6 files changed, 227 insertions, 0 deletions
diff --git a/platform/default/mbgl/gl/headless_backend.cpp b/platform/default/mbgl/gl/headless_backend.cpp
new file mode 100644
index 0000000000..0bfdf11c98
--- /dev/null
+++ b/platform/default/mbgl/gl/headless_backend.cpp
@@ -0,0 +1,72 @@
+#include <mbgl/gl/headless_backend.hpp>
+#include <mbgl/gl/headless_display.hpp>
+
+#include <cassert>
+#include <stdexcept>
+#include <type_traits>
+
+namespace mbgl {
+
+HeadlessBackend::HeadlessBackend() {
+    activate();
+}
+
+HeadlessBackend::HeadlessBackend(std::shared_ptr<HeadlessDisplay> display_)
+        : display(std::move(display_)) {
+    activate();
+}
+
+HeadlessBackend::~HeadlessBackend() {
+    deactivate();
+    destroyContext();
+}
+
+void HeadlessBackend::activate() {
+    active = true;
+
+    if (!hasContext()) {
+        if (!hasDisplay()) {
+            throw std::runtime_error("Display is not set");
+        }
+        createContext();
+    }
+
+    activateContext();
+
+    if (!extensionsLoaded) {
+        gl::InitializeExtensions(initializeExtension);
+        extensionsLoaded = true;
+    }
+}
+
+void HeadlessBackend::deactivate() {
+    deactivateContext();
+    active = false;
+}
+
+void HeadlessBackend::invalidate() {
+    assert(false);
+}
+
+void HeadlessBackend::destroyContext() {
+    assert(hasContext());
+    impl.reset();
+}
+
+void HeadlessBackend::activateContext() {
+    assert(hasContext());
+    impl->activateContext();
+}
+
+void HeadlessBackend::deactivateContext() {
+    assert(hasContext());
+    impl->deactivateContext();
+}
+
+void HeadlessBackend::notifyMapChange(MapChange change) {
+    if (mapChangeCallback) {
+        mapChangeCallback(change);
+    }
+}
+
+} // namespace mbgl
diff --git a/platform/default/mbgl/gl/headless_backend.hpp b/platform/default/mbgl/gl/headless_backend.hpp
new file mode 100644
index 0000000000..da8c55e044
--- /dev/null
+++ b/platform/default/mbgl/gl/headless_backend.hpp
@@ -0,0 +1,57 @@
+#pragma once
+
+#include <mbgl/gl/extension.hpp>
+
+#include <mbgl/map/backend.hpp>
+
+#include <memory>
+#include <functional>
+
+namespace mbgl {
+
+class HeadlessDisplay;
+
+class HeadlessBackend : public Backend {
+public:
+    HeadlessBackend();
+    HeadlessBackend(std::shared_ptr<HeadlessDisplay>);
+    ~HeadlessBackend() override;
+
+    void invalidate() override;
+    void activate() override;
+    void deactivate() override;
+    void notifyMapChange(MapChange) override;
+
+    void setMapChangeCallback(std::function<void(MapChange)>&& cb) { mapChangeCallback = std::move(cb); }
+
+    struct Impl {
+        virtual ~Impl() {}
+        virtual void activateContext() = 0;
+        virtual void deactivateContext() {}
+    };
+
+private:
+    // Implementation specific functions
+    static gl::glProc initializeExtension(const char*);
+
+    bool hasContext() const { return bool(impl); }
+    bool hasDisplay();
+
+    void createContext();
+
+private:
+    void destroyContext();
+
+    void activateContext();
+    void deactivateContext();
+
+    std::unique_ptr<Impl> impl;
+    std::shared_ptr<HeadlessDisplay> display;
+
+    bool extensionsLoaded = false;
+    bool active = false;
+
+    std::function<void(MapChange)> mapChangeCallback;
+};
+
+} // namespace mbgl
diff --git a/platform/default/mbgl/gl/headless_display.cpp b/platform/default/mbgl/gl/headless_display.cpp
new file mode 100644
index 0000000000..6247046c29
--- /dev/null
+++ b/platform/default/mbgl/gl/headless_display.cpp
@@ -0,0 +1,15 @@
+#include <mbgl/gl/headless_display.hpp>
+
+namespace mbgl {
+
+class HeadlessDisplay::Impl {};
+
+HeadlessDisplay::HeadlessDisplay() {
+    // no-op
+}
+
+HeadlessDisplay::~HeadlessDisplay() {
+    // no-op
+}
+
+} // namespace mbgl
diff --git a/platform/default/mbgl/gl/headless_display.hpp b/platform/default/mbgl/gl/headless_display.hpp
new file mode 100644
index 0000000000..a5c95085b8
--- /dev/null
+++ b/platform/default/mbgl/gl/headless_display.hpp
@@ -0,0 +1,20 @@
+#pragma once
+
+#include <memory>
+
+namespace mbgl {
+
+class HeadlessDisplay {
+public:
+    HeadlessDisplay();
+    ~HeadlessDisplay();
+
+    template <typename DisplayAttribute>
+    DisplayAttribute attribute() const;
+
+private:
+    class Impl;
+    std::unique_ptr<Impl>  impl;
+};
+
+} // namespace mbgl
diff --git a/platform/default/mbgl/gl/offscreen_view.cpp b/platform/default/mbgl/gl/offscreen_view.cpp
new file mode 100644
index 0000000000..16faf6a4a9
--- /dev/null
+++ b/platform/default/mbgl/gl/offscreen_view.cpp
@@ -0,0 +1,30 @@
+#include <mbgl/gl/offscreen_view.hpp>
+#include <mbgl/gl/context.hpp>
+
+#include <cstring>
+#include <cassert>
+
+namespace mbgl {
+
+OffscreenView::OffscreenView(gl::Context& context_, const Size size_)
+    : size(std::move(size_)), context(context_) {
+    assert(size);
+}
+
+void OffscreenView::bind() {
+    if (!framebuffer) {
+        color = context.createRenderbuffer<gl::RenderbufferType::RGBA>(size);
+        depthStencil = context.createRenderbuffer<gl::RenderbufferType::DepthStencil>(size);
+        framebuffer = context.createFramebuffer(*color, *depthStencil);
+    } else {
+        context.bindFramebuffer = framebuffer->framebuffer;
+    }
+
+    context.viewport = { 0, 0, size };
+}
+
+PremultipliedImage OffscreenView::readStillImage() {
+    return context.readFramebuffer<PremultipliedImage>(size);
+}
+
+} // namespace mbgl
diff --git a/platform/default/mbgl/gl/offscreen_view.hpp b/platform/default/mbgl/gl/offscreen_view.hpp
new file mode 100644
index 0000000000..0e839e14cc
--- /dev/null
+++ b/platform/default/mbgl/gl/offscreen_view.hpp
@@ -0,0 +1,33 @@
+#pragma once
+
+#include <mbgl/map/view.hpp>
+#include <mbgl/gl/framebuffer.hpp>
+#include <mbgl/gl/renderbuffer.hpp>
+#include <mbgl/util/optional.hpp>
+#include <mbgl/util/image.hpp>
+
+namespace mbgl {
+
+namespace gl {
+class Context;
+} // namespace gl
+
+class OffscreenView : public View {
+public:
+    OffscreenView(gl::Context&, Size size = { 256, 256 });
+
+    void bind() override;
+
+    PremultipliedImage readStillImage();
+
+public:
+    const Size size;
+
+private:
+    gl::Context& context;
+    optional<gl::Framebuffer> framebuffer;
+    optional<gl::Renderbuffer<gl::RenderbufferType::RGBA>> color;
+    optional<gl::Renderbuffer<gl::RenderbufferType::DepthStencil>> depthStencil;
+};
+
+} // namespace mbgl