fix imgui init calls for non-GLFW backends

Author: nmwsharp

include/polyscope/render/mock_opengl/mock_gl_engine.h

@@ -358,6 +358,7 @@ class MockGLEngine : public Engine {
 
   // ImGui
   void initializeImGui() override;
+  void configureImGui() override;
   void shutdownImGui() override;
   void ImGuiNewFrame() override;
   void ImGuiRender() override;

include/polyscope/render/opengl/gl_engine_egl.h

@@ -69,6 +69,7 @@ class GLEngineEGL : public GLEngine {
   // === ImGui
 
   void initializeImGui() override;
+  void configureImGui() override;
   void shutdownImGui() override;
   void ImGuiNewFrame() override;
   void ImGuiRender() override;

src/render/mock_opengl/mock_gl_engine.cpp

@@ -1562,7 +1562,7 @@ void MockGLEngine::initialize() {
   GLFrameBuffer* glScreenBuffer = new GLFrameBuffer(view::bufferWidth, view::bufferHeight, true);
   displayBuffer.reset(glScreenBuffer);
 
-  if(options::uiScale < 0) { // only set from system if the value is -1, meaning not set yet
+  if (options::uiScale < 0) { // only set from system if the value is -1, meaning not set yet
     options::uiScale = 1.;
   }
 
@@ -1581,6 +1581,19 @@ void MockGLEngine::initializeImGui() {
   configureImGui();
 }
 
+void MockGLEngine::configureImGui() {
+  
+  // don't both calling the style callbacks, there is no UI
+
+  if (options::uiScale < 0) {
+    exception("uiScale is < 0. Perhaps it wasn't initialized?");
+  }
+
+  ImGuiIO& io = ImGui::GetIO();
+  io.Fonts->Clear();
+  io.Fonts->Build();
+}
+
 void MockGLEngine::shutdown() {
   checkError();
   shutdownImGui();

src/render/opengl/gl_engine_egl.cpp

@@ -436,6 +436,19 @@ void GLEngineEGL::initializeImGui() {
   configureImGui();
 }
 
+void GLEngineEGL::configureImGui() {
+
+  // don't both calling the style callbacks, there is no UI
+
+  if (options::uiScale < 0) {
+    exception("uiScale is < 0. Perhaps it wasn't initialized?");
+  }
+
+  ImGuiIO& io = ImGui::GetIO();
+  io.Fonts->Clear();
+  io.Fonts->Build();
+}
+
 void GLEngineEGL::shutdown() {
   checkError();
   shutdownImGui();