Samples: Add command line flag to select renderer.

This gives us the ability to test Vulkan without a special recompile,
and keeps the default setting to the default ANGLE renderer. Only
implemented for the hello_triangle sample currently.

Also includes an extra error message for missing EGL config, which is
where the Vulkan init fails right now, due to missing depth/stencil
support.

Also includes a hack to get Vulkan samples running without depth/
stencil.

BUG=angleproject:2167

Change-Id: I6925b9b84956fb69cbf602a828ea95d8c7125b68
Reviewed-on: https://chromium-review.googlesource.com/707688
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>

samples/hello_triangle/HelloTriangle.cpp

@@ -19,8 +19,8 @@
 class HelloTriangleSample : public SampleApplication
 {
   public:
-    HelloTriangleSample()
-        : SampleApplication("HelloTriangle", 1280, 720)
+    HelloTriangleSample(EGLint displayType)
+        : SampleApplication("HelloTriangle", 1280, 720, 2, 0, displayType)
     {
     }
 
@@ -87,6 +87,13 @@ class HelloTriangleSample : public SampleApplication
 
 int main(int argc, char **argv)
 {
-    HelloTriangleSample app;
+    EGLint displayType = EGL_PLATFORM_ANGLE_TYPE_DEFAULT_ANGLE;
+
+    if (argc > 1)
+    {
+        displayType = GetDisplayTypeFromArg(argv[1]);
+    }
+
+    HelloTriangleSample app(displayType);
     return app.run();
 }

samples/sample_util/SampleApplication.cpp

@@ -8,6 +8,20 @@
 #include "EGLWindow.h"
 #include "random_utils.h"
 
+#include "angle_gl.h"
+
+#include <iostream>
+
+namespace
+{
+using DisplayTypeInfo = std::pair<const char *, EGLint>;
+
+constexpr DisplayTypeInfo kDisplayTypes[] = {
+    {"d3d9", EGL_PLATFORM_ANGLE_TYPE_D3D9_ANGLE}, {"d3d11", EGL_PLATFORM_ANGLE_TYPE_D3D11_ANGLE},
+    {"gl", EGL_PLATFORM_ANGLE_TYPE_OPENGL_ANGLE}, {"gles", EGL_PLATFORM_ANGLE_TYPE_OPENGLES_ANGLE},
+    {"null", EGL_PLATFORM_ANGLE_TYPE_NULL_ANGLE}, {"vulkan", EGL_PLATFORM_ANGLE_TYPE_VULKAN_ANGLE}};
+}  // anonymous namespace
+
 SampleApplication::SampleApplication(const std::string &name,
                                      size_t width,
                                      size_t height,
@@ -25,8 +39,19 @@ SampleApplication::SampleApplication(const std::string &name,
     mEGLWindow->setConfigGreenBits(8);
     mEGLWindow->setConfigBlueBits(8);
     mEGLWindow->setConfigAlphaBits(8);
-    mEGLWindow->setConfigDepthBits(24);
-    mEGLWindow->setConfigStencilBits(8);
+
+    // The Vulkan back-end currently does not support depth/stencil.
+    // TODO(jmadill): Remove this hack once Vulkan supports more configs.
+    if (requestedRenderer == EGL_PLATFORM_ANGLE_TYPE_VULKAN_ANGLE)
+    {
+        mEGLWindow->setConfigDepthBits(0);
+        mEGLWindow->setConfigStencilBits(0);
+    }
+    else
+    {
+        mEGLWindow->setConfigDepthBits(24);
+        mEGLWindow->setConfigStencilBits(8);
+    }
 
     // Disable vsync
     mEGLWindow->setSwapInterval(0);
@@ -156,3 +181,17 @@ bool SampleApplication::popEvent(Event *event)
 {
     return mOSWindow->popEvent(event);
 }
+
+EGLint GetDisplayTypeFromArg(const char *displayTypeArg)
+{
+    for (const auto &displayTypeInfo : kDisplayTypes)
+    {
+        if (strcmp(displayTypeInfo.first, displayTypeArg) == 0)
+        {
+            return displayTypeInfo.second;
+        }
+    }
+
+    std::cout << "Unknown ANGLE back-end API: " << displayTypeArg << std::endl;
+    return EGL_PLATFORM_ANGLE_TYPE_DEFAULT_ANGLE;
+}

samples/sample_util/SampleApplication.h

@@ -61,4 +61,6 @@ class SampleApplication
     std::unique_ptr<OSWindow> mOSWindow;
 };
 
+EGLint GetDisplayTypeFromArg(const char *displayTypeArg);
+
 #endif // SAMPLE_UTIL_SAMPLE_APPLICATION_H

util/EGLWindow.cpp

@@ -6,6 +6,7 @@
 
 #include <string.h>
 #include <cassert>
+#include <iostream>
 #include <vector>
 
 #include "EGLWindow.h"
@@ -258,6 +259,7 @@ bool EGLWindow::initializeDisplayAndSurface(OSWindow *osWindow)
 
     if (!FindEGLConfig(mDisplay, configAttributes.data(), &mConfig))
     {
+        std::cout << "Could not find a suitable EGL config!" << std::endl;
         destroyGL();
         return false;
     }