gui2/game_load: Constrain leader sprites to 72x72 using image path functions

Fixes #3474.

changelog.md

@@ -60,6 +60,7 @@
    * MacOS: Fixed moving the mouse with a touchpad also scrolling GUI dialogs
    * MacOS: Add build number to OS version report
    * Fix layout of Preferences window with some localisations (such as Czech)
+   * Force leader sprites larger than 72x72 to be downscaled in Load Game (issue #3474).
  ### Miscellaneous and bug fixes
    * Fix some minor problems in macOS package
    * Fast Micro AI: Fix bug crashing the AI when units with chance-to-hit

src/gui/dialogs/game_load.cpp

@@ -18,6 +18,7 @@
 
 #include "desktop/open.hpp"
 #include "filesystem.hpp"
+#include "formatter.hpp"
 #include "formula/string_utils.hpp"
 #include "gettext.hpp"
 #include "game_config.hpp"
@@ -172,6 +173,8 @@ void game_load::display_savegame(window& window)
 
 	leader_list.clear();
 
+	const std::string sprite_scale_mod = (formatter() << "~SCALE_INTO(" << game_config::tile_size << ',' << game_config::tile_size << ')').str();
+
 	for(const auto& leader : summary_.child_range("leader")) {
 		widget_data data;
 		widget_item item;
@@ -192,6 +195,9 @@ void game_load::display_savegame(window& window)
 
 		if(leader_image.empty()) {
 			leader_image = "units/unknown-unit.png" + leader["leader_image_tc_modifier"].str();
+		} else {
+			// Scale down any sprites larger than 72x72
+			leader_image += sprite_scale_mod;
 		}
 
 		item["label"] = leader_image;