tweak hide-priority: make toggle state persist across designation menu uses

To reproduce:
1. Enter the `d`esignation menu
2. Press `-+` to change priorities
3. Create a designation
4. Press `Alt-p` to hide priorities
5. Exit and re-enter the designation menu (`Esc`, `d`)

Previously, priorities would be visible again after step 5. With this change, they are not visible until you press `Alt-p` again.

Fixes #1068. Note that this is a relatively unobtrusive fix: selecting a priority with `+-` will still result in priorities being shown again. This is native DF behavior that I am reluctant to override because users of designation priorities likely want to see them.

docs/changelog.txt

@@ -37,6 +37,9 @@ changelog.txt uses a syntax similar to RST, with a few special sequences:
 - `buildingplan`: fixed an issue where planned constructions designated with DF's sizing keys (``umkh``) would sometimes be larger than requested
 - `command-prompt`: fixed issues where overlays created by running certain commands (e.g. `gui/liquids`, `gui/teleport`) would not update the parent screen correctly
 
+## Misc Improvements
+- `tweak` hide-priority: changed so that priorities stay hidden (or visible) when exiting and re-entering the designations menu
+
 ## Lua
 - ``gui.Painter``: fixed error when calling ``viewport()`` method
 - `xlsxreader`: Added Lua class wrappers for the xlsxreader plugin API

plugins/tweak/tweaks/hide-priority.h

@@ -7,6 +7,11 @@ using df::global::ui_sidebar_menus;
 
 struct hide_priority_hook : df::viewscreen_dwarfmodest {
     typedef df::viewscreen_dwarfmodest interpose_base;
+
+    static bool was_valid_mode;
+    static bool toggled_manually;
+    static bool last_show_priorities_setting;
+
     inline bool valid_mode ()
     {
         switch (ui->main.mode)
@@ -35,6 +40,9 @@ struct hide_priority_hook : df::viewscreen_dwarfmodest {
     }
     DEFINE_VMETHOD_INTERPOSE(void, render, ())
     {
+        if (!was_valid_mode && valid_mode() && toggled_manually) {
+            ui_sidebar_menus->designation.priority_set = last_show_priorities_setting;
+        }
         INTERPOSE_NEXT(render)();
         if (valid_mode())
         {
@@ -47,15 +55,24 @@ struct hide_priority_hook : df::viewscreen_dwarfmodest {
                     COLOR_WHITE, COLOR_LIGHTRED);
             }
         }
+        was_valid_mode = valid_mode();
     }
     DEFINE_VMETHOD_INTERPOSE(void, feed, (std::set<df::interface_key> *input))
     {
         if (valid_mode() && input->count(df::interface_key::CUSTOM_ALT_P))
+        {
             ui_sidebar_menus->designation.priority_set = !ui_sidebar_menus->designation.priority_set;
+            toggled_manually = true;
+            last_show_priorities_setting = ui_sidebar_menus->designation.priority_set;
+        }
         else
             INTERPOSE_NEXT(feed)(input);
     }
 };
 
+bool hide_priority_hook::was_valid_mode = false;
+bool hide_priority_hook::toggled_manually = false;
+bool hide_priority_hook::last_show_priorities_setting = false;
+
 IMPLEMENT_VMETHOD_INTERPOSE(hide_priority_hook, feed);
 IMPLEMENT_VMETHOD_INTERPOSE(hide_priority_hook, render);