Adds the function Map::terminate() to allow all GL resources held

by the map to be released immediately.

Map::terminate() will call any GL functions on the current thread
without blocking or defering to the rendering thread.

This function allows a GL context to be destroyed and recreated
safely without having to delete the Map object.

Fixes mapbox/mapbox-gl-native#341

Conflicts:
	include/llmr/renderer/painter.hpp
	test/headless.cpp

2 files changed, 25 insertions, 0 deletions

diff --git a/src/map/map.cpp b/src/map/map.cpp
index de7a7032dc..00f0ac91cc 100644
--- a/src/map/map.cpp
+++ b/src/map/map.cpp
@@ -153,6 +153,12 @@ void Map::cleanup(uv_async_t *async) {
     map->painter.cleanup();
 }
 
+void Map::terminate() {
+    view.make_active();
+    painter.terminate();
+    view.make_inactive();
+}
+
 void Map::render(uv_async_t *async) {
     Map *map = static_cast<Map *>(async->data);
 
diff --git a/src/renderer/painter.cpp b/src/renderer/painter.cpp
index c1705cd7cf..b1522a56b5 100644
--- a/src/renderer/painter.cpp
+++ b/src/renderer/painter.cpp
@@ -82,9 +82,28 @@ void Painter::setupShaders() {
     if (!gaussianShader) gaussianShader = std::make_unique<GaussianShader>();
 }
 
+void Painter::deleteShaders() {
+    plainShader = nullptr;
+    outlineShader = nullptr;
+    lineShader = nullptr;
+    linejoinShader = nullptr;
+    patternShader = nullptr;
+    iconShader = nullptr;
+    rasterShader = nullptr;
+    textShader = nullptr;
+    dotShader = nullptr;
+    compositeShader = nullptr;
+    gaussianShader = nullptr;
+}
+
 void Painter::cleanup() {
 }
 
+void Painter::terminate() {
+    cleanup();
+    deleteShaders();
+}
+
 void Painter::resize() {
     const TransformState &state = map.getState();
     if (gl_viewport != state.getFramebufferDimensions()) {