Add function to wait for VGA's vsync

4 files changed, 8 insertions, 2 deletions

diff --git a/TODO.md b/TODO.md
index a1ccdc3..7715c19 100644
--- a/TODO.md
+++ b/TODO.md
@@ -3,7 +3,6 @@
 - drawing
   - sw blitter
 - time
-  - vga vsync
   - tick counter
 - input
   - keyboard
@@ -16,7 +15,6 @@
   - MOD player?
   - ADLIB music?
 - data (embedded in EXE)
-  - image data: PNG
   - map data: JSON
 - screens
   - menu
diff --git a/src/main.c b/src/main.c
index a8a6b77..2b01d3f 100644
--- a/src/main.c
+++ b/src/main.c
@@ -24,6 +24,7 @@ int main(int argc, char *argv[])
 
     for (int i = 0; i < 16; i++)
     {
+        wait_vsync();
         memset(screen, i, 320 * 200);
         getch();
     }
diff --git a/src/vga.c b/src/vga.c
index a6524bd..981ad6f 100644
--- a/src/vga.c
+++ b/src/vga.c
@@ -24,6 +24,12 @@ void set_mode(uint8_t mode)
     __dpmi_int(0x10, &regs);
 }
 
+void wait_vsync()
+{
+    while (inportb(0x3da) & 8);
+    while (!(inportb(0x3da) & 8));
+}
+
 void set_palette(const uint8_t *palette)
 {
     outportb(0x3c8, 0);
diff --git a/src/vga.h b/src/vga.h
index a9c46c6..2332413 100644
--- a/src/vga.h
+++ b/src/vga.h
@@ -5,6 +5,7 @@ uint8_t *open_framebuffer();
 void close_framebuffer();
 
 void set_mode(uint8_t mode);
+void wait_vsync();
 
 /* the palette is expected to be 8 bit per color, and will be converted to VGA's 6 bit per color */
 void set_palette(const uint8_t *palette);