add EGL backend for headless rendering on linux

CMakeLists.txt

@@ -10,6 +10,7 @@ cmake_policy(SET CMP0054 NEW)   # don't implicitly dereference inside if()
 # Backend
 set(POLYSCOPE_BACKEND_OPENGL3_GLFW "ON" CACHE BOOL "Enable openGL3_glfw backend")
 set(POLYSCOPE_BACKEND_OPENGL_MOCK "ON" CACHE BOOL "Enable openGL_mock backend")
+set(POLYSCOPE_BACKEND_OPENGL3_EGL "AUTO" CACHE STRING "Enable openGL3_egl backend") # 'AUTO' means "if we're on linux and EGL.h is available"
 
 ### Do anything needed for dependencies and bring their stuff in to scope
 add_subdirectory(deps)

include/polyscope/render/engine.h

@@ -439,7 +439,9 @@ class ShaderProgram {
 class Engine {
 
 public:
-  // Options
+
+  Engine();
+  virtual ~Engine();
 
   // High-level control
   virtual void checkError(bool fatal = false) = 0;
@@ -505,13 +507,16 @@ class Engine {
   virtual std::string getClipboardText() = 0;
   virtual void setClipboardText(std::string text) = 0;
 
-  // ImGui
+  // === ImGui
+
+  // NOTE: the imgui backend depends on the window manager (e.g. GLFW), so these must be implemented by the lowest-level concrete engine implementation
   virtual void initializeImGui() = 0;
   virtual void shutdownImGui() = 0;
-  void setImGuiStyle();
-  ImFontAtlas* getImGuiGlobalFontAtlas();
   virtual void ImGuiNewFrame() = 0;
   virtual void ImGuiRender() = 0;
+
+  void setImGuiStyle();
+  ImFontAtlas* getImGuiGlobalFontAtlas();
   virtual void showTextureInImGuiWindow(std::string windowName, TextureBuffer* buffer);
 
 

include/polyscope/render/opengl/gl_engine.h

@@ -6,36 +6,27 @@
 #include "polyscope/render/engine.h"
 #include "polyscope/utilities.h"
 
+#include <unordered_map>
+
+// Note: DO NOT include this header throughout polyscope, and do not directly make openGL calls. This header should only
+// be used to construct an instance of Engine. engine.h gives the render API, all render calls should pass through that.
+
 #ifdef __APPLE__
+// this means this file can only compile openGL on apple if we are also using glfw, but that's fine, because we only
+// ever use the two together on apple
 #define GLFW_INCLUDE_GLCOREARB
 #include "GLFW/glfw3.h"
 #else
 #include "glad/glad.h"
-// glad must come first
-#include "GLFW/glfw3.h"
 #endif
 
 #ifdef _WIN32
 #undef APIENTRY
-#define GLFW_EXPOSE_NATIVE_WIN32
-#define GLFW_EXPOSE_NATIVE_WGL
-#include <GLFW/glfw3native.h>
 #endif
 
-#include "imgui.h"
-#define IMGUI_IMPL_OPENGL_LOADER_GLAD
-#include "backends/imgui_impl_glfw.h"
-#include "backends/imgui_impl_opengl3.h"
-
-#include <unordered_map>
-
-// Note: DO NOT include this header throughout polyscope, and do not directly make openGL calls. This header should only
-// be used to construct an instance of Engine. engine.h gives the render API, all render calls should pass through that.
-
-
 namespace polyscope {
 namespace render {
-namespace backend_openGL3_glfw {
+namespace backend_openGL3 {
 
 // Some very nice typdefs
 typedef GLuint TextureBufferHandle;
@@ -377,12 +368,11 @@ class GLShaderProgram : public ShaderProgram {
 class GLEngine : public Engine {
 public:
   GLEngine();
+  virtual ~GLEngine();
 
   // High-level control
-  void initialize();
   void checkError(bool fatal = false) override;
 
-  void swapDisplayBuffers() override;
   std::vector<unsigned char> readDisplayBuffer() override;
 
   // Manage render state
@@ -391,28 +381,6 @@ class GLEngine : public Engine {
   void setColorMask(std::array<bool, 4> mask = {true, true, true, true}) override;
   void setBackfaceCull(bool newVal) override;
 
-  // === Windowing and framework things
-  void makeContextCurrent() override;
-  void focusWindow() override;
-  void showWindow() override;
-  void hideWindow() override;
-  void updateWindowSize(bool force = false) override;
-  void applyWindowSize() override;
-  void setWindowResizable(bool newVal) override;
-  bool getWindowResizable() override;
-  std::tuple<int, int> getWindowPos() override;
-  bool windowRequestsClose() override;
-  void pollEvents() override;
-  bool isKeyPressed(char c) override; // for lowercase a-z and 0-9 only
-  int getKeyCode(char c) override;    // for lowercase a-z and 0-9 only
-  std::string getClipboardText() override;
-  void setClipboardText(std::string text) override;
-
-  // ImGui
-  void initializeImGui() override;
-  void shutdownImGui() override;
-  void ImGuiNewFrame() override;
-  void ImGuiRender() override;
 
   // === Factory methods
 
@@ -462,9 +430,6 @@ class GLEngine : public Engine {
   // Helpers
   virtual void createSlicePlaneFliterRule(std::string name) override;
 
-  // Internal windowing and engine details
-  GLFWwindow* mainWindow = nullptr;
-
   // Shader program & rule caches
   std::unordered_map<std::string, std::pair<std::vector<ShaderStageSpecification>, DrawMode>> registeredShaderPrograms;
   std::unordered_map<std::string, ShaderReplacementRule> registeredShaderRules;
@@ -478,6 +443,6 @@ class GLEngine : public Engine {
                                                         ShaderReplacementDefaults defaults);
 };
 
-} // namespace backend_openGL3_glfw
+} // namespace backend_openGL3
 } // namespace render
 } // namespace polyscope

include/polyscope/render/opengl/gl_engine_egl.h

@@ -0,0 +1,80 @@
+// Copyright 2017-2023, Nicholas Sharp and the Polyscope contributors. https://polyscope.run
+
+#pragma once
+
+#include "polyscope/options.h"
+#include "polyscope/render/engine.h"
+#include "polyscope/utilities.h"
+
+#ifdef __APPLE__
+#error "EGL backend is not supported on macOS. Disable it in the CMake build options."
+#else
+#include "glad/glad.h"
+// glad must come first
+#include <EGL/egl.h>
+#endif
+
+
+#include "imgui.h"
+
+#include "polyscope/render/opengl/gl_engine.h"
+
+#include <unordered_map>
+
+// Note: DO NOT include this header throughout polyscope, and do not directly make openGL calls. This header should only
+// be used to construct an instance of Engine. engine.h gives the render API, all render calls should pass through that.
+
+
+namespace polyscope {
+namespace render {
+namespace backend_openGL3 {
+
+
+class GLEngineEGL : public GLEngine {
+
+public:
+  GLEngineEGL();
+  virtual ~GLEngineEGL();
+
+  // High-level control
+  void initialize();
+  void swapDisplayBuffers() override;
+  void checkError(bool fatal = false) override;
+
+  // === Windowing and framework things
+
+  void makeContextCurrent() override;
+  void pollEvents() override;
+
+  void focusWindow() override;
+  void showWindow() override;
+  void hideWindow() override;
+  void updateWindowSize(bool force = false) override;
+  void applyWindowSize() override;
+  void setWindowResizable(bool newVal) override;
+  bool getWindowResizable() override;
+  std::tuple<int, int> getWindowPos() override;
+  bool windowRequestsClose() override;
+
+  bool isKeyPressed(char c) override; // for lowercase a-z and 0-9 only
+  int getKeyCode(char c) override;    // for lowercase a-z and 0-9 only
+  std::string getClipboardText() override;
+  void setClipboardText(std::string text) override;
+
+
+  // === ImGui
+
+  void initializeImGui() override;
+  void shutdownImGui() override;
+  void ImGuiNewFrame() override;
+  void ImGuiRender() override;
+
+protected:
+  // Internal windowing and engine details
+  EGLDisplay eglDisplay;
+  EGLContext eglContext;
+};
+
+} // namespace backend_openGL3
+} // namespace render
+} // namespace polyscope

include/polyscope/render/opengl/gl_engine_glfw.h

@@ -0,0 +1,91 @@
+// Copyright 2017-2023, Nicholas Sharp and the Polyscope contributors. https://polyscope.run
+
+#pragma once
+
+#include "polyscope/options.h"
+#include "polyscope/render/engine.h"
+#include "polyscope/utilities.h"
+
+#ifdef __APPLE__
+#define GLFW_INCLUDE_GLCOREARB
+#include "GLFW/glfw3.h"
+#else
+#include "glad/glad.h"
+// glad must come first
+#include "GLFW/glfw3.h"
+#endif
+
+#ifdef _WIN32
+#undef APIENTRY
+#define GLFW_EXPOSE_NATIVE_WIN32
+#define GLFW_EXPOSE_NATIVE_WGL
+#include <GLFW/glfw3native.h>
+#endif
+
+#include "imgui.h"
+#define IMGUI_IMPL_OPENGL_LOADER_GLAD
+#include "backends/imgui_impl_glfw.h"
+#include "backends/imgui_impl_opengl3.h"
+
+#include "polyscope/render/opengl/gl_engine.h"
+
+#include <unordered_map>
+
+// Note: DO NOT include this header throughout polyscope, and do not directly make openGL calls. This header should only
+// be used to construct an instance of Engine. engine.h gives the render API, all render calls should pass through that.
+
+
+namespace polyscope {
+namespace render {
+namespace backend_openGL3 {
+
+
+class GLEngineGLFW : public GLEngine {
+
+public:
+
+  GLEngineGLFW();
+  virtual ~GLEngineGLFW();
+
+  // High-level control
+  void initialize();
+  void swapDisplayBuffers() override;
+
+  // === Windowing and framework things
+
+  void makeContextCurrent() override;
+  void pollEvents() override;
+
+  void focusWindow() override;
+  void showWindow() override;
+  void hideWindow() override;
+  void updateWindowSize(bool force = false) override;
+  void applyWindowSize() override;
+  void setWindowResizable(bool newVal) override;
+  bool getWindowResizable() override;
+  std::tuple<int, int> getWindowPos() override;
+  bool windowRequestsClose() override;
+
+  bool isKeyPressed(char c) override; // for lowercase a-z and 0-9 only
+  int getKeyCode(char c) override;    // for lowercase a-z and 0-9 only
+  std::string getClipboardText() override;
+  void setClipboardText(std::string text) override;
+
+
+  // === ImGui
+
+  void initializeImGui() override;
+  void shutdownImGui() override;
+  void ImGuiNewFrame() override;
+  void ImGuiRender() override;
+
+protected:
+
+  // Internal windowing and engine details
+  GLFWwindow* mainWindow = nullptr;
+
+};
+
+} // namespace backend_openGL3
+} // namespace render
+} // namespace polyscope

include/polyscope/render/opengl/shaders/common.h

@@ -8,10 +8,10 @@
 
 namespace polyscope {
 namespace render {
-namespace backend_openGL3_glfw {
+namespace backend_openGL3 {
 
 extern const char* shaderCommonSource;
 
-} // namespace backend_openGL3_glfw
+} // namespace backend_openGL3
 } // namespace render
 } // namespace polyscope

include/polyscope/render/opengl/shaders/cylinder_shaders.h

@@ -6,7 +6,7 @@
 
 namespace polyscope {
 namespace render {
-namespace backend_openGL3_glfw {
+namespace backend_openGL3 {
 
 // High level pipeline
 extern const ShaderStageSpecification FLEX_CYLINDER_VERT_SHADER;
@@ -23,6 +23,6 @@ extern const ShaderReplacementRule CYLINDER_CULLPOS_FROM_MID;
 extern const ShaderReplacementRule CYLINDER_VARIABLE_SIZE;
 
 
-} // namespace backend_openGL3_glfw
+} // namespace backend_openGL3
 } // namespace render
 } // namespace polyscope

include/polyscope/render/opengl/shaders/gizmo_shaders.h

@@ -6,7 +6,7 @@
 
 namespace polyscope {
 namespace render {
-namespace backend_openGL3_glfw {
+namespace backend_openGL3 {
 
 // Stages
 extern const ShaderStageSpecification TRANSFORMATION_GIZMO_ROT_VERT;
@@ -17,6 +17,6 @@ extern const ShaderStageSpecification SLICE_PLANE_FRAG_SHADER;
 // Rules
 extern const ShaderReplacementRule TRANSFORMATION_GIZMO_VEC;
 
-} // namespace backend_openGL3_glfw
+} // namespace backend_openGL3
 } // namespace render
 } // namespace polyscope

include/polyscope/render/opengl/shaders/grid_shaders.h

@@ -6,7 +6,7 @@
 
 namespace polyscope {
 namespace render {
-namespace backend_openGL3_glfw {
+namespace backend_openGL3 {
 
 // High level pipeline
 extern const ShaderStageSpecification FLEX_GRIDCUBE_VERT_SHADER;
@@ -24,6 +24,6 @@ extern const ShaderReplacementRule GRIDCUBE_CONSTANT_PICK;
 extern const ShaderReplacementRule GRIDCUBE_CULLPOS_FROM_CENTER;
 
 
-} // namespace backend_openGL3_glfw
+} // namespace backend_openGL3
 } // namespace render
 } // namespace polyscope

include/polyscope/render/opengl/shaders/ground_plane_shaders.h

@@ -6,7 +6,7 @@
 
 namespace polyscope {
 namespace render {
-namespace backend_openGL3_glfw {
+namespace backend_openGL3 {
 
 extern const ShaderStageSpecification GROUND_PLANE_VERT_SHADER;
 extern const ShaderStageSpecification GROUND_PLANE_TILE_FRAG_SHADER;
@@ -16,6 +16,6 @@ extern const ShaderStageSpecification GROUND_PLANE_SHADOW_FRAG_SHADER;
 // Rules
 // extern const ShaderReplacementRule RULE_NAME;
 
-} // namespace backend_openGL3_glfw
+} // namespace backend_openGL3
 } // namespace render
 } // namespace polyscope