Force a full redraw on resize events.

This fixes the worst of the resize-related artefacts during gameplay
by forcing a full redraw on every resize event. These changes will be
revisited as a part of #23934.

src/gui/widgets/window.cpp

@@ -1446,7 +1446,7 @@ void twindow::signal_handler_sdl_video_resize(const event::tevent event,
 											  const tpoint& new_size)
 {
 	DBG_GUI_E << LOG_HEADER << ' ' << event << ".\n";
-
+#if !SDL_VERSION_ATLEAST(2, 0, 0)
 	if(new_size.x < preferences::min_allowed_width()
 	   || new_size.y < preferences::min_allowed_height()) {
 
@@ -1461,6 +1461,7 @@ void twindow::signal_handler_sdl_video_resize(const event::tevent event,
 		handled = true;
 		return;
 	}
+#endif
 
 	if(!preferences::set_resolution(video_, new_size.x, new_size.y)) {
 

src/preferences_display.cpp

@@ -176,11 +176,13 @@ bool set_resolution(CVideo& video
 	int bpp = video.bppForMode(width, height, flags);
 
 	if(bpp != 0) {
-		video.setMode(width, height, bpp, flags);
+		//video.setMode(width, height, bpp, flags);
 
+#if !SDL_VERSION_ATLEAST(2, 0, 0)
 		if(disp) {
 			disp->redraw_everything();
 		}
+#endif
 
 	} else {
         // grzywacz: is this even true?

src/video.cpp

@@ -30,6 +30,7 @@
 #include "sdl/window.hpp"
 #include "video.hpp"
 #include "sdl/gpu.hpp"
+#include "display.hpp"
 
 #include <boost/foreach.hpp>
 
@@ -47,11 +48,18 @@ namespace {
 	GPU_Target *render_target_;
 }
 void resize_monitor::process(events::pump_info &info) {
+#if !SDL_VERSION_ATLEAST(2, 0, 0)
 	if(info.resize_dimensions.first >= preferences::min_allowed_width()
 	&& info.resize_dimensions.second >= preferences::min_allowed_height()
 	&& disallow_resize == 0) {
 		preferences::set_resolution(info.resize_dimensions);
 	}
+#else
+	if(info.resize_dimensions.first > 0 &&
+			info.resize_dimensions.second > 0
+			&& display::get_singleton())
+		display::get_singleton()->redraw_everything();
+#endif
 }
 
 resize_lock::resize_lock()