[Qt] Implement a Qt headless renderer

Using legacy QGLWidget because we support Qt4.

include/mbgl/platform/default/headless_view.hpp

@@ -1,6 +1,9 @@
 #pragma once
 
-#ifdef __APPLE__
+#if defined(__QT__)
+#define MBGL_USE_QT 1
+class QGLWidget;
+#elif defined(__APPLE__)
 #include <TargetConditionals.h>
 #if TARGET_OS_IOS
 #define MBGL_USE_EAGL 1
@@ -63,6 +66,10 @@ private:
     bool extensionsLoaded = false;
     bool active = false;
 
+#if MBGL_USE_QT
+    QGLWidget* glContext = nullptr;
+#endif
+
 #if MBGL_USE_CGL
     CGLContextObj glContext = nullptr;
 #endif

platform/qt/config.cmake

@@ -40,15 +40,20 @@ macro(mbgl_platform_core)
     endif()
 endmacro()
 
-# TODO: Implement a Qt headless view, using offscreen
-# graphics system.
 macro(mbgl_platform_test)
     target_sources(mbgl-test
         PRIVATE test/src/main.cpp
+        PRIVATE platform/qt/test/headless_view_qt.cpp
+        PRIVATE platform/default/headless_display.cpp
+        PRIVATE platform/default/headless_view.cpp
     )
 
     set_source_files_properties(
         test/src/main.cpp
         PROPERTIES COMPILE_FLAGS -DWORK_DIRECTORY="${CMAKE_SOURCE_DIR}"
     )
+
+    target_link_libraries(mbgl-test
+        ${MBGL_QT_LIBRARIES}
+    )
 endmacro()

platform/qt/qt.cmake

@@ -29,10 +29,6 @@ set(MBGL_QT_FILES
     # Misc
     PRIVATE platform/default/log_stderr.cpp
 
-    # Headless headless_view_cgl
-    PRIVATE platform/default/headless_display.cpp
-    PRIVATE platform/default/headless_view.cpp
-
     # Platform integration
     PRIVATE platform/qt/src/async_task.cpp
     PRIVATE platform/qt/src/async_task_impl.hpp
@@ -77,7 +73,6 @@ endif()
 if (CMAKE_HOST_SYSTEM_NAME STREQUAL "Darwin")
     list(APPEND MBGL_QT_FILES
         PRIVATE platform/darwin/src/nsthread.mm
-        PRIVATE platform/darwin/src/headless_view_cgl.cpp
     )
     list(APPEND MBGL_QT_LIBRARIES
         PRIVATE "-framework Foundation"
@@ -86,10 +81,8 @@ if (CMAKE_HOST_SYSTEM_NAME STREQUAL "Darwin")
 else()
     list(APPEND MBGL_QT_FILES
         PRIVATE platform/default/thread.cpp
-        PRIVATE platform/default/headless_view_glx.cpp
     )
     list(APPEND MBGL_QT_LIBRARIES
         PRIVATE -lGL
-        PRIVATE -lX11
     )
 endif()

platform/qt/test/headless_view_qt.cpp

@@ -0,0 +1,106 @@
+#include <mbgl/platform/default/headless_display.hpp>
+#include <mbgl/platform/default/headless_view.hpp>
+
+#include <QApplication>
+#include <QGLContext>
+#include <QGLWidget>
+
+#if QT_VERSION >= 0x050000
+#include <QOpenGLContext>
+#endif
+
+namespace mbgl {
+
+gl::glProc HeadlessView::initializeExtension(const char* name) {
+#if QT_VERSION >= 0x050000
+        QOpenGLContext* thisContext = QOpenGLContext::currentContext();
+        return thisContext->getProcAddress(name);
+#else
+        const QGLContext* thisContext = QGLContext::currentContext();
+        return reinterpret_cast<mbgl::gl::glProc>(thisContext->getProcAddress(name));
+#endif
+}
+
+void HeadlessView::createContext() {
+    static const char* argv[] = { "mbgl" };
+    static int argc = 1;
+    static auto* app = new QApplication(argc, const_cast<char**>(argv));
+
+    Q_UNUSED(app);
+
+    glContext = new QGLWidget;
+}
+
+void HeadlessView::destroyContext() {
+    delete glContext;
+}
+
+void HeadlessView::resizeFramebuffer() {
+    const unsigned int w = dimensions[0] * pixelRatio;
+    const unsigned int h = dimensions[1] * pixelRatio;
+
+    // Create depth/stencil buffer
+    MBGL_CHECK_ERROR(glGenRenderbuffersEXT(1, &fboDepthStencil));
+    MBGL_CHECK_ERROR(glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, fboDepthStencil));
+    MBGL_CHECK_ERROR(glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_DEPTH24_STENCIL8_EXT, w, h));
+    MBGL_CHECK_ERROR(glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, 0));
+
+    MBGL_CHECK_ERROR(glGenRenderbuffersEXT(1, &fboColor));
+    MBGL_CHECK_ERROR(glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, fboColor));
+    MBGL_CHECK_ERROR(glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_RGBA8, w, h));
+    MBGL_CHECK_ERROR(glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, 0));
+
+    MBGL_CHECK_ERROR(glGenFramebuffersEXT(1, &fbo));
+    MBGL_CHECK_ERROR(glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo));
+
+    MBGL_CHECK_ERROR(glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_RENDERBUFFER_EXT, fboColor));
+    MBGL_CHECK_ERROR(glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_STENCIL_ATTACHMENT, GL_RENDERBUFFER_EXT, fboDepthStencil));
+
+    GLenum status = MBGL_CHECK_ERROR(glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT));
+
+    if (status != GL_FRAMEBUFFER_COMPLETE_EXT) {
+        std::string error("Couldn't create framebuffer: ");
+        switch (status) {
+            case GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT_EXT: (error += "incomplete attachment"); break;
+            case GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT_EXT: error += "incomplete missing attachment"; break;
+            case GL_FRAMEBUFFER_INCOMPLETE_DIMENSIONS_EXT: error += "incomplete dimensions"; break;
+            case GL_FRAMEBUFFER_INCOMPLETE_FORMATS_EXT: error += "incomplete formats"; break;
+            case GL_FRAMEBUFFER_INCOMPLETE_DRAW_BUFFER_EXT: error += "incomplete draw buffer"; break;
+            case GL_FRAMEBUFFER_INCOMPLETE_READ_BUFFER_EXT: error += "incomplete read buffer"; break;
+            case GL_FRAMEBUFFER_UNSUPPORTED: error += "unsupported"; break;
+            default: error += "other"; break;
+        }
+        throw std::runtime_error(error);
+    }
+
+    MBGL_CHECK_ERROR(glViewport(0, 0, w, h));
+}
+
+void HeadlessView::clearBuffers() {
+    MBGL_CHECK_ERROR(glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0));
+
+    if (fbo) {
+        MBGL_CHECK_ERROR(glDeleteFramebuffersEXT(1, &fbo));
+        fbo = 0;
+    }
+
+    if (fboColor) {
+        MBGL_CHECK_ERROR(glDeleteRenderbuffersEXT(1, &fboColor));
+        fboColor = 0;
+    }
+
+    if (fboDepthStencil) {
+        MBGL_CHECK_ERROR(glDeleteRenderbuffersEXT(1, &fboDepthStencil));
+        fboDepthStencil = 0;
+    }
+}
+
+void HeadlessView::activateContext() {
+    glContext->makeCurrent();
+}
+
+void HeadlessView::deactivateContext() {
+    glContext->doneCurrent();
+}
+
+} // namespace mbgl