Draw UV gradient

main.zig

@@ -6,8 +6,36 @@ const W = std.unicode.utf8ToUtf16LeStringLiteral;
 pub fn main() void {
     const con_out = uefi.system_table.con_out.?;
     con_out.reset(false) catch unreachable;
-    _ = con_out.outputString(W("Hi :D\r\n")) catch unreachable;
+    _ = con_out.outputString(W("UV gradient incoming...\r\n")) catch unreachable;
 
     const boot_services = uefi.system_table.boot_services.?;
-    boot_services.stall(5 * 1000 * 1000) catch unreachable;
+
+    const graphics = boot_services.locateProtocol(
+        uefi.protocol.GraphicsOutput,
+        null,
+    ) catch null;
+
+    const mode = graphics.?.*.mode;
+    const info = mode.*.info;
+
+    const width = info.horizontal_resolution;
+    const height = info.vertical_resolution;
+
+    var fb: [*]u8 = @ptrFromInt(mode.frame_buffer_base);
+
+    for (0..height) |y| {
+        for (0..width) |x| {
+            const idx = x + width * y;
+            const r: u8 = @truncate(@divTrunc(255 * x, width));
+            const g: u8 = @truncate(@divTrunc(255 * y, height));
+            const b: u8 = 127;
+
+            fb[4 * idx + 0] = b;
+            fb[4 * idx + 1] = g;
+            fb[4 * idx + 2] = r;
+            fb[4 * idx + 3] = 0;
+        }
+    }
+
+    while (true) {}
 }