Don't allow screenshots before window is shown

2 files changed, 11 insertions, 2 deletions

diff --git a/ext/ruby2d/ruby2d.c b/ext/ruby2d/ruby2d.c
index 300c8e0..7c17bac 100644
--- a/ext/ruby2d/ruby2d.c
+++ b/ext/ruby2d/ruby2d.c
@@ -176,8 +176,13 @@ static R_VAL ruby2d_ext_screenshot(mrb_state* mrb, R_VAL self) {
 #else
 static R_VAL ruby2d_ext_screenshot(R_VAL self, R_VAL path) {
 #endif
-  S2D_Screenshot(window, RSTRING_PTR(path));
-  return R_NIL;
+  if (window) {
+    S2D_Screenshot(window, RSTRING_PTR(path));
+    return path;
+  } else {
+    S2D_Log(S2D_WARN, "Cannot take screenshot before window is shown");
+    return R_FALSE;
+  }
 }
 
 
diff --git a/test/window_spec.rb b/test/window_spec.rb
index 7be4e2b..7aac7aa 100644
--- a/test/window_spec.rb
+++ b/test/window_spec.rb
@@ -9,4 +9,8 @@ RSpec.describe Ruby2D::Window do
     expect(Window.width).to eq(200)
   end
 
+  it "does not allow screenshots until shown" do
+    expect(Window.screenshot).to be false
+  end
+
 end