device,vga: add macro SHOW_SCREEN

src/device/vga.c

@@ -2,6 +2,8 @@
 
 #ifdef HAS_IOE
 
+//#define SHOW_SCREEN
+
 #include "device/map.h"
 #include <SDL2/SDL.h>
 
@@ -15,7 +17,6 @@
 #define SCREEN_W 400
 #define SCREEN_SIZE ((SCREEN_H * SCREEN_W) * sizeof(uint32_t))
 
-static SDL_Window *window = NULL;
 static SDL_Renderer *renderer = NULL;
 static SDL_Texture *texture = NULL;
 
@@ -31,11 +32,15 @@ void update_screen() {
 
 static void vga_io_handler(uint32_t offset, int len, bool is_write) {
   if (offset == 4 && len == 4 && is_write) {
+#ifdef SHOW_SCREEN
     update_screen();
+#endif
   }
 }
 
 void init_vga() {
+#ifdef SHOW_SCREEN
+  SDL_Window *window = NULL;
   char title[128];
   sprintf(title, "%s-NEMU", str(__ISA__));
   SDL_Init(SDL_INIT_VIDEO);
@@ -43,6 +48,7 @@ void init_vga() {
   SDL_SetWindowTitle(window, title);
   texture = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_ARGB8888,
       SDL_TEXTUREACCESS_STATIC, SCREEN_W, SCREEN_H);
+#endif
 
   screensize_port_base = (void *)new_space(8);
   screensize_port_base[0] = ((SCREEN_W) << 16) | (SCREEN_H);