fix: clamp saved window size to minimum size

The stored `vid_last` window size in Launch.cfg (or SimpleGraphic.cfg)
can have a zero window width/height recorded; this typically due to
closing the program while minimized.

As we have a minimum window size enforced in general, adapt the config
loading to clamp the size to the minimum size and safeguard against the
erroneous size and position being stored in the first place.

Author: zao

engine/core/core_video.cpp

@@ -92,6 +92,9 @@ void core_video_c::Apply(bool shown)
 			set.flags|= VID_MAXIMIZE;
 		} else if (vid_resizable->intVal == 3) {
 			if (sscanf(vid_last->strVal.c_str(), "%d,%d,%d,%d,%d", set.save.size + 0, set.save.size + 1, set.save.pos + 0, set.save.pos + 1, (int*)&set.save.maximised) == 5) {
+				// Clamp saved window size as it may be persisted as zero before.
+				set.save.size[0] = (std::max)(CFG_VID_MINWIDTH, set.save.size[0]);
+				set.save.size[1] = (std::max)(CFG_VID_MINHEIGHT, set.save.size[1]);
 				set.flags|= VID_USESAVED;
 			} else {
 				set.flags|= VID_MAXIMIZE;

engine/system/win/sys_video.cpp

@@ -604,15 +604,21 @@ void sys_video_c::FramebufferSizeChanged(int width, int height) {
 
 void sys_video_c::SizeChanged(int width, int height, bool max)
 {
-	vid.size[0] = width;
-	vid.size[1] = height;
-	vid.maximised = max;
+	// Avoid persisting an invalid window size from being minimized.
+	if (!glfwGetWindowAttrib(wnd, GLFW_ICONIFIED)) {
+		vid.size[0] = width;
+		vid.size[1] = height;
+		vid.maximised = max;
+	}
 }
 
 void sys_video_c::PosChanged(int x, int y)
 {
-	vid.pos[0] = x;
-	vid.pos[1] = y;
+	// Avoid persisting an invalid window location from being minimized.
+	if (!glfwGetWindowAttrib(wnd, GLFW_ICONIFIED)) {
+		vid.pos[0] = x;
+		vid.pos[1] = y;
+	}
 }
 
 void sys_video_c::GetMinSize(int& width, int& height)