Touch input support for Windows

Had to add some logic to avoid touch and mouse cross-talk, because
(at least on my laptop), the touch screen generates both kinds of
events.

This seems really useful [1] for the many [2] Skia developers with
touch-enabled Windows devices.

----------
1: No, not really.
2: N = 1?

Bug: skia:
Change-Id: Ib888bf4198f2cc0a29a31581ec4b64d3d9008c33
Reviewed-on: https://skia-review.googlesource.com/18920
Reviewed-by: Yuqian Li <liyuqian@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>

include/views/SkTouchGesture.h

@@ -39,6 +39,7 @@ public:
 
     bool isActive() { return fFlinger.isActive(); }
     void stop() { fFlinger.stop(); }
+    bool isBeingTouched() { return kEmpty_State != fState; }
 
     const SkMatrix& localM();
     const SkMatrix& globalM() const { return fGlobalM; }

src/views/SkTouchGesture.cpp

@@ -209,10 +209,8 @@ void SkTouchGesture::touchMoved(void* owner, float x, float y) {
 
     int index = this->findRec(owner);
     if (index < 0) {
-        // not found, so I guess we should add it...
-        SkDebugf("---- add missing begin\n");
-        this->appendNewRec(owner, x, y);
-        index = fTouches.count() - 1;
+        SkDebugf("---- ignoring move without begin\n");
+        return;
     }
 
     Rec& rec = fTouches[index];
@@ -220,7 +218,7 @@ void SkTouchGesture::touchMoved(void* owner, float x, float y) {
     // not sure how valuable this is
     if (fTouches.count() == 2) {
         if (close_enough_for_jitter(rec.fLastX, rec.fLastY, x, y)) {
-//            SkDebugf("--- drop touchMove, withing jitter tolerance %g %g\n", rec.fLastX - x, rec.fLastY - y);
+//            SkDebugf("--- drop touchMove, within jitter tolerance %g %g\n", rec.fLastX - x, rec.fLastY - y);
             return;
         }
     }

tools/viewer/Viewer.cpp

@@ -251,6 +251,7 @@ Viewer::Viewer(int argc, char** argv, void* platformData)
     , fColorMode(ColorMode::kLegacy)
     , fColorSpacePrimaries(gSrgbPrimaries)
     , fZoomLevel(0.0f)
+    , fGestureDevice(GestureDevice::kNone)
 {
     static SkTaskGroup::Enabler kTaskGroupEnabler;
     SkGraphics::Init();
@@ -819,6 +820,9 @@ void Viewer::onPaint(SkCanvas* canvas) {
 }
 
 bool Viewer::onTouch(intptr_t owner, Window::InputState state, float x, float y) {
+    if (GestureDevice::kMouse == fGestureDevice) {
+        return false;
+    }
     void* castedOwner = reinterpret_cast<void*>(owner);
     switch (state) {
         case Window::kUp_InputState: {
@@ -834,11 +838,15 @@ bool Viewer::onTouch(intptr_t owner, Window::InputState state, float x, float y)
             break;
         }
     }
+    fGestureDevice = fGesture.isBeingTouched() ? GestureDevice::kTouch : GestureDevice::kNone;
     fWindow->inval();
     return true;
 }
 
 bool Viewer::onMouse(float x, float y, Window::InputState state, uint32_t modifiers) {
+    if (GestureDevice::kTouch == fGestureDevice) {
+        return false;
+    }
     switch (state) {
         case Window::kUp_InputState: {
             fGesture.touchEnd(nullptr);
@@ -853,6 +861,7 @@ bool Viewer::onMouse(float x, float y, Window::InputState state, uint32_t modifi
             break;
         }
     }
+    fGestureDevice = fGesture.isBeingTouched() ? GestureDevice::kMouse : GestureDevice::kNone;
     fWindow->inval();
     return true;
 }

tools/viewer/Viewer.h

@@ -91,7 +91,14 @@ private:
 
     sk_app::CommandSet     fCommands;
 
+    enum class GestureDevice {
+        kNone,
+        kTouch,
+        kMouse,
+    };
+
     SkTouchGesture         fGesture;
+    GestureDevice          fGestureDevice;
 
     // identity unless the window initially scales the content to fit the screen.
     SkMatrix               fDefaultMatrix;

tools/viewer/sk_app/win/Window_win.cpp

@@ -114,6 +114,7 @@ bool Window_win::init(HINSTANCE hInstance) {
     }
 
     SetWindowLongPtr(fHWnd, GWLP_USERDATA, (LONG_PTR)this);
+    RegisterTouchWindow(fHWnd, 0);
 
     return true;
 }
@@ -196,6 +197,7 @@ static uint32_t get_modifiers(UINT message, WPARAM wParam, LPARAM lParam) {
             if (wParam & MK_SHIFT) {
                 modifiers |= Window::kShift_ModifierKey;
             }
+            break;
     }
 
     return modifiers;
@@ -296,6 +298,34 @@ LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
                                                 get_modifiers(message, wParam, lParam));
             break;
 
+        case WM_TOUCH: {
+            uint16_t numInputs = LOWORD(wParam);
+            std::unique_ptr<TOUCHINPUT[]> inputs(new TOUCHINPUT[numInputs]);
+            if (GetTouchInputInfo((HTOUCHINPUT)lParam, numInputs, inputs.get(),
+                                  sizeof(TOUCHINPUT))) {
+                RECT rect;
+                GetClientRect(hWnd, &rect);
+                for (uint16_t i = 0; i < numInputs; ++i) {
+                    TOUCHINPUT ti = inputs[i];
+                    Window::InputState state;
+                    if (ti.dwFlags & TOUCHEVENTF_DOWN) {
+                        state = Window::kDown_InputState;
+                    } else if (ti.dwFlags & TOUCHEVENTF_MOVE) {
+                        state = Window::kMove_InputState;
+                    } else if (ti.dwFlags & TOUCHEVENTF_UP) {
+                        state = Window::kUp_InputState;
+                    } else {
+                        continue;
+                    }
+                    // TOUCHINPUT coordinates are in 100ths of pixels
+                    // Adjust for that, and make them window relative
+                    LONG tx = (ti.x / 100) - rect.left;
+                    LONG ty = (ti.y / 100) - rect.top;
+                    eventHandled = window->onTouch(ti.dwID, state, tx, ty) || eventHandled;
+                }
+            }
+        } break;
+
         default:
             return DefWindowProc(hWnd, message, wParam, lParam);
     }