triggerLoad(loadgame_screen)
+    -- Get rid of child screens (e.g. gui/load-screen)
+    if loadgame_screen.child then
+        local child = loadgame_screen.child
+        while child.child do
+            child = child.child
+        end
+        while child ~= loadgame_screen do
+            child = child.parent
+            dfhack.screen.dismiss(child.child)
+        end
+    end
+
+    gui.simulateInput(loadgame_screen, 'SELECT')
+end
+
+dfhack.timeout(1, 'frames', function() triggerLoad(loadgame_screen) end)