Some more improvements/fixes to the VulkanViewer

tools/vulkan/viewer/VulkanViewer.cpp

Index: tools/vulkan/viewer/VulkanViewer.cpp
diff --git a/tools/vulkan/viewer/VulkanViewer.cpp b/tools/vulkan/viewer/VulkanViewer.cpp
index 27e7b1c08253a7d51cee623956dcab2276d389da..5c6e780f95c4044ff7c49ead1cb96e10485c0cf0 100644
--- a/tools/vulkan/viewer/VulkanViewer.cpp
+++ b/tools/vulkan/viewer/VulkanViewer.cpp
@@ -31,8 +31,10 @@ static void on_paint_handler(SkCanvas* canvas, void* userData) {
     return vv->onPaint(canvas);
 }
 
-VulkanViewer::VulkanViewer(int argc, char** argv, void* platformData) :
-    fGMs(skiagm::GMRegistry::Head()){
+VulkanViewer::VulkanViewer(int argc, char** argv, void* platformData)
+    : fGMs(skiagm::GMRegistry::Head())
+    , fCurrentMeasurement(0) {
+    memset(fMeasurements, 0, sizeof(fMeasurements));
 
     fWindow = Window::CreateNativeWindow(platformData);
     fWindow->attach(Window::kVulkan_BackendType, 0, nullptr);
@@ -41,7 +43,10 @@ VulkanViewer::VulkanViewer(int argc, char** argv, void* platformData) :
     fWindow->registerKeyFunc(on_key_handler, this);
     fWindow->registerPaintFunc(on_paint_handler, this);
 
-    fWindow->setTitle("VulkanViewer");
+    SkAutoTDelete<skiagm::GM> gm(fGMs->factory()(nullptr));
+    SkString title("VulkanViewer: ");
+    title.append(gm->getName());
+    fWindow->setTitle(title.c_str());
     fWindow->show();
 }
 
@@ -54,7 +59,11 @@ bool VulkanViewer::onKey(Window::Key key, Window::InputState state, uint32_t mod
     if (Window::kDown_InputState == state && (modifiers & Window::kFirstPress_ModifierKey) &&
         key == Window::kRight_Key) {
         fGMs = fGMs->next();
-    } 
+        SkAutoTDelete<skiagm::GM> gm(fGMs->factory()(nullptr));
+        SkString title("VulkanViewer: ");
+        title.append(gm->getName());
+        fWindow->setTitle(title.c_str());
+    }
 
     return true;
 }
@@ -63,12 +72,59 @@ void VulkanViewer::onPaint(SkCanvas* canvas) {
     SkAutoTDelete<skiagm::GM> gm(fGMs->factory()(nullptr));
 
     canvas->save();
-
     gm->draw(canvas);
+    canvas->restore();
+
+    drawStats(canvas);
+}
+
+void VulkanViewer::drawStats(SkCanvas* canvas) {
+    static const float kPixelPerMS = 2.0f;
+    static const int kDisplayWidth = 130;
+    static const int kDisplayHeight = 100;
+    static const int kDisplayPadding = 10;
+    static const int kGraphPadding = 3;
+    static const SkScalar kBaseMS = 1000.f / 60.f;  // ms/frame to hit 60 fps
+
+    SkISize canvasSize = canvas->getDeviceSize();
+    SkRect rect = SkRect::MakeXYWH(SkIntToScalar(canvasSize.fWidth-kDisplayWidth-kDisplayPadding),
+                                   SkIntToScalar(kDisplayPadding),
+                                   SkIntToScalar(kDisplayWidth), SkIntToScalar(kDisplayHeight));
+    SkPaint paint;
+    canvas->save();
+
+    canvas->clipRect(rect);
+    paint.setColor(SK_ColorBLACK);
+    canvas->drawRect(rect, paint);
+    // draw the 16ms line
+    paint.setColor(SK_ColorLTGRAY);
+    canvas->drawLine(rect.fLeft, rect.fBottom - kBaseMS*kPixelPerMS,
+                     rect.fRight, rect.fBottom - kBaseMS*kPixelPerMS, paint);
+    paint.setColor(SK_ColorRED);
+    paint.setStyle(SkPaint::kStroke_Style);
+    canvas->drawRect(rect, paint);
+
+    int x = SkScalarTruncToInt(rect.fLeft) + kGraphPadding;
+    const int xStep = 2;
+    const int startY = SkScalarTruncToInt(rect.fBottom);
+    int i = fCurrentMeasurement;
+    do {
+        int endY = startY - (int)(fMeasurements[i] * kPixelPerMS + 0.5);  // round to nearest value
+        canvas->drawLine(SkIntToScalar(x), SkIntToScalar(startY),
+                         SkIntToScalar(x), SkIntToScalar(endY), paint);
+        i++;
+        i &= (kMeasurementCount - 1);  // fast mod
+        x += xStep;
+    } while (i != fCurrentMeasurement);
 
     canvas->restore();
 }
 
-void VulkanViewer::onIdle(float dt) {
+void VulkanViewer::onIdle(double ms) {
+    // Record measurements
+    fMeasurements[fCurrentMeasurement++] = ms;
+    fCurrentMeasurement &= (kMeasurementCount - 1);  // fast mod
+    SkASSERT(fCurrentMeasurement < kMeasurementCount);
+
     fWindow->onPaint();
 }