RemoveCurrent method for thread context sharing

examples/CMakeLists.txt

@@ -1,6 +1,7 @@
 # All examples depend on Pangolin GUI
 if(BUILD_PANGOLIN_GUI)
     add_subdirectory(HelloPangolin)
+    add_subdirectory(HelloPangolinThreads)
     add_subdirectory(SimpleMultiDisplay)
     add_subdirectory(SimpleDisplayImage)
     add_subdirectory(SimpleScene)

examples/HelloPangolinThreads/CMakeLists.txt

@@ -0,0 +1,6 @@
+# Find Pangolin (https://github.com/stevenlovegrove/Pangolin)
+find_package(Pangolin 0.5 REQUIRED)
+include_directories(${Pangolin_INCLUDE_DIRS})
+
+add_executable(HelloPangolinThreads main.cpp)
+target_link_libraries(HelloPangolinThreads ${Pangolin_LIBRARIES})

examples/HelloPangolinThreads/main.cpp

@@ -0,0 +1,64 @@
+#include <pangolin/pangolin.h>
+#include <thread>
+
+static const std::string window_name = "HelloPangolinThreads";
+
+void setup() {
+    // create a window and bind its context to the main thread
+    pangolin::CreateWindowAndBind(window_name, 640, 480);
+
+    // enable depth
+    glEnable(GL_DEPTH_TEST);
+
+    // unset the current context from the main thread
+    pangolin::GetBoundWindow()->RemoveCurrent();
+}
+
+void run() {
+    // fetch the context and bind it to this thread
+    pangolin::BindToContext(window_name);
+
+    // we manually need to restore the properties of the context
+    glEnable(GL_DEPTH_TEST);
+
+    // Define Projection and initial ModelView matrix
+    pangolin::OpenGlRenderState s_cam(
+        pangolin::ProjectionMatrix(640,480,420,420,320,240,0.2,100),
+        pangolin::ModelViewLookAt(-2,2,-2, 0,0,0, pangolin::AxisY)
+    );
+
+    // Create Interactive View in window
+    pangolin::Handler3D handler(s_cam);
+    pangolin::View& d_cam = pangolin::CreateDisplay()
+            .SetBounds(0.0, 1.0, 0.0, 1.0, -640.0f/480.0f)
+            .SetHandler(&handler);
+
+    while( !pangolin::ShouldQuit() )
+    {
+        // Clear screen and activate view to render into
+        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+        d_cam.Activate(s_cam);
+
+        // Render OpenGL Cube
+        pangolin::glDrawColouredCube();
+
+        // Swap frames and Process Events
+        pangolin::FinishFrame();
+    }
+
+    // unset the current context from the main thread
+    pangolin::GetBoundWindow()->RemoveCurrent();
+}
+
+int main( int /*argc*/, char** /*argv*/ )
+{
+    // create window and context in the main thread
+    setup();
+
+    // use the context in a separate rendering thread
+    std::thread render_loop;
+    render_loop = std::thread(run);
+    render_loop.join();
+
+    return 0;
+}

include/pangolin/display/device/OsxWindow.h

@@ -54,6 +54,8 @@ struct OsxWindow : public PangolinGl
 
     void MakeCurrent() override;
 
+    void RemoveCurrent() override;
+
     void SwapBuffers() override;
 
     void ProcessEvents() override;

include/pangolin/display/device/WinWindow.h

@@ -57,6 +57,8 @@ struct WinWindow : public PangolinGl
 
     void MakeCurrent() override;
 
+    void RemoveCurrent() override;
+
     void SwapBuffers() override;
 
     void ProcessEvents() override;

include/pangolin/display/device/X11Window.h

@@ -89,6 +89,8 @@ struct X11Window : public PangolinGl
 
     void MakeCurrent() override;
 
+    void RemoveCurrent() override;
+
     void SwapBuffers() override;
 
     void ProcessEvents() override;

include/pangolin/display/display_internal.h

@@ -114,6 +114,10 @@ struct PANGOLIN_EXPORT PangolinGl : public WindowInterface
         pango_print_warn("MakeCurrent: Not available with non-pangolin window.\n");
     }
 
+    virtual void RemoveCurrent() override {
+        pango_print_warn("RemoveCurrent: Not available with non-pangolin window.\n");
+    }
+
     virtual void Move(int /*x*/, int /*y*/) override {
         pango_print_warn("Move: Not available with non-pangolin window.\n");
     }

include/pangolin/display/window.h

@@ -45,10 +45,25 @@ class WindowInterface
     virtual ~WindowInterface() {}
 
     virtual void ToggleFullscreen() = 0;
+
     virtual void Move(int x, int y) = 0;
+
     virtual void Resize(unsigned int w, unsigned int h) = 0;
+
+    /**
+     * @brief MakeCurrent set the current context
+     * to be called in a thread before accessing OpenGL
+     */
     virtual void MakeCurrent() = 0;
+
+    /**
+     * @brief RemoveCurrent remove the current context
+     * to be called at the end of a thread
+     */
+    virtual void RemoveCurrent() = 0;
+
     virtual void ProcessEvents() = 0;
+
     virtual void SwapBuffers() = 0;
 };
 

src/display/device/display_osx.mm

@@ -202,6 +202,12 @@ inline void FixOsxFocus()
 void OsxWindow::MakeCurrent()
 {
     [[view openGLContext] makeCurrentContext];
+    context = this;
+}
+
+void OsxWindow::RemoveCurrent()
+{
+    [NSOpenGLContext clearCurrentContext];
 }
 
 void OsxWindow::SwapBuffers()

src/display/device/display_wayland.cpp

@@ -392,6 +392,8 @@ struct WaylandWindow : public PangolinGl
 
     void MakeCurrent() override;
 
+    void RemoveCurrent() override;
+
     void SwapBuffers() override;
 
     void ProcessEvents() override;
@@ -836,6 +838,10 @@ void WaylandWindow::MakeCurrent() {
     context = this;
 }
 
+void WaylandWindow::RemoveCurrent() {
+    eglMakeCurrent(display->egl_display, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
+}
+
 void WaylandWindow::ToggleFullscreen() {
     is_fullscreen = !is_fullscreen;         // state for Pangolin
     display->is_fullscreen = is_fullscreen; // state for Wayland