Remove PlatformGestureEvent in favour of using WebGestureEvent

third_party/WebKit/Source/platform/WebGestureEvent.cpp

+#include "public/platform/WebGestureEvent.h"
+
+namespace blink {
+
+float WebGestureEvent::deltaXInRootFrame() const {
+  if (type == WebInputEvent::GestureScrollBegin)
+    return data.scrollBegin.deltaXHint / frameScale;
+  DCHECK(type == WebInputEvent::GestureScrollUpdate);
+  return data.scrollUpdate.deltaX / frameScale;
+}
+
+float WebGestureEvent::deltaYInRootFrame() const {
+  if (type == WebInputEvent::GestureScrollBegin)
+    return data.scrollBegin.deltaYHint / frameScale;
+  DCHECK(type == WebInputEvent::GestureScrollUpdate);
+  return data.scrollUpdate.deltaY / frameScale;
+}
+
+WebGestureEvent::ScrollUnits WebGestureEvent::deltaUnits() const {
+  if (type == WebInputEvent::GestureScrollBegin)
+    return data.scrollBegin.deltaHintUnits;
+  if (type == WebInputEvent::GestureScrollUpdate)
+    return data.scrollUpdate.deltaUnits;
+  DCHECK(type == WebInputEvent::GestureScrollEnd);
+  return data.scrollEnd.deltaUnits;
+}
+
+float WebGestureEvent::pinchScale() const {
+  DCHECK(type == WebInputEvent::GesturePinchUpdate);
+  return data.pinchUpdate.scale;
+}
+
+WebGestureEvent::InertialPhaseState WebGestureEvent::inertialPhase() const {
+  if (type == WebInputEvent::GestureScrollBegin)
+    return data.scrollBegin.inertialPhase;
+  if (type == WebInputEvent::GestureScrollUpdate)
+    return data.scrollUpdate.inertialPhase;
+  DCHECK(type == WebInputEvent::GestureScrollEnd);
+  return data.scrollEnd.inertialPhase;
+}
+
+bool WebGestureEvent::synthetic() const {
+  if (type == WebInputEvent::GestureScrollBegin)
+    return data.scrollBegin.synthetic;
+  DCHECK(type == WebInputEvent::GestureScrollEnd);
+  return data.scrollEnd.synthetic;
+}
+
+float WebGestureEvent::velocityX() const {
+  if (type == WebInputEvent::GestureScrollUpdate)
+    return data.scrollUpdate.velocityX;
+  DCHECK(type == WebInputEvent::GestureFlingStart);
+  return data.flingStart.velocityX;
+}
+
+float WebGestureEvent::velocityY() const {
+  if (type == WebInputEvent::GestureScrollUpdate)
+    return data.scrollUpdate.velocityY;
+  DCHECK(type == WebInputEvent::GestureFlingStart);
+  return data.flingStart.velocityY;
+}
+
+WebFloatSize WebGestureEvent::tapAreaInRootFrame() const {
+  if (type == WebInputEvent::GestureTwoFingerTap) {
+    return WebFloatSize(data.twoFingerTap.firstFingerWidth / frameScale,
+                        data.twoFingerTap.firstFingerHeight / frameScale);
+  } else if (type == WebInputEvent::GestureLongPress ||
+             type == WebInputEvent::GestureLongTap) {
+    return WebFloatSize(data.longPress.width / frameScale,
+                        data.longPress.height / frameScale);
+  } else if (type == WebInputEvent::GestureTap ||
+             type == WebInputEvent::GestureTapUnconfirmed) {
+    return WebFloatSize(data.tap.width / frameScale,
+                        data.tap.height / frameScale);
+  } else if (type == WebInputEvent::GestureTapDown) {
+    return WebFloatSize(data.tapDown.width / frameScale,
+                        data.tapDown.height / frameScale);
+  } else if (type == WebInputEvent::GestureShowPress) {
+    return WebFloatSize(data.showPress.width / frameScale,
+                        data.showPress.height / frameScale);
+  }
+  // This function is called for all gestures and determined if the tap
+  // area is empty or not; so return an empty rect here.
+  return WebFloatSize();
+}
+
+WebFloatPoint WebGestureEvent::positionInRootFrame() const {
+  return WebFloatPoint((x / frameScale) + frameTranslate.x,
+                       (y / frameScale) + frameTranslate.y);
+}
+
+int WebGestureEvent::tapCount() const {
+  DCHECK(type == WebInputEvent::GestureTap);
+  return data.tap.tapCount;
+}
+
+void WebGestureEvent::applyTouchAdjustment(WebFloatPoint rootFrameCoords) {
+  frameTranslate.x = rootFrameCoords.x - (x / frameScale);

[majidvp, 2016/12/15 17:40:46]

nit: the original method had a comment which was insightful. Can we
keep that please?

[dtapuska, 2016/12/15 21:29:39]

Done.

+  frameTranslate.y = rootFrameCoords.y - (y / frameScale);
+}
+
+void WebGestureEvent::flattenTransform() {
+  if (frameScale != 1.0) {
+    switch (type) {
+      case WebInputEvent::GestureScrollBegin:
+        data.scrollBegin.deltaXHint /= frameScale;
+        data.scrollBegin.deltaYHint /= frameScale;
+        break;
+      case WebInputEvent::GestureScrollUpdate:
+        data.scrollUpdate.deltaX /= frameScale;
+        data.scrollUpdate.deltaY /= frameScale;
+        break;
+      case WebInputEvent::GestureTwoFingerTap:
+        data.twoFingerTap.firstFingerWidth /= frameScale;
+        data.twoFingerTap.firstFingerHeight /= frameScale;
+        break;
+      case WebInputEvent::GestureLongPress:
+      case WebInputEvent::GestureLongTap:
+        data.longPress.width /= frameScale;
+        data.longPress.height /= frameScale;
+        break;
+      case WebInputEvent::GestureTap:
+      case WebInputEvent::GestureTapUnconfirmed:
+        data.tap.width /= frameScale;
+        data.tap.height /= frameScale;
+        break;
+      case WebInputEvent::GestureTapDown:
+        data.tapDown.width /= frameScale;
+        data.tapDown.height /= frameScale;
+        break;
+      case WebInputEvent::GestureShowPress:
+        data.showPress.width /= frameScale;
+        data.showPress.height /= frameScale;
+        break;
+      default:
+        break;
+    }
+  }
+
+  x = (x / frameScale) + frameTranslate.x;

[mustaq, 2016/12/15 19:25:46]

Any way we can do these transforms in a common place? Since frameScale &
frameTranslate belong to WebInputEvent, perhaps add transform methods scale(&x,
&y) and translate(&x, &y) there. Plus: can it possibly hide frameScale &
frameTranslate members in WebInputEvent?

[dtapuska, 2016/12/15 21:29:39]

I think that adding inline for div operators will kind of hide the math. I think
it is easier to read this way.

[mustaq, 2016/12/15 22:16:13]

I didn't mean operator overload, sorry for being too concise. Let me elaborate:

- Scaling is atomic for x- & y-dimensions. Same for translation: we won't expect
translation along one dimension only. So it's logical to pack x & y mods in a
function to avoid future mistakes.

- I find it more readable too: instead of Lines 128 & 129 above,
    scale(data.tapDown.width, data.tapDown.height);
seems better.

- Scale and/or translate operations have been done so many times here. They will
most likely be used in other event types too. Not repeating the logic everywhere
seems better.

- This last point is debatable: subclasses of WebInputEvent may not need to
access the scale & translate parameters after that.

Are you convinced now?

+  y = (y / frameScale) + frameTranslate.y;
+  frameTranslate.x = 0;
+  frameTranslate.y = 0;
+  frameScale = 1;
+}
+
+}  // namespace blink