patch to make norns cairo surfaces interpretable as NV12 frames

diff --git a/matron/src/hardware/screen.c b/matron/src/hardware/screen.c
index 221ca9b4..0ad9aefc 100644
--- a/matron/src/hardware/screen.c
+++ b/matron/src/hardware/screen.c
@@ -88,8 +88,14 @@ static double text_xy[2];
 void screen_init(void) {
     ssd1322_init();
     ssd1322_set_refresh_rate(120);
+    
+    int w = 128, h = 64;
+    cairo_format_t format = CAIRO_FORMAT_A8;
+    uint8_t* buffer = calloc(w * h * 1.5, sizeof(uint8_t));
+    // create chroma plane
+    memset(buffer + w * h, 0x88, w*h/2);
 
-    surface = cairo_image_surface_create(CAIRO_FORMAT_A8, 128, 64);
+    surface = cairo_image_surface_create_for_data(buffer, format, w, h, cairo_format_stride_for_width(format, w));
+    
     cr = cr_primary = cairo_create(surface);
 
     status = FT_Init_FreeType(&value);
@@ -216,6 +222,7 @@ void screen_init(void) {
 
 void screen_deinit(void) {
     ssd1322_deinit();
+    free(cairo_image_surface_get_data(surface));
 
     CHECK_CR
     cairo_destroy(cr);
@@ -633,8 +640,12 @@ void screen_set_operator(int i) {
 screen_surface_t *screen_surface_new(double width, double height) {
     int w = (int)floor(width);
     int h = (int)floor(height);
+
+    uint8_t* buffer = calloc(w * h * 1.5, sizeof(uint8_t));
+    // create chroma plane
+    memset(buffer + w * h, 0x88, w*h/2);
+
     cairo_format_t format = CAIRO_FORMAT_A8;
-    cairo_surface_t *image = cairo_image_surface_create(format, w, h);
+    cairo_surface_t *image = cairo_image_surface_create_for_data(buffer, format, w, h, cairo_format_stride_for_width(format, w));

     cairo_status_t status = cairo_surface_status(image);
     if (status == CAIRO_STATUS_SUCCESS) {
         return (screen_surface_t *)image;
@@ -656,6 +667,7 @@ screen_surface_t *screen_surface_load_png(const char *filename) {
 void screen_surface_free(screen_surface_t *s) {
     CHECK_CR
     // fprintf(stderr, "screen_surface_free(%p)\n", s);
+    free(cairo_image_surface_get_data((cairo_surface_t *)s));
     cairo_surface_destroy((cairo_surface_t *)s);
 }