add mirror option to debug video tap

src/debug_video_tap.cpp

@@ -160,13 +160,19 @@ float DebugVideoTap::render(void) {
 			ImGui::EndCombo();
 		}
 
+		//ImGui::SetNextItemWidth(0);
+		ImGui::Checkbox("mirror", &_mirror);
+
 		// img here
 		if (_tex != 0) {
+			ImGui::SameLine();
 			ImGui::Text("moving avg interval: %f", _v_interval_avg);
 			const float img_w = ImGui::GetContentRegionAvail().x;
 			ImGui::Image(
 				reinterpret_cast<ImTextureID>(_tex),
-				ImVec2{img_w, img_w * float(_tex_h)/_tex_w}
+				ImVec2{img_w, img_w * float(_tex_h)/_tex_w},
+				ImVec2{_mirror?1.f:0.f, 0},
+				ImVec2{_mirror?0.f:1.f, 1}
 			);
 		}
 	}

src/debug_video_tap.hpp

@@ -18,6 +18,8 @@ class DebugVideoTap {
 	uint32_t _tex_w {0};
 	uint32_t _tex_h {0};
 
+	bool _mirror {false}; // flip horizontally
+
 	uint64_t _v_last_ts {0}; // us
 	float _v_interval_avg {0.f}; // s