AP_OSD: added font switching at runtime for SITL

libraries/AP_OSD/AP_OSD_SITL.cpp

@@ -43,7 +43,8 @@ void AP_OSD_SITL::load_font(void)
 {
     uint32_t font_size;
     char fontname[] = "font0.bin";
-    fontname[4] = get_font_num() + '0';
+    last_font = get_font_num();
+    fontname[4] = last_font + '0';
     uint8_t *font_data = AP_ROMFS::find_decompress(fontname, font_size);
     if (font_data == nullptr || font_size != 54 * 256) {
         AP_HAL::panic("Bad font file");
@@ -173,6 +174,9 @@ void AP_OSD_SITL::update_thread(void)
         
         blink = (blink+1) % 4;
         w->display();
+        if (last_font != get_font_num()) {
+            load_font();
+        }
         usleep(10000);
     }
 }

libraries/AP_OSD/AP_OSD_SITL.h

@@ -49,6 +49,7 @@ private:
     sf::RenderWindow *w;
 
     sf::Texture font[256];
+    uint8_t last_font;
 
     // setup to match MAX7456 layout
     static const uint8_t char_width = 12;