add imgui support

src/gui/PivotGui.cpp

@@ -0,0 +1,52 @@
+#include "PivotGui.h"
+
+#include <imgui.h>
+
+void PivotGui::Init() {}
+
+void PivotGui::Render() {
+
+	ImGuiIO& io = ImGui::GetIO();
+
+	// Our state
+	static bool show_demo_window = true;
+	static bool show_another_window = false;
+	// 1. Show the big demo window (Most of the sample code is in ImGui::ShowDemoWindow()! You can browse its code to learn more about
+	// Dear ImGui!).
+	if (show_demo_window)
+		ImGui::ShowDemoWindow(&show_demo_window);
+
+	// 2. Show a simple window that we create ourselves. We use a Begin/End pair to create a named window.
+	{
+		static float f = 0.0f;
+		static int counter = 0;
+
+		ImGui::Begin("Hello, world!");	// Create a window called "Hello, world!" and append into it.
+
+		ImGui::Text("This is some useful text.");			// Display some text (you can use a format strings too)
+		ImGui::Checkbox("Demo Window", &show_demo_window);	// Edit bools storing our window open/close state
+		ImGui::Checkbox("Another Window", &show_another_window);
+
+		ImGui::SliderFloat("float", &f, 0.0f, 1.0f);  // Edit 1 float using a slider from 0.0f to 1.0f
+
+		if (ImGui::Button("Button"))  // Buttons return true when clicked (most widgets return true when edited/activated)
+			counter++;
+		ImGui::SameLine();
+		ImGui::Text("counter = %d", counter);
+
+		ImGui::Text("Application average %.3f ms/frame (%.1f FPS)", 1000.0f / io.Framerate, io.Framerate);
+		ImGui::End();
+	}
+
+	// 3. Show another simple window.
+	if (show_another_window) {
+		ImGui::Begin("Another Window", &show_another_window);  // Pass a pointer to our bool variable (the window will have a closing
+															   // button that will clear the bool when clicked)
+		ImGui::Text("Hello from another window!");
+		if (ImGui::Button("Close Me"))
+			show_another_window = false;
+		ImGui::End();
+	}
+}
+
+void PivotGui::Destroy() {}