Implement OpenGL backend in Android viewer app

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2032623002

Review-Url: https://codereview.chromium.org/2032623002

1 files changed, 22 insertions, 3 deletions

diff --git a/tools/viewer/Viewer.cpp b/tools/viewer/Viewer.cpp
index 5228a0fd12..c73b1ba9ce 100644
--- a/tools/viewer/Viewer.cpp
+++ b/tools/viewer/Viewer.cpp
@@ -424,9 +424,11 @@ void Viewer::updateUIState() {
     // We will be able to change the backend too.
     Json::Value backendState(Json::objectValue);
     backendState[kName] = kBackendStateName;
-    backendState[kValue] = fBackendType == sk_app::Window::kVulkan_BackendType ?
-            "Vulkan" : "Other than Vulkan";
+    backendState[kValue] = kBackendTypeStrings[fBackendType];
     backendState[kOptions] = Json::Value(Json::arrayValue);
+    for(auto str : kBackendTypeStrings) {
+        backendState[kOptions].append(Json::Value(str));
+    }
 
     Json::Value state(Json::arrayValue);
     state.append(slideState);
@@ -436,7 +438,10 @@ void Viewer::updateUIState() {
 }
 
 void Viewer::onUIStateChanged(const SkString& stateName, const SkString& stateValue) {
-    // Currently, we only recognize the Slide state
+    // For those who will add more features to handle the state change in this function:
+    // After the change, please call updateUIState no notify the frontend (e.g., Android app).
+    // For example, after slide change, updateUIState is called inside setupCurrentSlide;
+    // after backend change, updateUIState is called in this function.
     if (stateName.equals(kSlideStateName)) {
         int previousSlide = fCurrentSlide;
         fCurrentSlide = 0;
@@ -451,6 +456,20 @@ void Viewer::onUIStateChanged(const SkString& stateName, const SkString& stateVa
             fCurrentSlide = previousSlide;
             SkDebugf("Slide not found: %s", stateValue.c_str());
         }
+    } else if (stateName.equals(kBackendStateName)) {
+        for (int i = 0; i < sk_app::Window::kBackendTypeCount; i++) {
+            if (stateValue.equals(kBackendTypeStrings[i])) {
+                if (fBackendType != i) {
+                    fBackendType = (sk_app::Window::BackendType)i;
+                    fWindow->detach();
+                    fWindow->attach(fBackendType, DisplayParams());
+                    fWindow->inval();
+                    updateTitle();
+                    updateUIState();
+                }
+                break;
+            }
+        }
     } else {
         SkDebugf("Unknown stateName: %s", stateName.c_str());
     }