[glfw] Reduce memory use when window loses focus

Author: pozdnyakov

platform/glfw/glfw_view.cpp

@@ -102,6 +102,7 @@ GLFWView::GLFWView(bool fullscreen_, bool benchmark_)
     glfwSetFramebufferSizeCallback(window, onFramebufferResize);
     glfwSetScrollCallback(window, onScroll);
     glfwSetKeyCallback(window, onKey);
+    glfwSetWindowFocusCallback(window, onWindowFocus);
 
     glfwGetWindowSize(window, &width, &height);
 
@@ -559,6 +560,13 @@ void GLFWView::onMouseMove(GLFWwindow *window, double x, double y) {
     view->lastY = y;
 }
 
+void GLFWView::onWindowFocus(GLFWwindow *window, int focused) {
+    if (focused == GLFW_FALSE) { // Focus lost.
+        auto *view = reinterpret_cast<GLFWView *>(glfwGetWindowUserPointer(window));
+        view->rendererFrontend->getRenderer()->reduceMemoryUse();
+    }
+}
+
 void GLFWView::run() {
     auto callback = [&] {
         if (glfwWindowShouldClose(window)) {

platform/glfw/glfw_view.hpp

@@ -68,6 +68,7 @@ class GLFWView : public mbgl::MapObserver {
     static void onFramebufferResize(GLFWwindow *window, int width, int height);
     static void onMouseClick(GLFWwindow *window, int button, int action, int modifiers);
     static void onMouseMove(GLFWwindow *window, double x, double y);
+    static void onWindowFocus(GLFWwindow *window, int focused);
 
     // Internal
     void report(float duration);