embed/unix: save screenshot on "P" press in emulator

embed/extmod/modtrezorui/display-unix.h

@@ -163,6 +163,7 @@ void display_save(const char *prefix)
     char fname[256];
     snprintf(fname, sizeof(fname), "%s%08d.png", prefix, cnt);
     IMG_SavePNG(BUFFER, fname);
+    fprintf(stderr, "Saved display buffer to %s\n", fname);
     cnt++;
 #endif
 }

embed/unix/touch.c

@@ -28,6 +28,7 @@ extern int sdl_display_res_x, sdl_display_res_y;
 extern int sdl_touch_offset_x, sdl_touch_offset_y;
 
 extern void __shutdown(void);
+extern void display_save(const char *prefix);
 
 uint32_t touch_read(void)
 {
@@ -69,6 +70,9 @@ uint32_t touch_read(void)
                 if (event.key.keysym.sym == SDLK_ESCAPE) {
                     __shutdown();
                 }
+                if (event.key.keysym.sym == SDLK_p) {
+                    display_save("emu");
+                }
                 break;
             case SDL_QUIT:
                 __shutdown();